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Handbook of Lighting Design E Edition Rüdiger Ganslandt Harald Hofmann Vieweg 1,70 m 10˚ 20˚ 45˚ 45˚ 1,20 m 15˚ 25˚ 40˚ 90˚

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Page 1: ERCO HANDBOOK

Handbook ofLighting Design

E EditionRüdiger GanslandtHarald Hofmann

Vieweg

1,70 m

0˚10˚

20˚45˚

45˚

1,20 m

15˚ 25˚ 40˚

90˚

Page 2: ERCO HANDBOOK

Rüdiger GanslandtBorn in 1955. Studied German, Art and theHistory of Art in Aachen, Germany. Member of the project team on ‘imaginaryarchitecture’. Book publications on topicsrelating to sciences and humanities, article on lighting design. Joined Erco in1987, work on texts and didactic concepts. Lives in Lüdenscheid, Germany.

Harald HofmannBorn in 1941 in Worms, Germany. StudiedElectrical Engineering at Darmstadt Uni-versity of Technology from 1961 to 1968.Gained a doctorate in 1975. Worked as an educator and researcher in the LightingTechnology department at DarmstadtUniversity of Technology until 1978.Joined Erco in 1979 as Head of LightingTechnology. Professor of Lighting Techno-logy in the Faculty of Architecture at the Darmstadt University of Technologysince 1997.

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Title Handbook of Lighting Design

Authors Rüdiger GanslandtHarald Hofmann

Layout and otl aicher andgraphic design Monika Schnell

Drawings otl aicherReinfriede BettrichPeter GrafDruckhaus Maack

Reproduction Druckhaus Maack, LüdenscheidOffsetReproTechnik, BerlinReproservice Schmidt, Kempten

Setting/printing Druckhaus Maack, Lüdenscheid

Book binding C. FikentscherGroßbuchbinderei Darmstadt

© ERCO Leuchten GmbH, LüdenscheidFriedr. Vieweg & Sohn Verlagsgesell-schaft mbH, Braunschweig/Wiesbaden1. edition 1992

The Vieweg publishing company is a Ber-telsmann International Group company.

All rights reserved. No part of this publi-cation may be reproduced in any form orby any means without permission fromthe publisher. This applies in particular to(photo)copying, translations, microfilmsand saving or processing in electronic systems.

Printed in Germany

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Handbook ofLighting Design

E EditionRüdiger GanslandtHarald Hofmann

Vieweg

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About this book Wide interest has developed in light andlighting, not least because the growingawareness of architectural quality has gi-ven rise to an increased demand for good architectural lighting. Standardisedlighting concepts may have sufficed to light the concrete architecture of therecent past, but the varied and distinctivearchitecture of modern-day buildings requires equally differentiated and distinc-tive lighting.

An extensive range of light sources and luminaires are available for this task;with technical progress the scope oflighting technology has expanded, andthis has in turn led to the development of increasingly more specialised lightingequipment and tools. It is this fact that makes it increasingly difficult for thelighting designer to be adequately informed regarding the comprehensiverange of lamps and luminaires availableand to decide on the correct technical solution to meet the lighting requirementsof a specific project.

The Handbook of Lighting Design covers the basic principles and practice of architectural lighting. It exists as much as a teaching aid, e.g. for studentsof architecture, as a reference book forlighting designers. The Handbook doesnot intend to compete with the existingcomprehensive range of specialist literature on lighting engineering, nor tobe added to the limited number of beautifully illustrated volumes containingfinished projects. The Handbook aims to approach and deal with the subject ofarchitectural lighting in a practical

and comprehensible manner. Backgroundinformation is provided through a chapterdedicated to the history of lighting. The second part of the Handbook dealswith the basics of lighting technologyand surveys light sources, control gearand luminaires available. The third partdeals with concepts, strategies and theprocesses involved in lighting design. In the fourth part there is a comprehensivecollection of design concepts for the mostfrequent requirements of interior lighting. The glossary, index and bibliography provided to assist users of this Handbookin their daily work facilitate the search forinformation or further literature.

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Foreword

1.0 History

1.1 The history of architectural lighting 12

1.1.1 Daylight architecture 121.1.2 Artificial lighting 131.1.3 Science and lighting 151.1.4 Modern light sources 161.1.4.1 Gas lighting 171.1.4.2 Electrical light sources 181.1.5 Quantitative lighting design 221.1.6 Beginnings of a new age kind lighting design 221.1.6.1 The influence of stage lighting 241.1.6.2 Qualitative lighting design 241.1.6.3 Lighting engineering and lighting design 25

2.0 Basics

2.1 Perception 28

2.1.1 Eye and camera 282.1.2 Perceptual psychology 292.1.2.1 Constancy 312.1.2.2 Laws of gestalt 332.1.3 Physiology of the eye 362.1.4 Objects of peception 38

2.2 Terms and units 40

2.2.1 Luminous flux 402.2.2 Luminous efficacy 402.2.3 Quantity of light 402.2.4 Luminous intensity 402.2.5 Illuminance 422.2.6 Exposure 422.2.7 Luminance 42

2.3 Light and light sources 43

2.3.1 Incandescent lamps 452.3.1.1 Halogen lamps 492.3.2 Discharge lamps 522.3.2.1 Fluorescent lamps 532.3.2.2 Compact fluorescent lamps 542.3.2.3 High-voltage fluorescent tubes 552.3.2.4 Low-pressure sodium lamps 562.3.2.5 High-pressure mercury lamps 572.3.2.6 Self-ballasted mercury lamps 582.3.2.7 Metal halide lamps 592.3.2.8 High-pressure sodium lamps 60

2.4 Control gear and control equipment 65

2.4.1 Control gear for discharge lamps 652.4.1.1 Fluorescent lamps 652.4.1.2 Compact fluorescent lamps 662.4.1.3 High-voltage fluorescent tubes 662.4.1.4 Low-pressure sodium lamps 662.4.1.5 High-pressure mercury lamps 662.4.1.6 Metal halide lamps 672.4.1.7 High-pressure sodium lamps 672.4.2 Compensation and wiring of discharge lamps 672.4.3 Radio-interference suppression and limiting other

interference 672.4.4 Transformers for low-voltage installations 682.4.5 Controlling brightness 712.4.5.1 Incandescent and halogen lamps 71

Contents

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2.4.5.2 Low-voltage halogen lamps 712.4.5.3 Fluorescent lamps 712.4.5.4 Compact fluorescent lamps 722.4.5.5 Other discharge lamps 722.4.6 Remote control 722.4.7 Lighting control systems 722.4.7.1 Lighting control systems for theatrical effects 73

2.5 Light – qualities and features 74

2.5.1 Quantity of light 742.5.2 Diffuse light and directed light 762.5.2.1 Modelling 772.5.2.2 Brilliance 782.5.3 Glare 792.5.4 Luminous colour and colour rendering 83

2.6 Controlling light 85

2.6.1 The principles of controlling light 852.6.1.1 Reflection 852.6.1.2 Transmission 852.6.1.3 Absorption 872.6.1.4 Refraction 872.6.1.5 Interference 872.6.2 Reflectors 882.6.2.1 Parabolic reflectors 892.6.2.2 Darklight reflectors 902.6.2.3 Spherical reflectors 902.6.2.4 Involute reflectors 902.6.2.5 Elliptical reflectors 902.6.3 Lens systems 912.6.3.1 Collecting lenses 912.6.3.2 Fresnel lenses 912.6.3.3 Projecting systems 912.6.4 Prismatic systems 922.6.5 Accessories 92

2.7 Luminaires 94

2.7.1 Stationary luminaires 942.7.1.1 Downlights 942.7.1.2 Uplights 972.7.1.3 Louvred luminaires 972.7.1.4 Washlights 1002.7.1.5 Integral luminaires 1012.7.2 Movable luminaires 1022.7.2.1 Spotlights 1022.7.2.2 Wallwashers 1032.7.3 Light structures 1042.7.4 Secondary reflector luminaires 1052.7.5 Fibre optic systems 105

3.0 Lighting design

3.1 Lighting design concepts 110

3.1.1 Quantitative lighting design 1103.1.2 Luminance-based design 1123.1.3 The principles of perception-oriented lighting design 1153.1.3.1 Richard Kelly 1153.1.3.2 William Lam 1173.1.3.3 Architecture and atmosphere 118

3.2 Qualitative lighting design 119

3.2.1 Project analysis 1193.2.1.1 Utilisation of space 1193.2.1.2 Psychological requirements 1223.2.1.3 Architecture and atmosphere 122

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3.2.2 Project development 1233.3 Practical planning 126

3.3.1 Lamp selection 1263.3.1.1 Modelling and brilliance 1273.3.1.2 Colour rendering 1273.3.1.3 Luminous colour and colour temperature 1283.3.1.4 Luminous flux 1283.3.1.5 Efficiency 1283.3.1.6 Brightness control 1303.3.1.7 Ignition and re-ignition 1303.3.1.8 Radiant and thermal load 1303.3.2 Luminaire selection 1323.3.2.1 Standard product or custom design 1323.3.2.2 Integral or additive lighting 1323.3.2.3 Stationary or movable lighting 1363.3.2.4 General lighting or differentiated lighting 1363.3.2.5 Direct or indirect lighting 1363.3.2.6 Horizontal and vertical lighting 1383.3.2.7 Lighting working areas and floors 1383.3.2.8 Wall lighting 1393.3.2.9 Ceiling lighting 1413.3.2.10 Luminance limitation 1413.3.2.11 Safety requirements 1433.3.2.12 Relation to acoustics and air conditioning 1433.3.2.13 Accessories 1433.3.2.14 Lighting control and theatrical effects 1443.3.3 Lighting layout 1443.3.4 Switching and lighting control 1503.3.5 Installation 1523.3.5.1 Ceiling mounting 1523.3.5.2 Wall and floor mounting 1543.3.5.3 Suspension systems 1543.3.6 Calculations 1543.3.6.1 Utilisation factor method 1543.3.6.2 Planning based on specific connected load 1573.3.6.3 Point illuminance 1583.3.6.4 Lighting costs 1593.3.7 Simulation and presentation 1603.3.8 Measuring lighting installations 1683.3.9 Maintenance 169

4.0 Examples of lighting concepts

4.1 Foyers 1734.2 Lift lobbies 1804.3 Corridors 1844.4 Staircases 1884.5 Team offices 1924.6 Cellular offices 1984.7 Executive offices 2034.8 Conference rooms 2074.9 Auditoriums 2134.10 Canteens 2174.11 Cafés, bistros 2214.12 Restaurants 2254.13 Multifunctional spaces 2294.14 Museums, showcases 2364.15 Museum, galleries 2414.16 Vaulted ceilings 2494.17 Sales areas, boutiques 2524.18 Sales areas, counters 2564.19 Administration buildings, public areas 2594.20 Exhibitions 264

5.0 Appendix

Illuminance recommendations 270Classification of lamps 271Glossary 272, bibliography 282, acknowledgements 286, index 287

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History1.0

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For the most part of the history of mankind,from the origins of man up to the 18.century, there were basically two sourcesof light available. The older one of thesetwo is daylight, the medium by whichwe see and to whose properties the eye hasadapted over millions of years. A considerabletime elapsed before the stone age, withits development of cultural techniques andtools, added the flame as a second, artificial light source. From this timeon lighting conditions remained the same for a considerable time. The paintings in the cave of Altamira were created to beviewed under the same light as Renaissanceand Baroque paintings.

Lighting was limited to daylight andflame and it was for this very reason thatman has continued to perfect the appli-cation of these two light sources for tensof thousands of years.

1.1.1 Daylight architecture

In the case of daylight this meant consi-stently adapting architecture to the requirements for lighting with natural light.Entire buildings and individual roomswere therefore aligned to the incidence ofthe sun’s rays. The size of the rooms was also determined by the availability ofnatural lighting and ventilation. Differentbasic types of daylight architecture developed in conjunction with the lightingconditions in the various climatic zonesof the globe. In cooler regions with a predominantly overcast sky we see the development of buildings with large, tallwindows to allow as much light into thebuilding as possible. It was found that diffuse celestial light produced uniformlighting; the problems inherent to brightsunshine – cast shadow, glare and overheating of interior spaces – were restricted to a few sunny days in the yearand could be ignored.

In countries with a lot of sunshinethese problems are critical. A majority of the buildings here have small windows located in the lower sections of the buil-dings and the exterior walls are highly reflective. This means that hardly any directsunlight can penetrate the building. Eventoday the lighting is effected in the mainby the light reflected from the building’ssurfaces, the light being dispersed in the course of the reflection process and alarge proportion of its infrared componentdissipated.

When it came to the question of whetherthere was sufficient light, aspects relating to aesthetic quality and perceptualpsychology were also taken into accountwhen dealing with daylight, which is evident in the way architectural details aretreated. Certain elements were designeddifferently according to the light availableto promote the required spatial effectthrough the interplay of light and shadow.In direct sunlight reliefs, ledges and the

12

1.1 History1.1.1 Daylight architecture

The history of architecturallighting

1.1

Daylight architecture: large, tall windows.

Sunlight architecture: small, low windows, reflective outer walls.

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1.1 History1.1.2 Artifical lighting

fluting on columns have a three-dimensionaleffect even if they are of shallow depth.Such details require far more depth underdiffuse light to achieve the same effect.Facades in southern countries thereforeonly needed shallow surface structures,whereas the architecture of more northern latitudes – and the design of interior spaces – was dependent on morepronounced forms and accentuationthrough colour to underline the structureof surfaces.

But light does not only serve to renderspatial bodies three-dimensional. It is anexcellent means for controlling our perception on a psychological level. In oldEgyptian temples – e.g. in the sun temple of Amun Re in Karnak or in Abu Simbel –you will not find light in the form of uniform ambient lighting, but as a meansto accentuate the essential – colonnadesthat gradually become darker allowthe viewer to adapt to lower lighting levels,the highlighted image of the god thenappearing overwhelmingly bright in con-trast. An architectural construction canfunction similar to an astronomical clock,with special lighting effects only occurringon significant days or during particularperiods in the year, when the sun rises or sets, or at the summer or the winter solstice.

In the course of history the skill to createpurposefully differentiated daylightingeffects has been continually perfected,reaching a climax in the churches ofthe Baroque period, – e.g. the pilgrimagechurch in Birnau or the pilgrimage churchdesigned by Dominikus Zimmermann in Upper Bavaria – , where the visitor’sgaze is drawn from the diffuse brightnessof the nave towards the brightly lit altar area, where intricate wood carvingsdecorated in gold sparkle and stand out in relief.

1.1.2 Artificial lighting

A similar process of perfection also tookplace in the realm of artificial lighting, a development that was clearly confined bythe inadequate luminous power providedby the light sources available.

The story began when the flame, thesource of light, was separated from fire,the source of warmth - burning brancheswere removed from the fire and used fora specific purpose. It soon became obviousthat it was an advantage to select piecesof wood that combust and emit light particularly well, and the branch was replaced by especially resinous pine wood.The next step involved not only relying on a natural feature of the wood, but, inthe case of burning torches, to applyflammable material to produce more lightartificially. The development of the oillamp and the candle meant that man thenhad compact, relatively safe light sourcesat his disposal; select fuels were used eco-

13

The influence of light onnorthern and southernarchitectural design. Inthe south spatial formsare aligned to the correlation of the steepangle of incident sun-light and light reflectedfrom the ground. In thenorth it is the lowangle of the sun’s raysthat affects the shapeof the buildings.

Greek oil lamp, a massitem in the ancientworld

Oil lamp made of brass

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1.1 History1.1.2 Artificial lighting

14

Lamps and burners da-ting back to the second half of the 19.century, copper engra-ving. Based on theconstruction of the Argand burner, the oillamp was adaptedthrough numeroustechnical innovationsto meet a wide varietyof requirements.The differences betweenlamps with flat wicksand those with themore efficient tubularwicks are clearly evi-dent. In later paraffinlamps the light fuel

was transported to theflame via the capillaryaction of the wickalone, earlier lampsthat used thick-bodiedvegetable oils requiredmore costly fuel supplysolutions involvingupturned glass bottlesor spring mechanisms.In the case of especi-ally volatile or thick-bodied oils there werespecial wickless lampsavailable that producedcombustible gaseousmixtures through the inherent vapourpressure produced by the volatile oil or byexternal compression.

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1.1 History1.1.3 Science and lighting

nomically in these cases, the torch holderwas reduced to the wick as a means oftransport for wax or oil.

The oil lamp, which was actually de-veloped in prehistoric times, representedthe highest form of lighting engineeringprogress for a very long time. The lamp itself – later to be joined by the candlestick– continued to be developed. All sorts of magnificent chandeliers and sconceswere developed in a wide variety of styles,but the flame, and its luminous power, remained unchanged.

Compared to modern day light sourcesthis luminous power was very poor, and artificial lighting remained a make-shift device. In contrast to daylight, whichprovided excellent and differentiatedlighting for an entire space, the brightnessof a flame was always restricted to its direct environment. People gathered around the element that provided light or positioned it directly next to the objectto be lit. Light, albeit weak, began to mark man’s night-time. To light interiorsbrightly after dark required large numbers of expensive lamps and fixtures,which were only conceivable for courtlygatherings. Up to the late 18th centuryarchitectural lighting as we know it today remained the exclusive domain of day-lighting.

1.1.3 Science and lighting

The reason why the development of effi-cient artficial light sources experienceda period of stagnation at this point in timelies in man’s inadequate knowledge in thefield of science. In the case of the oillamp, it was due to man’s false conceptionof the combustion process. Until the birth of modern chemistry, the belief laiddown by the ancient Greeks was taken to be true: during the burning process a substance called “phlogistos” was released.According to the Greeks, any materialthat could be burned therefore consistedof ash and phlogistos ( the classical elements of earth and fire), which were separated during the burning process –phlogistos was released as a flame, earthremained in the form of ash.

It is clear that the burning processcould not be optimised as long as beliefswere based on this theory. The role of oxidation had not yet been discovered. It was only through Lavoisier’s experimentsthat it became clear that combustion was a form of chemical action and thatthe flame was dependent on the presenceof air.

Lavoisier’s experiments were carriedout in the 1770s and in 1783 the new fin-dings were applied in the field of lighting.Francois Argand constructed a lamp thatwas to be named after him, the Argandlamp. This was an oil lamp with a tubularwick, whereby air supply to the flame was effected from within the tube as well as from the outer surface of the wick.

Improved oxygen supply together with anenlarged wick surface meant a huge andinstantaneous improvement in luminousefficiency. The next step involved surroun-ding wick and flame with a glass cylinder,whereby the chimney effect resulted in an increased through-put of air and a further increase in efficiency. The Argandlamp became the epitome of the oil lamp. Even modern day paraffin lamps workaccording to this perfected principle.

Optical instruments have been recognisedas aids to controlling light from very earlytimes. Mirrors are known to have beenused by ancient Greeks and Romans andthe theory behind their application setdown in writing. There is a tale about Archimedes setting fire to enemy shipsoff Syracuse using concave mirrors. And there are stories of burning glasses,in the form of water-filled glass spheres.

At the turn of the first millennium,there were a number of theoretical worksin Arabia and China concerning the effectof optical lenses. There is in fact concreteevidence of these lenses dating fromthe 13th century. They were predominantlyused in the form of magnifying glasses or spectacles as a vision aid. The materialfirst used was ground beryl. This costlysemi-precious stone was later replaced byglass, manufactured to a sufficiently clearquality. The German word for glasses is “Brille”, demonstrating a clear semanticlink to the original material used for thevision aid.

In the late 16th century the first tele-scopes were designed by Dutch lens grinders.In the 17th century these instrumentswere then perfected by Galileo, Keplerand Newton; microscopes and projectorequipment were then constructed.

At the same time, some basic theoriesabout the nature of light originated.Newton held the view that light wasmade up of numerous particles – a view that can be retraced to ancient time. Huygens, on the other hand, saw light asa phenomenon comprising waves. The twocompeting theories are substantiated by a series of optical phenomena and existedside by side. Today it is clear that light can neither be understood as a purely particle or wave-based phenomenon,but only through an understanding of thecombination of both ideas.

With the development of photometrics– the theory of how to measure light –and illuminances – through Boguer andLambert in the 18th century, the most essential scientific principles for workablelighting engineering were established. The application of these various correlatedfindings was restricted practically exclu-sively to the construction of optical in-struments such as the telescope and themicroscope, to instruments therefore thatallow man to observe, and are dependenton external light sources. The activecontrol of light using reflectors and lenses,known to be theoretically possible and

15

Christiaan Huygens. Isaac Newton.

Paraffin lamp with Argand burner.

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1.1 History1.1.4 Modern light sources

occasionally tested, was doomed to faildue to the shortcomings of the lightsources available.

In the field of domestic lighting thefact that there was no controllable, centrally situated light available was notconsidered to be a concern. It was com-pensated for by family gatherings aroundthe oil lamp in the evenings. This short-coming gave rise to considerable problemsin other areas, however. For example, in lighting situations where a considerabledistance between the light source and the object to be lit was required, aboveall, therefore, in street lighting and stagelighting, and in the area of signalling, especially in the construction of lighthouses.It was therefore not surprising that the Argand lamp, with its considerably improved luminous intensity not only served to light living-rooms, but was welcomed in the above-mentioned criticalareas and used to develop systems thatcontrol light.

This applied in the first place to streetand stage lighting, where the Argandlamp found application shortly after itsdevelopment. But the most important usewas for lighthouses, which had previouslybeen poorly lit by coal fires or by using a large number of oil lamps. The proposal to light lighthouses using systems compri-sing Argand lamps and parabolic mirrorswas made in 1785; six years later the ideawas used in France’s most prominentlighthouse in Cordouan. In 1820 AugustinJean Fresnel developed a composite system of stepped lens and prismatic ringswhich could be made large enough to concentrate the light from lighthouses;this construction was also first installedin Cordouan. Since then Fresnel lenses havebeen the basis for all lighthouse beaconsand have also been applied in numeroustypes of projectors.

1.1.4 Modern light sources

The Argand lamp marked the climax of a development which lasted tens of thou-sands of years, perfecting the use of theflame as a light source. The oil lamp at itsvery best, so to speak. Scientific progress,which rendered this latter developmentpossible, gave rise to the development of completely new light sources , whichrevolutionised lighting engineering at anincreasingly faster pace.

16

Beacon with Fresnellenses and Argand burners.

Augustin Jean Fresnel.

Fresnel lenses and Argand burners. Theinner section of the luminous beam is con-centrated via a steppedlens, the outer sectiondeflected by means of separate prismaticrings.

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1.1 History1.1.4 Modern light sources

1.1.4.1 Gas lighting

The first competitor to the Argand lamp wasgas lighting. People had known of the existence of combustible gases sincethe 17th century, but gaseous substanceswere first systematically understoodand produced within the framework ofmodern chemistry. A process for recoveringlighting gas from mineral coal was developed in parallel to the Argand lampexperimentation.

Towards the end of the 18th centurythe efficiency of gas lighting was demon-strated in a series of pilot projects – a lecturehall in Löwen lit by Jan Pieter Minckellaers;a factory, a private home and even an automobile lit by the English engineerWilliam Murdoch. This new light sourceachieved as yet unknown illuminance levels. It was, however, not yet possible tointroduce this new form of lighting on a large scale due to the costs involved inthe manufacture of the lighting gas and in removing the admittedly foul-smellingresidues. A number of small devices weredeveloped, so-called thermo-lamps,which made it possible to produce gas forlighting and heating in individual house-holds. These devices did not prove to be as successful as hoped. Gas lighting onlybecame an economic proposition with the coupling of coke recovery and gasproduction, then entire sections of townscould benefit from central gas supply.Street lighting was the first area to be connected to a central gas supply, followed gradually by public buildingsand finally private households.

As is the case with all other lightsources a series of technical developmentsmade gas lighting increasingly more efficient. Similar to the oil lamp a varietyof different burners were developedwhose increased flame sizes provided increased luminous intensity. The Argandprinciple involving the ring-shaped flamewith its oxygen supply from both sidescould also be applied in the case of gas lighting and in turn led to unsurpassedluminous efficacy.

The attempt to produce a surplus ofoxygen in the gas mixture by continuingto develop the Argand burner produced a surprising result. As all the carbon con-tained in the gas was burned off to pro-duce gaseous carbon dioxide, the glowingparticles of carbon that incorporated thelight produced by the flame were no longerevident; this gave rise to the extraor-dinarily hot, but barely glowing flame ofthe Bunsen burner. There was therefore a limit to the luminous intensity of self-luminous flames; for further increases in efficiency researchers had to fall backon other principles to produce light .

One possibility for producing highly efficientgas lighting was developed through thephenomenon of thermo-luminescence, theexcitation of luminescent material by

17

Lighting shop windowsusing gas light (around1870).

Carl Auer v. Welsbach.

Drummond’s limelight. The incandescentmantle as invented by Auer v. Welsbach.

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1.1 History1.1.4 Modern light sources

heating. In contrast to thermal radiation,luminous efficacy and colour appearancein this process were not solely dependenton the temperature, but also on the kindof material; more and whiter light was produced using temperature radiationmethods.

The first light source to work accordingto this principle was Drummond’s limelight, which was developed in 1826.This involved a piece of limestone beingexcited to a state of thermo-luminescencewith the aid of an oxy-hydrogen burner.Limelight is admittedly very effective, butrequires considerable manual control withthe result that it was used almost exclu-sively for effect lighting in the theatre. It was only in 1890 that Austrian chemistCarl Auer von Welsbach came up with a far more practical method for utilisingthermo-luminiscence. Auer von Welsbachsteeped a cylinder made of cotton fabric in a solution containing rare earths – sub-stances that, similar to limestone, emit a strong white light when heated. Theseincandescent mantles were applied toBunsen burners. On first ignition the cottonfabric burned, leaving behind nothing butthe rare earths – the incandescent mantle ineffect. Through the combination of theextremely hot flame of the Bunsen burnerand incandescent mantles comprising rareearths, the optimum was achieved in the field of gas lighting. Just as the Argandlamp continues to exist today in the form of the paraffin lamp, the incandescentor Welsbach mantle is still used for gaslighting, e.g. in camping lamps.

1.1.4.2 Electrical light sources

Incandescent gas light was doomed to gothe way of most lighting discoveries thatwere fated to be overtaken by new lightsources just as they are nearing perfection.This also applies to the candle, which only received an optimised wick in 1824to prevent it from smoking too much.Similarly, the Argand lamp was pipped atthe post by the development of gaslighting, and for lighting using incandescentmantles, which in turn had to competewith the newly developed forms of electriclight.

In contrast to the oil lamp and gaslighting, which both started life as weaklight sources and were developed to be-come ever more efficient, the electric lampembarked on its career in its brightestform. From the beginning of the 19thcentury it was a known fact that by crea-ting voltage between two carbon electrodesan extremely bright arc could be pro-duced. Similar to Drummond’s limelight,continuous manual adjustment was required, making it difficult for this newlight source to gain acceptance, added to the fact that arc lamps first had to beoperated on batteries, which was a costlybusiness.

18

Hugo Bremer’s arclamp. A simple springmechanism automati-cally controls the dis-tance between thefour carbon electrodesset in the shape of a V.

Jablotschkow’s versionof the arc lamp, ex-posed and with glassbulb.

Arc lighting at thePlace de la Concorde.

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1.1 History1.1.4 Modern light sources

19

Siemens’ arc lampdating back to 1868.According to the des-cription: an adjustablespotlight complete with“concave mirror, car-riage, stand and anti-dazzle screen" –the oldest luminaire in Siemens’ archives documented in the formof a drawing.

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1.1 History1.1.4 Modern light sources

About mid-century self-adjusting lampswere developed, thereby eliminating theproblem of manual adjustment. Generatorsthat could guarantee a continuous supplyof electricity were now also available. It was, however, still only possible to operateone arc lamp per power source; seriesconnection – “splitting the light”, as it wascalled – was not possible, as the differentburning levels of the individual lampsmeant that the entire series was quicklyextinguished. This problem was only solved in the 1870s. The simple solutionwas provided by Jablotschkow’s version of the arc lamp, which involved twoparallel carbon electrodes set in a plastercylinder and allowed to burn simulta-neously from the top downwards. A morecomplex, but also more reliable solutionwas provided by the differential lamp, developed in 1878 by Friedrich v. Hefner-Alteneck, a Siemens engineer, wherebycarbon supply and power constancy wereeffected via an electromagnetic system.

Now that light could be “divided up” thearc lamp became an extremely practicallight source, which not only found individual application, but was also usedon a wide scale. It was in fact appliedwherever its excellent luminous intensity could be put to good use – once again inlighthouses, for stage lighting; and, aboveall, for all forms of street and exteriorlighting. The arc lamp was not entirely suitable for application in private homes,however, because it tended to produce far too much light – a novelty in the fieldof lighting technology. It would takeother forms of electric lighting to replacegas lighting in private living spaces.

It was discovered at a fairly early stage,that electrical conductors heat up to pro-duce a sufficiently great resistance, andeven begin to glow; in 1802 – eight yearsbefore his spectacular presentation of thefirst arc lamp – Humphrey Davy demon-strated how he could make a platinum wireglow by means of electrolysis.

The incandescent lamp failed to esta-blish itself as a new light source for technical reasons, much the same as the arclamp. There were only a few substancesthat had a melting point high enough tocreate incandescence before melting.Moreover, the high level of resistance required very thin filaments, which weredifficult to produce, broke easily andburnt up quickly in the oxygen in the air.

First experiments made with platinumwires or carbon filaments did not producemuch more than minimum service life.The life time could only be extended whenthe filament – predominantly made of carbon or graphite at that time – wasprevented from burning up by surroundingit with a glass bulb, which was either evacuated or filled with inert gas.Pioneers in this field were Joseph WilsonSwan, who preceded Edison by six months with his graphite lamp, but above

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Heinrich Goebel, experi-mental incandescentlamps (carbon fila-ments in air-void eau-de-cologne bottles).

Joseph Wilson Swan,Swan’s version of theincandescent lampwith graphite filamentand spring base.

Thomas Alva Edison,Edison lamps, platinumand carbon filamentversion, as yet withoutthe typical screw cap.

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1.1 History1.1.4 Modern light sources

all Heinrich Goebel, who in 1854 producedincandescent lamps with a service life of 220 hours with the aid of carbonizedbamboo fibres and air-void eau-de-colognebottles.

The actual breakthrough, however, wasindeed thanks to Thomas Alva Edison,who in 1879 succeeded in developing anindustrial mass product out of the experimental constructions created by hispredecessors. This product correspondedin many ways to the incandescent lamp as we know it today – right down tothe construction of the screw cap. The filament was the only element thatremained in need of improvement. Edison first used Goebel’s carbon filamentcomprising carbonized bamboo. Latersynthetic carbon filaments extruded fromcellulose nitrate were developed. The lu-minous efficacy, always the main weaknessof incandescent lamps, could, however,only be substantially improved with the changeover to metallic filaments. This iswhere Auer von Welsbach, who had already made more efficient gas lightingpossible through the development of theincandescent mantle, comes into his ownonce again. He used osmium filamentsderived through a laborious sinteringprocess. The filaments did not prove to bevery stable, however, giving way to tantalumlamps, which were developed a little later and were considerably more robust.These were in turn replaced by lampswith filaments made of tungsten, a mate-rial still used for the filament wire inlamps today.

Following the arc lamp and the incandes-cent lamp, discharge lamps took theirplace as the third form of electric lighting.Again physical findings were availablelong before the lamp was put to anypractical use. As far back as the 17th century there were reports about luminousphenomena in mercury barometers. But it was Humphrey Davy once againwho gave the first demonstration of howa discharge lamp worked. In fact, at the beginning of the 18th century Davy ex-amined all three forms of electric lightingsystematically. Almost eighty years passed, however, before the first trulyfunctioning discharge lamps were actuallyconstructed, and it was only after the incandescent lamp had established itselfas a valid light source, that the first discharge lamps with the prime purposeof producing light were brought onto the market. This occured at around the turn of the century. One of these was the Moore lamp – a forerunner of the modern-day high voltage fluorescenttube. It consisted of long glass tubes ofvarious shapes and sizes, high voltage and a pure gas discharge process. Anotherwas the low-pressure mercury lamp,which is the equivalent of the fluorescentlamp as we know it today, except that ithad no fluorescent coating.

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Cooper-Hewitt’s low-pressure mercury lamp.This lamp workedmuch like a modern-day fluorescent tubebut did not containany fluorescent mate-rial, so only very littlevisible light was pro-duced. The lamp wasmounted in the centrelike a scale beam, be-cause it was ignited by tipping the tubes bymeans of a drawstring.

Theatre foyer lit byMoore lamps.

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1.1 History1.1.5 Quantitative lighting design1.1.6 Beginnings of new lighting design

The Moore lamp – like the high-voltage fluorescent tube today – was primarily used for contour lighting in archi-tectural spaces and for advertising purpo-ses; its luminous intensity was too low to be seriously used for functional lighting.The mercury vapour lamp, on the otherhand, had excellent luminous efficacy values, which immediately established it asa competitor to the relatively inefficientincandescent lamp. Its advantages were,however, outweighed by its inadequatecolour rendering properties, which meantthat it could only be used for simplelighting tasks.

There were two completely differentways of solving this problem. One possibilitywas to compensate for the missing spectral components in the mercury vapour discharge process by adding lumi-nous substances. The result was the flu-orescent lamp, which did produce goodcolour rendering and offered enhanced luminous efficacy due to the exploitationof the considerable ultra-violet emission.

The other idea was to increase thepressure by which the mercury vapourwas discharged. The result was moderatecolour rendering, but a considerable in-crease in luminous efficacy. Moreover, thismeant that higher light intensities could be achieved, which made the high-pressure mercury lamp a competitor to thearc lamp.

1.1.5 Quantitative lighting design

A good hundred years after scientific re-search into new light sources began all the standard lamps that we know todayhad been created, at least in their basicform. Up to this point in time, sufficientlight had only been available during daylight hours. From now on, artificiallight changed dramatically. It was no longera temporary expedient but a form of lighting to be taken seriously, rankingwith natural light.

Illuminance levels similar to those ofdaylight could technically now be pro-duced in interior living and working spacesor in exterior spaces, e.g. for the lightingof streets and public spaces, or for the floodlighting of buildings. Especially inthe case of street lighting, the temptationto turn night into day and to do awaywith darkness altogether was great. In theUnited States a number of projects wererealised in which entire towns were lit byan array of light towers. Floodlighting on this scale soon proved to have more dis-advantages than advantages due to glareproblems and harsh shadows. The days of this extreme form of exterior lightingwere therefore numbered.

Both the attempt to provide comprehen-sive street lighting and the failure ofthese attempts was yet another phase inthe application of artificial light. Whereas

inadequate light sources had been themain problem to date, lighting specialistswere then faced with the challenge of purposefully controlling excessiveamounts of light. Specialist engineersstarted to think about how much light was to be required in which situationsand what forms of lighting were to be applied.

Task lighting in particular was examinedin detail to establish how great an influence illuminance and the kind oflighting applied had on productivity. The result of these perceptual physiologicalinvestigations was a comprehensive work of reference that contained the illuminance levels required for certain visual tasks plus minimum colour renderingqualities and glare limitation require-ments.

Although this catalogue of standardswas designed predominantly as an aid for the planning of lighting for workplaces,it soon became a guideline for lighting in general, and even today determineslighting design in practice. As a planningaid it is almost exclusively quantity-oriented and should, therefore, not be regarded as a comprehensive planning aidfor all possible lighting tasks. The aim of standards is to manage the amount oflight available in an economic sense, based on the physiological research thathad been done on human visual require-ments.

The fact that the perception of an object is more than a mere visual task andthat, in addition to a physiological process,vision is also a psychological process, was disregarded. Quantitative lighting design is content with providing uniformambient lighting that will meet the re-quirements of the most difficult visualtask to be performed in the given space,while at the same time adhering to thestandards with regard to glare limitationand colour distortion. How we see archi-tecture, for instance, under a given light,whether its structure is clearly legible andits aesthetic quality has been enhanced by the lighting, goes beyond the realm ofa set of rules.

1.1.6 Beginnings of a new kind oflighting design

It was, therefore, not surprising thatalongside quantative lighting technologyand planning a new approach to designingwith light was developed, an approachthat was related far more intensely to architectural lighting and its inherentrequirements.

This developed in part within the framework of lighting engineering as itwas known. Joachim Teichmüller, founderof the Institute for Lighting Technologyin Karlsruhe, is a name that should be men-tioned here. Teichmüller defined the term “Lichtarchitektur” as architecture that

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American light tower(San José 1885).

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conceives light as a building material andincorporates it purposefully into the over-all architectural design. He also pointedout – and he was the first to do so – that,with regard to architectural lighting, artificial light can surpass daylight, if it isapplied purposefully and in a differentiatedway.

Lighting engineers still tended topractise a quantative lighting philiosophy.It was the architects who were now beginning to develop new concepts for architectural lighting. From time imme-morial, daylight had been the definingagent. The significance of light and shadowand the way light can structure a building is something every architect is familiar with. With the development ofmore efficient artificial light sources, the knowledge that has been gained of day-light technology was now joined by the scope offered by artificial light. Lightno longer only had an effect coming fromoutside into the building. It could light interior spaces, and now even light frominside outwards. When Le Corbusier described architecture as the “correct andmagnificent play of masses brought together in light”, this no longer only applied to sunlight, but also included theartificially lit interior space.

This new understanding of light hadspecial significance for extensively glazedfacades, which were not only openings to let daylight into the building, but gavethe architecture a new appearance atnight through artificial light. A Germanstyle of architecture known as “GläserneKette” in particular interpreted the buildingas a crystalline, self-luminous creation.Utopian ideas of glass architecture, luminous cities dotted with light towersand magnificent glazed structures, à laPaul Scheerbart, were reflected in a numberof equally visionary designs of spar-kling crystals and shining domes. A littlelater, in the 1920s, a number of glass architecture concepts were created; largebuildings such as industrial plants or department stores took on the appearanceof self-illuminating structures after dark, their facades divided up via the inter-change of dark wall sections and lightglazed areas. In these cases, lighting design clearly went far beyond the merecreation of recommended illuminances. It addressed the structures of the lit architecture. And yet even this approachdid not go far enough, because it regardedthe building as a single entity, to be viewed from outside at night, and dis-regarded users of the building and their visual needs.

Buildings created up to the beginningof the second world war were thereforecharacterised by what is, in part, highlydifferentiated exterior lighting. All this, however, made little difference to thetrend towards quantitative, unimaginativeinterior lighting, involving in the mainstandard louvred fittings.

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Joachim Teichmüller.

Wassili Luckhardt(1889–1972): Crystalon the sphere. Cultbuilding. Second ver-sion. Crayon, around1920.

J. Brinkmann, L. C. van derVlugt and Mart Stam:Van Nelle tobacco factory, Rotterdam 1926–30.

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In order to develop more far-reachingarchitectural lighting concepts, man had to become the third factor alongsidearchitecture and light. Perceptual psycho-logy provided the key. In contrast to physiological research, it was not simply aquestion of the quantitative limiting va-lues for the perception of abstract “visualtasks”. Man as a perceiving being was the focus of the research, the question ofhow reality perceived is reconstructed inthe process of seeing. These investigationssoon led to evidence that perception was not purely a process of reproducingimages, not a photographing of our environ-ment. Innumerable optical phenomenaproved that perception involves a complexinterpretation of surrounding stimuli, that eye and brain constructed rather thanreproduced an image of the world aroundus.

In view of these findings lighting acquired a totally new meaning. Light wasno longer just a physical quantity thatprovided sufficient illumination; it becamea decisive factor in human perception. Lighting was not only there to renderthings and spaces around us visible, it determined the priority and the way individual objects in our visual environmentwere seen.

1.1.6.1 The influence of stage lighting

Lighting technology focussing on man as aperceptive being acquired a number of essential impulses from stage lighting. In thetheatre, the question of illuminance levelsand uniform lighting is of minor impor-tance. The aim of stage lighting is not to render the stage or any of the technicalequipment it comprises visible; what the audience has to perceive is changing scenes and moods – light alone can beapplied on the same set to create the im-pression of different times of day, changesin the weather, frightening or romanticatmospheres.

Stage lighting goes much further in its intentions than architectural lightingdoes – it strives to create illusions, where-as architectural lighting is concerned with rendering real structures visible. Never-theless stage lighting serves as an examplefor architectural lighting. It identifies methods of producing differentiatedlighting effects and the instruments re-quired to create these particular effects –both areas from which architecturallighting can benefit. It is therefore notsurprising that stage lighting began toplay a significant role in the developmentof lighting design and that a large numberof well-known lighting designers have theirroots in theatre lighting.

1.1.6.2 Qualitative lighting design

A new lighting philosophy that no longerconfined itself exclusively to quantitative

aspects began to develop in the USA after the second world war. One of thepioneers in the field is without doubtRichard Kelly, who integrated existing ideasfrom the field of perceptual psychologyand stage lighting to create one uniformconcept.

Kelly broke away from the idea of uniform illuminance as the paramountcriterion of lighting design. He substitutedthe issue of quantity with the issue of different qualities of light, of a series offunctions that lighting had to meet toserve the needs of the perceiver. Kelly dif-ferentiated between three basic func-tions: ambient light , focal glow and playof brilliance.

Ambient light corresponded to whathad up to then been termed quantitativelighting. General lighting was providedthat was sufficient for the perception ofthe given visual tasks; these might include the perception of objects andbuilding structures, orientation within anenvironment or orientation while in motion.

Focal glow went beyond this generallighting and allowed for the needs of manas a perceptive being in the respective environment. Focal glow picked out relevantvisual information against a backgroundof ambient light; significant areas wereaccentuated and less relevant visual information took second place. In contrastto uniform lighting, the visual environ-ment was structured and could be perceivedquickly and easily. Moreover, the viewer’sattention could be drawn towards individual objects, with the result that focal glow not only contributed towardsorientation, but could also be used for the presentation of goods and aestheticobjects.

Play of brilliance took into accountthe fact that light does not only illuminateobjects and express visual information,but that it could become an object of contemplation, a source of information,in itself. In this third function light could also enhance an environment in an aesthetic sense – play of brilliance froma simple candle flame to a chandeliercould lend a prestigious space life andatmosphere.

These three basic lighting categoriesprovided a simple, but effective andclearly structured range of possibilitiesthat allowed lighting to address the architecture and the objects within an environment as well as the perceptual needsof the users of the space. Starting in the USA, lighting design began to changegradually from a purely technical disci-pline to an equally important and indis-pensible discipline in the architectural design process – the competent lightingdesigner became a recognised partner in the design team, at least in the case oflarge-scale, prestigious projects.

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Ambient light.

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1.1.6.3 Lighting engineering and lightingdesign

The growing demand for quality lightingdesign was accompanied by the demand for quality lighting equipment. Differen-tiated lighting required specialisedluminaires designed to cope with specificlighting tasks. You need completely diffe-rent luminaires to achieve uniform wash-light over a wall area, for example, than you do for accentuating one individualobject, or different ones again for the permanent lighting in a theatre foyerthan for the variable lighting required ina multi-purpose hall or exhibition space.

The development of technical possibi-lities and lighting application led to a productive correlation: industry had tomeet the designers’ demands for new luminaires, and further developments inthe field of lamp technology and luminairedesign were promoted to suit particularapplications required by the lighting designers.

New lighting developments served toallow spatial differentiation and more flexible lighting. Exposed incandescent andfluorescent lamps were replaced by a variety of specialised reflector luminaires,providing the first opportunity to directlight purposefully into certain areas or onto objects – from the uniform lightingof extensive surfaces using wall or ceilingwashers to the accentuation of a preciselydefined area by means of reflector spot-lights. The development of track lightingopened up further scope for lighting design, because it allowed enormous flexibi-lity. Lighting installations could be adap-ted to meet the respective requirementsof the space.

Products that allowed spatial differen-tiation were followed by new developmentsthat offered time-related differentiation:lighting control systems. With the useof compact control systems it has becomepossible to plan lighting installations that not only offer one fixed application,but are able to define a range of lightscenes. Each scene can be adjusted to suitthe requirements of a particular situation.This might be the different lighting conditions required for a podiumdiscussion or for a slide show, but it mightalso be a matter of adapting to changeswithin a specific environment: the changingintensity of daylight or the time of day.Lighting control systems are therefore alogical consequenceof spatial differentiation,allowing a lighting installation to be utilised to the full – a seamless transitionbetween individual scenes, which is simplynot feasible via manual switching.

There is currently considerable researchand development being undertaken in the field of compact light sources: amongthe incandescents the halogen lamp,whose sparkling, concentrated light provides new concepts for display lighting.Similar qualities are achieved in the field

of discharge lamps with metal halidesources. Concentrated light can be appliedeffectively over larger distances. The third new development is the compactfluorescent lamp, which combines the advantages of the linear fluorescent withsmaller volume, thereby achieving improved optical control, ideally suited toenergy-efficient fluorescent downlights,for example.

All this means that lighting designershave a further range of tools at their disposal for the creation of differentiatedlighting to meet the requirements of the specific situation and the perceptualneeds of the people using the space. It can be expected in future that progressin the field of lighting design will dependon the continuing further development of light sources and luminaires, but aboveall on the consistent application of this‘hardware’ in the interest of qualitativelighting design. Exotic solutions – usingequipment such as laser lighting orlighting using huge reflector systems –will remain isolated cases and will not become part of general lighting practice.

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Play of brilliance

Focal glow.

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Basics2.0

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2.1 Perception2.1.1 Eye and camera2.1

Most of the information we receive aboutthe world around us is through our eyes.Light is not only an essential prerequisiteand the medium by which we are able to see. Through its intensity, the way it isdistributed throughout a space andthrough its properties, light creates specificconditions which can influence our perception.

Lighting design is, in fact, the planning ofour visual environment. Good lighting design aims to create perceptual con-ditions which allow us to work effectivelyand orient ourselves safely while pro-moting a feeling of well-being in a parti-cular environment and at the same timeenhancing that same enviroment in anaesthetic sense. The physical qualities ofa lighting situation can be calculated andmeasured. Ultimately it is the actual effect the lighting has on the user of a space, his subjective perception, thatdecides whether a lighting concept is suc-cessful or not. Lighting design can there-fore not be restricted to the creation of technical concepts only. Human per-ception must be a key consideration in thelighting design process.

2.1.1 Eye and camera

The process of perception is frequentlyexplained by comparing the eye with a camera. In the case of the camera, an adjustable system of lenses projects thereversed image of an object onto a light-sensitive film. The amount of light is controlled by a diaphragm. After developingthe film and reversing the image duringthe enlarging process a visible, two-dimensional image of the object becomesapparent.

Similarly, in the eye, a reversed imageis projected onto the inner surface of the eye, the so-called fundus oculi, via a deformable lens. The iris takes on the function of the diaphragm, the light-sensitive retina the role of the film. The image is then transported via the opticnerve from the retina to the brain, where it is adjusted in the cortex and madeavailable to the conscious mind.

Comparing the eye with the camera inthis way makes the process of vision fairlyeasy to understand, but it does not con-tribute to our comprehension of perception.The fault lies in the assumption that the image projected onto the retina isidentical to the perceived image. The factthat the retina image forms the basis forperception is undisputed, but there areconsiderable differences between what isactually perceived in our field of visionand the image on the retina.

Firstly, the image is spatially distortedthrough its projection onto the curvedsurface of the retina – a straight line is asa rule depicted as a curve on the retina.

Perception

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Spherical aberration.Projected images aredistorted due to thecurvature of the retina.

Chromatic aberration.Images are blurred due to the various degrees of refractionof spectral colours.

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2.1 Perception2.1.2 Perceptual psychology

This spherical misrepresentation is ac-companied by clear chromatic aberration– light of various wavelengths is refractedto varying degrees, which producescoloured rings around the objects viewed.

The eye is therefore a very inadequateoptical instrument. It produces a spatiallydistorted and non-colour corrected imageon the retina. But these defects are notevident in our actual perception of theworld around us. This means that theymust somehow be eliminated while theimage is being processed in the brain.

Apart from this corrective process thereare a number of other considerable diffe-rences between the image on the retinaand what we actually perceive. If we per-ceive objects that are arranged within aspace, this gives rise to images on the re-tina whose perspectives are distorted. A square perceived at an angle, for example,will produce a trapezoidal image on theretina. This image may, however, also havebeen produced by a trapezoidal surfaceviewed front on, or by an unlimited num-ber of square shapes arranged at anangle. The only thing that is perceived isone single shape – the square that thisimage has actually produced. This percep-tion of a square shape remains consistent,even if viewer or object move, although the shape of the image projected on theretina is constantly changing due to thechanging perspective. Perception cannottherefore only be purely a matter of rendering the image on the retina availableto our conscious mind. It is more a resultof the way the image is interpreted.

2.1.2 Perceptual psychology

Presenting a model of the eye to demon-strate the similarities to the workings of a camera does not provide any explanationas to how the perceived image comes intobeing – it only transports the object to be perceived from the outside world to thecortex. To truly understand what visualperception is all about, it is not so muchthe transport of visual information that isof significance, but rather the process involved in the interpretation of this infor-mation, the creation of visual impressions.

The next question that arises iswhether our ability to perceive the worldaround us is innate or the result of a lear-ning process, i.e. whether it has to be developed through experience. Anotherpoint to be considered is whether senseimpressions from outside alone are re-sponsible for the perceived image orwhether the brain translates these stimuliinto a perceivable image through the application of its own principles of order.

There is no clear answer to this que-stion. Perceptual psychology is divided onthis point. There are, in fact, a number ofcontradictory opinions, each of which canprovide evidence of various kinds to prove

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Perceptual constancy:perception of a shapein spite of the fact thatthe image on the retinais changing with thechanging perspective.

Perception of a shapebased on shadow for-mation alone whencontours are missing.

Recognising an overallshape by revealing essential details.

Matching a colour tothe respective pattern perceived. The colour ofthe central grey pointadjusts itself to theblack or white colour ofthe respective perceivedpattern of five

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their point. But not one of these schoolsof thought is able to give a plausible explanation for all the phenomena that occur during the visual process.

There is an indication that the spatialaspect of perception is innate. If youplace new-born animals (or six-month-old babies) on a glass panel that overlapsa step, they will avoid moving onto thearea beyond the step. This indicates thatthe innate visual recognition of depth and its inherent dangers have priorityover information relayed via the sense oftouch, which tells the animal, or baby,that they are on a safe, flat surface.

On the other hand, it can be demon-strated that perception is also dependenton previous experience. Known shapes are more easily recognised than unknownones. Once interpretations of complex visual shapes have been gained, they remain, and serve as a source of referencefor future perception.

In this case experience, and the ex-pectations linked with it, may be sostrong that missing elements of a shapeare perceived as complete or individualdetails amended to enable the object tomeet our expectations.

When it comes to perception, there-fore, both innate mechanisms and experi-ence have a part to play. It may be presumed that the innate component is responsible for organising or structuringthe information perceived,whereas on ahigher level of processing experience helpsus to interpret complex shapes and struc-tures.

As for the issue of whether impressionsreceived via the senses alone determineperception or whether the information also has to be structured on a psychicallevel, again there is evidence to proveboth these concepts. The fact that a greyarea will appear light grey if it is edged in black, or dark grey if it is edged inwhite can be explained by the fact that thestimuli perceived are processed directly –brightness is perceived as a result of the lightness contrast between thegrey area and the immediate surroundings.What we are considering here is a visual impression that is based ex-clusively on sensory input which is not in-fluenced by any criteria of order linkedwith our intellectual processing of thisinformation.

On the other hand, the fact that verticallines in a perspective drawing appear to be considerably larger furtherback in the drawing than in the fore-ground, can be explained by the fact thatthe drawing is interpreted spatially. A linethat is further away, i.e. in the back-ground, must be longer than a line in theforeground in order to produce an equi-valently large retina image – in the depthof the space a line of effectively the same length will therefore be interpretedand perceived as being longer.

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Constancy with regardto perception of size.Due to the perspectiveinterpretation of thisillustration the lumi-naires are all perceivedas being the same sizein spite of the variati-ons in size of the retinaimages.

In this case the per-spective interpretationleads to an optical illu-sion. The vertical lineto the rear appearsto be longer than aline of identical lengthin the foreground due to the perspective interpretation of thepicture.

The continuous lumi-nance gradient acrossthe surface of thewalls is interpreted asa property of thelighting of the wall.The wall reflectancefactor is assumed to beconstant. The grey ofthe sharply framedpicture is interpretedas a property of thematerial, although theluminance is identicalto the luminance ofthe corner of the room.

The perception of thelightness of the greysurface depends on itsimmediate surroundings.If the surrounding field is light an identicalshade of grey will appearto be darker than whenthe surrounding field is dark.

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Our apparent knowledge of distanceratios therefore gives rise to a change in the way we perceive things. As the distances in the drawing are however fic-titious, we can say that there is evidencethat the brain is able to perform inter-pretative processes that are not dependenton external stimuli. Perception thereforecannot be attributed to one principlealone, but results from various mecha-nisms.

2.1.2.1 Constancy

Even if there is not one simple explanationfor the way perception works, the questionregarding which objective the variousmechanisms serve remains an interestingone. Optical illusions provide an opportunityto examine the effects and aims of perception. Optical illusion is not a caseof a perceptual faux pas, but can be regarded as the border case of a mechanismthat provides essential information undereveryday conditions. This indicates thatboth phenomena described above, boththe changing perception of brightnesson identical surfaces and the erroneousperception of lines of equal length, can beexplained as stemming from one commonobjective.

One of the most important tasks of per-ception is to differentiate between constant objects and changes in our surroun-dings in the continuously changing shapes and distribution of brightness of the image on the retina. Since constantobjects also produce retina images ofvarying shapes, sizes and brightness arising due to changes in lighting, distanceor perspective, this indicates that mecha-nisms must exist to identify these objectsand their properties and to perceive themas being constant.

Our misinterpretation of lines of the samelength shows that the perceived size of an object does not depend on the size ofthe retina image alone, but that the dis-tance of the observer from the object is significant. Vice versa, objects of knownsizes are used to judge distances or to recognise the size of adjacent objects.Judging from daily experience this mechanism is sufficient to allow us to per-ceive objects and their size reliably. A per-son seen a long way away is therefore not perceived as a dwarf and a house on thehorizon not as a small box. Only inextreme situations does our perception deceive us: looking out of an aeroplane ob-jects on the ground appear to be tiny; theviewing of objects that are considerablyfarther away, e.g. the moon, is much moredifficult for us to handle.

Just as we have mechanisms that handlethe perception of size we have similarmechanisms that balance the perspective

distortion of objects. They guarantee thatthe changing trapezoidal and ellipsoidalforms in the retina image can be perceivedas spatial manifestations of constant, rectangular or round objects, while takinginto consideration the angle at which theobject is viewed.

When it comes to lighting designthere is a further complex of constancyphenomena that are of significance;those which control the perception ofbright-ness. Through the identification ofthe luminous reflectance of a surface it becomes apparent that a surface reflectslight differently depending on the inten-sity of the surrounding lighting, i.e. the luminance of a surface varies. The illumi-nated side of a unicoloured object has ahigher luminance than the side that receives no direct light; a black object insunlight shows a considerably higher levelof luminance than a white object in aninterior space. If perception depended onseen luminance, the luminous reflectancewould not be recognised as a constantproperty of an object.

A mechanism is required that deter-mines the luminous reflectance of a surface from the ratio of the luminances ofthis surface to its surroundings. This means that a white surface is assumed to bewhite both in light and shade, because in relation to the surrounding sufaces it reflects more light. There is, however, theborderline case, as indicated above, wheretwo surfaces of the same colour are per-ceived as being of a different brightnessunder the same lighting due to differentsurrounding surfaces.

The ability of the perceptual process torecognise the luminous reflectance of objects under different illuminance levelsis actually only half the story. There mustbe additional mechanisms that go beyondthe perception of luminous reflectance,while processing varying gradients andsharp differences in luminance.

We are familiar with changing luminancelevels on the surfaces around us. Theymay be the result of the type of lighting:one example of this is the gradualdecrease in brightness along the rear wallof a space that is daylit from one sideonly. Or they may arise from the spatialform of the illuminated object: examplesof this are the formation of typical shadows on spatial bodies such as cubes, cylinders or spheres. A third reason for the presence of different luminances may lie in the quality of the surface. Uneven reflectance results in uneven luminance even if the lighting is uniform.The aim of the perceptual process is to decide whether an object is of a singlecolour, but not lit uniformly, or whetherit is spatially formed or a uniformly lit object with an uneven reflection factor.

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The spatial impressionis determined by theunconscious assump-tion that light comesfrom above. By inver-ting the picture theperception of elevationand depth is changed.

The spatial quality ofan object can berecognised purely fromthe gradient of theshadows.

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2.1 Perception2.1.2 Perceptual psychology

The example shown here serves to explainthis process. As a rule the folded card isperceived as if it is being viewed from theoutside (fold to the front). In this case itappears to be uniformly white but lit fromone side. If the card is seen as being viewed from inside (fold to the rear), it isperceived as being uniformly lit but with one half coloured black. The luminancepattern of the retina image is thereforeinterpreted differently: in one case it is attributed to a characteristic black/whitecoloration of the perceived object; in theother case perception does not cover the different luminance in the perception of the apparently uniformly white card; it is taken to be a feature of the lighting situation.

One characteristic feature of perceptionis, therefore, the preference for simple and easily comprehensible interpretations.Differences in luminance are effectivelyeliminated from the perceived images to alarge extent or especially emphasized de-pending on whether they are interpretedas a characteristic feature of the object or as a feature of the surroundings – in thiscase, of the lighting.

These mechanisms should be taken intoconsideration when designing thelighting for a space. The first conclusionthat can be drawn is that the impressionof uniform brightness does not depend on totally uniform lighting, but that it can be achieved by means of luminancegradients that run uniformly.

On the other hand irregular or unevenluminances can lead to confusing lightingsituations. This is evident, for example,when luminous patterns created on thewalls bear no relation to the architecture.The observer’s attention is drawn to a luminance pattern that cannot be explainedthrough the properties of the wall, nor as an important feature of the lighting. If luminance patterns are irregular theyshould, therefore, always be in accordancewith the architecture.

The perception of colour, similar to theperception of brightness, is dependent onsurrounding colours and the quality of the lighting. The necessity to interpretcolours is based on the fact that colourappearances around us are constantlychanging.

A colour is therefore perceived asbeing constant both when viewed in thebluish light of an overcast sky or in warmerdirect sunlight – colour photographs taken under the same conditions, however,show the colour shifts we expect underthe particular lighting.

Perception is therefore able to adjust to the respective colour properties of thelighting, thereby providing constantcolour perception under changing condi-tions. This only applies, however, when

32

Change of perceptionfrom light/dark toblack/white if the spa-tial interpretation of the figure changes.

Light distribution thatis not aligned with thearchitectural structureof the space is perceived

as disturbing patternsthat do not relate tothe space.

The position of the luminous beam deter-mines whether it is perceived as back-ground or as a distur-bing shape.

The lighting distributionon an unstructuredwall becomes a dominant feature,whereas the samelighting distribution on a structured wall isinterpreted as back-ground and not per-ceived.

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2.1 Perception2.1.2 Perceptual psychology

the entire environment is lit with light ofthe same luminous colour and thelighting does not change too rapidly. If different lighting situations can be com-pared directly, the contrast due to differentluminous colours will be perceived. This becomes evident when the observermoves through spaces that are lit diffe-rently, but above all when different lightsources are used within one room or if the observer is in a space comprisingcoloured glazing and in a position to compare the lighting inside and outsidethe building. Lighting a space using different luminous colours can be doneeffectively, if the change of luminouscolour bears a clear relation to the re-spective environment.

2.1.2.2 Laws of gestalt

The main theme of this chapter so far hasbeen the question of how the properties ofobjects – size, form, reflectance andcolour – are perceived as being constantin spite of changing retina images. These considerations did not include howthe object itself is perceived.

Before properties can be attributed toan object, the object itself must be recog-nised, that is to say, distinguished from itssurroundings. The process of identifyingthis object in the profusion of continuouslychanging stimuli on the retina is no lessproblematic than the perception of objects. Or to put it in more general terms:how does the perceptual process definethe structures its attention has been drawnto and how does it distinguish them fromtheir surroundings.

An example will serve to illustrate thisprocess. In the drawing on the left mostpeople spontaneously see a white vaseagainst a grey background. On closer ex-amination two grey heads facing eachother against a white background becomeapparent. Once the hidden faces havebeen discovered, there is no difficulty inperceiving the vase or the faces, but it is impossible to see both at the same time.

In both cases we perceive a figure – eitherthe vase or the two faces against a back-ground of a contrasting colour. The sepa-ration of gestalt (form) and environment,of motif and background, is so completethat if you imagine that the form is moved, the background does not move inunison. In our example the background is therefore an area behind the form andfills the entire drawing. Apart from itscolour and its function as an environmentno other properties are attributed to thebackground area. It is not an object in itsown right and is not affected by changesinherent to the form. This impression isnot influenced by the knowledge that the"background" in our example, is in fact,another form, or gestalt – the perceptual

mechanism is stronger than our consciousreasoning.

This example shows that the complex andinconsistent patterns of the retina imageare ordered in the course of the perpetualprocess to enable us to interpret whatwe perceive easily and clearly. In our example, a portion of these patterns within one picture are grouped togetherto form an image, i.e. an object of interestwhile the rest of the patterns are regardedas the background and their properties by and large ignored.

Moreover, the fact that of the two in-terpretations the vase is the preferred oneshows that this process of interpretion is subject to certain rules; that is to say,that it is possible to formulate laws according to which certain arrangementsare grouped together to form shapes, i.e. objects of perception.

These rules are not only of value when itcomes to describing the perceptual pro-cess, they are also of practical interest forthe lighting designer. Every lighting installation comprises an arrangement of luminaires – on the ceiling, on the wallsor in the space. This arrangement is not perceived as such, but is organised intoforms or groups in accordance with thelaws of gestalt. The architectural settingand the lighting effects produced by the luminaires give rise to further patterns,which are included in our perception of the overall situation.

It might occur that these structuresare reorganised visually to such an extentthat we do not perceive the patterns as intended, but other shapes and forms.Another, negative effect may be – for example, in the case of a chessboard pat-tern – that gestalt and background cannot be clearly identified. The result is continuously shifting focus selection. It is therefore necessary to consider to the laws of gestalt when developinglighting design concepts.

33

Depending on how you view this drawing,you will see a vase ortwo heads facing eachother.

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2.1 Perception2.1.2 Perceptual psychology

An initial and essential principle of theperception of gestalt, is the tendency tointerpret closed forms as a figure.

Closed forms need not possess a continuouscontour. Elements arranged close together are grouped according to an-other law of gestalt, the law of proximity,and form a figure. The example on the left demonstrates that we first see a circleand then an arrangement of luminaires.The circles are arranged in such a strictorder that the imaginary linking lines between them is not straight, but forms a circle; the resulting shape is not a poly-gon but a perfect circle.

Apart from the effect produced by proxi-mity, there is another mechanism via which shapes that are not competely closed can be perceived as a gestalt. A closed shape is always seen as being onthe inside of the linking line – the forma-tive effect therefore only works in one direction. This inner side is usually identicalto the concave, surrounding side of the line that encloses the figure. This inturn leads to a formative effect even in the case of open curves or angles, rende-ring a figure visible inside the line, that is to say in the partly enclosed area. If thisleads to a plausible interpretation of the initial pattern, the effect of the inner sidecan be significant.

Patterns frequently possess no shapes thatcan be arranged according to the principles of closure or proximity, or theinner line. But in such cases there are laws of gestalt that allow certain arrange-ments to appear as a shape. The percep-tion of a form as a pure shape is based onsimple, logical structure, whereas morecomplex structures belonging to the samepattern disappear into an apparently con-tinuous background. One example of the this logical structuring of specific shapesis symmetry.

Shapes of equal width have a similar effect. This is not strictly a case of symmetry. A principle of order and orga-nisation is, however, evident, and thisallows us to perceive a shape.

If a pattern contains no symmetry or similar widths, uniform style can still beenough to render a shape a gestalt.

Apart from providing the ability to dis-tinguish shapes from their surroundings, i.e.figures from their background, perceptionalso clarifies the relation of figures to each other; be it the grouping together of individual shapes to form one large shapeor the inter-relationship of a number of shapes to form a group. The basic princi-ple that lies behind our ability to distin-guish between shapes and background isonce again evident here: our unconscioussearch for order in our visual field.

34

Law of gestalt relatingto proximity. Luminairesare grouped in pairs.

Law of gestalt relatingto proximity. Fourpoints are grouped toform a square, fromeight points upwards acircle is formed.

The downlights are ar-ranged in two lines in accordance with thelaw of pure form. Whentwo modular luminairesare added the arrange-ment is reorganisedaccording to the law ofsymmetry to form twogroups of five.

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2.1 Perception2.1.2 Perceptual psychology

A basic law of gestalt is to prefer to per-ceive lines as steady continuous curvesor straight lines, and to avoid bends anddeviations. The preferance to perceivecontinuous lines is so great that it can influence the overall interpretation of animage.

When it comes to two-dimensional shapesthe law of the continuous line conformswith the law of pure form. In this case,too, shapes are organised to create figuresthat are as simple and clearly arranged aspossible.

When a given number of individual shapesare put together to form groups, similarlaws of gestalt come into play as with thefocal selection of figure and background.The proximity of shapes is an equally essential principle in this regard.

A further criterion for the formulation ofgroups is symmetry. Especially in the caseof axial symmetry (arrangements arounda vertical axis) the mirrored shapes are always grouped in pairs. This effect can beso strong that the grouping of adjacentshapes according to the law of proximitybecomes irrelevant.

Besides spatial layout, the structure of theshapes themselves is also responsible forthe formation into groups. The shapes inthe adjacent drawing are not organisedaccording to proximity or axial symmetry,but in groups of identical shapes. Thisprinciple of identity also applies when theshapes in a group are not absolutely iden-tical but only similar.

The final law of gestalt for the arrangementof groups is a special case, as it involvesthe element of movement. In the case ofthe law of "common destiny" it is not the similarity of structure, but rathera mutual change, predominantly of thespatial position, which assembles the figures into groups. This becomes apparentwhen some of the forms that were originally attributed to a previously well-organised group, move in unison, becausein contrast to the remaining figures, it is as if they are drawn on a transparentoverlay, which is placed on the originalpattern. The common movement of the group in contrast to the immovabilityof the other figures renders their belongingtogether in any purposeful sense so probable that the original image is sponta-neously reinterpreted.

At first glance these laws of gestalt appear to be very abstract and of littlesignificance for the lighting designer. But these laws of gestalt do play an important role in the development of luminaire arrangements. The actuallighting effect produced by a planned arrangement of luminaires may deviatetotally from the original design, if the concept it is based on ignores themechanisms inherent to perception.

35

Law of gestalt relatingto continuous lines.The arrangement is interpreted as two linescrossing.

Law of gestalt relatingto pure form. The arran-gement is interpreted astwo superimposed rec-tangles.

Law of gestalt relatingto similarity. Luminairesof the same type are grouped together.

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Choroid membrane forblood supply to the eye

Retina, location of thelight-sensitive receptors

Sclera

Fovea

Optical nerve

Cornea

Cavity

Lens

Vitreous body

Iris with pupil as thevisual aperture

Ciliary muscle foradaptation of lens todifferent viewingdistances (accommo-dation)

2.1 Perception2.1.3 Physiology of the eye

36

Sectional view of theeye, representationshowing the parts ofthe eye which are sig-nificant in the physio-logy of vision:

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1,0

0,8

0,6

0,4

0,2

400 500 600 700 ¬ (nm)800

VV'

60˚ 40˚ 20˚ 0˚ 20˚ 40˚ 60˚

Blind spotConesRods

temporal nasal16 .104

N

8.104

12 .104

4.104

2.1 Perception2.1.3 Physiology of the eye

2.1.3 Physiology of the eye

The information presented in this chapteris based on the consideration that it is inadequate to portray the eye as an opticalsystem when describing human perception.The process of perception is not a matter of how an image of our environment is transferred to the retina, but how theimage is interpreted, how we differentiatebetween objects with constant properties in a changing environment. Although this means that priority will be given here to the process by which the image is createdboth physiologically and psychologically,the eye and its fundamental propertiesshould not be ignored.

The eye is first and foremost an optical system creating images on the retina. We have described this system by comparingthe eye with a camera, but more interestingby far is the surface on which the imageoccurs - the retina. It is in this layer that the pattern of luminances is translatedinto nervous impulses. The retina has,therefore, to possess light sensitive receptors that are numerously sufficientto allow a high resolution of the visualimage.

On close examination it is evident that thesereceptors are not arranged in a uniformpattern; the retina is a very complicatedstructure: firstly there are two differenttypes of receptor, the rods and the cones,which are not distributed evenly over the retina. At one point, the so-called“blind spot”, there are no receptors at all, as this is the junction between the opticnerves and the retina. On the other hand there is an area called the fovea, which is at the focal point of the lens.Here there is the greatest concentrationof cones, whereas the density of the cones reduces rapidly towards the peripheralarea. This is where we find the greatestconcentration of rods, which are not evidentat all in the fovea.

The reason for this arrangement of differentreceptor types lies in the fact thatour eyes consist of two visual systems. Theolder of these two systems, from anevolutionary point of view, is the one in-volving the rods. The special features of thissystem are a high level of light-sensitivityand a large capacity for perceiving movement over the entire field of vision.On the other hand, rods do not allow us to perceive colour; contours are not sharp,and it is not possible to concentrate on objects, i.e. to study items clearlywhen they are in the centre of our field ofvision.

The rod system is extremely sensitiveand it is activated when the illumance level is below 1 lux. The main features of night vision - mainly the fact that colouris not evident, contours are blurred and poorly lit items in our peripheral field

of vision are more visible – can be explainedby the properties of the rod system.

The other type of receptors, the cones, makeup a system with very different properties.This is a system which we require to seethings under greater luminous intensities,i.e. under daylight or electric light. The cone system has a lower level of light-sensitivity and is concentrated in the central area around the fovea. It allows us to see colours and sharper contours of objects on which we focus, i.e. whoseimage falls in the fovea area.

In contrast to rod vision, we do notperceive the entire field of vision uniformly;the main area of perception is in the central area. The peripheral field of visionis also significant, however; if interestingphenomena are perceived in that area then our attention is automatically drawnto these points, which are then received as an image in the fovea to be examinedmore closely. Apart from noticing suddenmovement, striking colours and patterns,the main reason for us to change our direction of view is the presence ofhigh luminances - our eyes and attentionare attracted by bright light.

One of the most remarkable properties of the eye is its ability to adapt to differentlighting conditions. We can perceive the world around us by moonlight or sun-light, although there is a difference of a factor of 105 in the illuminance. Theextent of tasks the eye is capable of performing is extremely wide - a faintlyglowing star in the night’s sky can be perceived, although it only produces anilluminance of 10-12 lux on the eye.

This accomodation is only influenced toa very small extent by the pupil, which regulates incident light in a 1:16 ratio.Adaptation is performed to a large extentby the retina. The rod and cone systemhandles different levels of light intensity.The rod system comes into effect in relation to night vision (scotopic vision),the cones allow us to see during the day-time (photopic vision) and both receptorsystems are activated in the transitiontimes of dawn and dusk (mesopic vision).

Although vision is therefore possibleover an extremely wide area of luminancesthere are clearly strict limits with regard to contrast perception in each individuallighting situation. The reason for this lies in the fact that the eye cannot coverthe entire range of possible luminances at one and the same time, but adapts tocover one narrow range in which differentiated perception is possible. Objects that possess too high a luminancefor a particular level of adaptation causeglare, that is to say, they appear to be extremely bright. Objects of low luminance,on the other hand, appear to be too dark.

The eye is able to adjust to new luminance conditions, but as it does so it

37

Number N of rods andcones on the retina inrelation to the angle ofsight.

Relative spectral lumi-nous efficiency of rodsV’ and cones V.

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1,70 m

0˚10˚

20˚45˚

3

2

45˚1

65˚1

30˚

15˚

2

3

15˚

30˚

65˚

1,20 m

15˚ 25˚ 40˚

90˚

1.0

0.6

0.2

15˚ 25˚ 40˚å

H

1,20 m

30˚1

0˚2

25˚

35˚

360˚

2.1 Perception2.1.4 Objects of perception

simply selects a different but restrictedrange. This process of adaptation doestake time. Adapting from dark to light situations occurs relatively rapidly, whereasadapting from light to darkness requires a considerably longer time. A good exampleof this is how bright we find it outsidehaving come out of a dark cinema audi-torium during the daytime, or the transitoryperiod of night blindness we experiencewhen entering a very dark room. Both the fact that contrast in luminance can onlybe processed by the eye within a certainrange, plus the fact that it takes time to adapt to a new level of lighting, or brightness, have an impact on lightingdesign: the purposeful planning of different luminance grades within a space,for example, or when adjusting lightinglevels in adjacent spaces.

2.1.4 Objects of perception

Although this chapter has described thepsychological mechanisms involved in the perception process together with thephysiological prerequisites, a third areahas only been touched upon - the subjectof perception. To this point the things that were seen were either “objects”or “figures” in general or examples chosento illustrate a certain mechanism. We donot perceive any object that comes withinour field of vision, however. The way thefovea prefers to focus on small, changingscenes shows that the perception processpurposefully selects specific areas. This selection is inevitable, as the brain isnot capable of processing all the visualinformation in the field of vision, and it alsomakes sense because not all the informationthat exists in our environment is necessarilyrelevant for perception.

Any attempt to describe visual perceptioneffectively must therefore also take intoaccount the criteria by which the selectionof the perceived information is effected. In the first instance the value of anyparticular information relates to the cur-rent activity of the observer. This activitymay be work or movement-related or anyother activity for which visual informationis required.

The specific information received de-pends on the type of activity. A cardriver has to concentrate on different visualtasks than a pedestrian. A precision mechanic processes different informationthan a worker in a warehouse. A visualtask can be defined by size or location; it is of importance whether a visual task ismovement-related or not, whether smalldetails or slight contrasts have to be regi-stered, whether colours or surface structures are essential properties. Lightingconditions under which the visual task can be perceived to an optimum degree can be determined from the above-mentioned specific features. It is possible

38

Visual field (1), prefer-red visual field (2) andoptimum field of vision(3) of a person standing(above) and sitting(centre, below) for vertical visual tasks.

Frequency H of angleof sight å for horizon-tal visual tasks. Prefer-red field of vision be-tween 15° and 40°,preferred direction ofview 25°.

Preferred field of visionfor horizontal visualtasks. Preferred directionof view 25°.

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10 210 010-210-410-610-8 10 4 10 6 10 87 L (cd/m2)

5

4

3

2

1

6

2.1 Perception2.1.4 Objects of perception

to define ways of lighting which will opti-mise the performace of specific activities.Investigations have been carried out especially in office and traffic situationsto study the respective visual tasks and a wide range of activities and to determinethe conditions required for optimum per-ception. Standards and recommendationsfor the lighting of workplaces and trafficsystems are based on the findings of thisresearch.

There is, however, another basic needfor visual information that goes beyondthe specific information required for a particular activity. This requirement forinformation is not related to any particu-lar situation, it is the result of man’s biological need to understand the world around him. Whereas you can enable a person to work more effectively by crea-ting optimum perceptual conditions for certain activities, man’s feeling of well-being in his visual environment depends on satisfying his biological need for infor-mation.

Much of the information required results from man’s need to feel safe. To beable to evaluate a danger you haveto be able to comprehend the structure of your environment. This applies both to orientation – knowing where you are,which route you are on, and what the potential destinations may be – and know-ledge about the qualities and peculiaritiesof the environment you find yourself in.This knowledge, or lack of information, de-termines the way we feel and our behaviour.It can lead to a feeling of tension and un-rest in unknown or potentially dangeroussituations, or relaxation and tranquility in a familiar and safe environment. Otherinformation about the world around us is required to allow us to adapt our beha-viour to the specific situation. This may include knowledge of weather conditionsand the time of day as well as informa-tion relating to other activities occurringin the given environment. Should this information not be available, e.g. in large,windowless buildings, the situation isoften interpreted as being unnatural andoppressive.

A third area arises from man’s socialneeds. The need for contact with otherpeople and the demand for a private sphereare somewhat contradictory and have to be carefully balanced. The focus on whichvisual information is to be taken inis, therefore, determined by the activitiesbeing performed in a given environmentand man’s basic biological needs. Areasthat promise significant information – be it in their own right, or through accentuation with the aid of light – areperceived first. They attract our attention.The information content of a given objectis responsible for its being selected as an object of perception. Moreover, the infor-mation content also has an influence on the way in which an object is perceivedand evaluated.

The glare phenomenon illustrates thisparticularly well. If the exterior lighting is especially strong, an opal glass windowwill produce glare, a fact that can be explained physiologically by the greatcontrast between the luminance of the window and the considerably lower luminance level of the surrounding wallsurface. In the case of a window that provides an interesting view outside, the contrast is greater, but the feeling thatwe are being subjected to disturbing glaredoes not arise. Glare can, therefore, not only be explained from a physiologicalstandpoint, as it occurs when a bright surface with no information content attracts our attention. Even high luminancecontrasts are felt to be glare-free, if the area perceived offers interesting infor-mation. It is therefore clear that it is not practical to stipulate photometricquantities – e.g. luminance or illuminancelimits – out of context, since the actualperception of these photometric quantitiesis influenced by the processing of the infor-mation provided.

39

Luminance range L ofrod vision (1), mesopicvision (2) and cone vision (3). Luminances(4) and preferred lumi-nances (5) in interiorspaces. Absolute thres-hold of vision (6) andthreshold of absoluteglare (7).

Typical illuminances Eand luminances underdaylight and electriclight.

E (lux)Sunlight 100 000Overcast sky 10 000Task lighting 1000Circulation zone lighting 100Street lighting 10Moonlight 1

L (cd/m2)Sunlight 1000 000 000Incandescent lamp (matt finish) 100 000Fluorescent lamp 10 000Sunlit Clouds 10 000Blue sky 5 000Luminous ceiling 500Louvred luminaires 100Preferred values in interior spaces 50–500White paper at 500 lx 100Monitor (negative) 10–50White paper at 5 lx 1

Page 40: ERCO HANDBOOK

[Ï] = Lumen (lm)

æ = ÏP

I = ÏØ

[æ] = ImW

[I] = Imsr

= Candela (cd)Imsr

Q = Ï . t[Q] = Im . h

Ï

Ï ØI

2.2 Terms and units

In lighting technology a number of technicalterms and units are used to describe theproperties of light sources and the effectsthat are produced.

2.2.1 Luminous flux

Luminous flux describes the total amountof light emitted by a light source. This radiation could basically be measured or expressed in watt. This does not, however,describe the optical effect of a light sourceadequately, since the varying spectralsensitivity of the eye is not taken into account.

To include the spectral sensitivity ofthe eye the luminous flux is measured in lumen. Radiant flux of 1 W emitted at thepeak of the spectral sensitivity (in thephotopic range at 555nm) produces a luminous flux of 683lm. Due to the shapeof the V (l) curve the same radiant fluxwill produce correspondingly less luminousflux at different frequency points.

2.2.2 Luminous efficacy

Luminous efficacy describes the luminousflux of a lamp in relation to its powerconsumption and is therefore expressedin lumen per watt (lm/W). The maximumvalue theoretically attainable when the total radiant power is transformed intovisible light is 683 lm/W. Luminous efficacy varies from light source to lightsource, but always remains well below thisoptimum value.

2.2.3 Quantity of light

The quantity of light, or luminous energy(US), is a product of the luminous flux emitted multiplied by time; luminousenergy is generally expressed in klm ·h.

2.2.4 Luminous intensity

An ideal point-source lamp radiates lumi-nous flux uniformly into the space inall directions; its luminous intensity is thesame in all directions. In practice, how-ever, luminous flux is not distributed uni-formly. This results partly from the designof the light source, and partly on the way the light is intentionally directed. It makes sense, therefore, to have a wayof presenting the spatial distribution of luminous flux, i.e. the luminous intensitydistribution of the light source.

The unit for measuring luminous in-tensity is candela (cd). The candela is the primary basic unit in lighting technologyfrom which all others are derived. The candela was originally defined by the luminous intensity of a standardised candle.Later thorium powder at the temperatureof the solidification of platinum was de-

40

2.2

Terms and units

The amount of lightemitted by a lightsource is the luminousfluxÏ.

Luminous intensity I is the luminous flux Ï radiating in a given direction per solid angle Ø.

Page 41: ERCO HANDBOOK

[I] = cd[I'] = cd/kIm[Ï] = kIm

I = I' . Ï

C 90/270˚

C 0/180˚

C 0/180˚

C 90/270˚

-40˚ -20˚ 0˚ 20˚ 40˚

I'2

I'

G

å åß©

0˚ 30˚

60˚

90˚

-30˚

-60˚

-90˚

I'

I'2

G

å

ß

©

0˚I

90˚

90˚

I

2.2 Terms and units

fined as the standard; since 1979 the candelahas been defined by a source of radiationthat radiates 1/683 W per steradian at afrequency of 540 ·1012 Hz.

The distribution of the luminous in-tensity of a light source throughout a space produces a three-dimensional graph.A section through this graph results in a luminous intensity distribution curve,which describes the luminous intensity onone plane. The lumious intensity is usuallyindicated in a polar coordinate system asthe function of the beam angle. To allowcomparison between different light sourcesto be made, the light distribution curvesare based on an output of 1000 lm. In thecase of symmetrical luminairesone lightdistribution curve is sufficient to describeone luminaire, axially symmetrical luminaires require two curves, which areusually depicted in one diagram. The polar coordinate diagram is not sufficientlyaccurate for narrow-beam luminaires, e.g. stage projectors. In this case it is usualto provide a Cartesian coordinate system.

41

Luminous intensitydistribution body anddiagram (for planes C0/180° and C 90/270°)of an axially symmetri-cal luminaire.

Luminous intensitydistribution of a lightsource having rotationalsymmetry. A sectionthrough the C planeproduces the luminousintensity distributioncurve.

Conversion of 1000lm-related luminousintensity I’ to effectiveluminous intensity l.

Luminous intensitydistribution curvestandardised to 1000lm, represented in polar coordinates andCartesian coordinates.The angle within whichthe maximum luminousintensity l' is reducedto l'/2, identifies thebeam spread !. The cut-off angle å is the limiting angle of theluminous intensity dis-tribution curve.

Page 42: ERCO HANDBOOK

EÏ A

Eh Ev

Ï

Em

A

I

Ep

a

L

I Ap

Eh Ev

®1

®2

L1

L2

2.2 Terms and units

2.2.5 Illuminance

Illuminance is the means of evaluating thedensity of luminous flux. It indicates the amount of luminous flux from a lightsource falling on a given area. Illuminanceneed not necessarily be related to a realsurface. It can be measured at any pointwithin a space. Illuminance can be deter-mined from the luminous intensity of thelight source. Illuminance decreases withthe square of the distance from the lightsource (inverse square law).

2.2.6 Exposure

Exposure is described as the product of theilluminance and the exposure time.Exposure is an important issue, for example,regarding the calculating of light exposureon exhibits in museums.

2.2.7 Luminance

Whereas illuminance indicates the amountof luminous flux falling on a given surface,luminance describes the brightness of an illuminated or luminous surface. Luminanceis defined as the ratio of luminous intensityof a surface (cd) to the projected area ofthis surface (m2).

In the case of illumination the light canbe reflected by the surface or transmittedthrough the surface. In the case of diffusereflecting (matt) and diffuse transmitting(opaque) materials luminance can be calculated from the illuminance and thereflectance or transmittance.

Luminance is the basis for describingperceived brightness; the actual brightnessis, however, still influenced by the state of adaptation of the eye, the surroundingcontrast ratios and the information contentof the perceived surface.

42

Illuminance E indicatesthe amount of lumi-nous flux from a lightsource falling ona given surface A.

Horizontal illuminanceEh and vertical illumin-nance Ev in interiorspaces.

Average illuminance Emis calculated from theluminous flux Ï fallingon the given surface A.

The luminance of a lu-minous surface is the ratio of luminousintensity l and the pro-jected surface area Ap.

The illuminance at a point Ep is calculatedfrom the luminous intensity l and the dis-tance a between the light source andthe given point.

The luminance of an illuminated surfacewith diffuse reflectanceis proportional to the illuminance andthe reflectance of thesurface.

Em = ÏA

Ep = Ia2

L = IAp

L1 = Eh . ®1¿

L2 = Ev . ®2¿

[L] = cdm2

[L] = cdm2

[Ep] = Ix

[I] = cd

[a] = m

[E] = Ix

Page 43: ERCO HANDBOOK

1,0

0,8

0,6

0,4

0,2

500 1000 1500 2000 2500¬ (nm)

Se (%)

10 16

10 14

10 12

10 10

10

10

10

10

10 0

10

10

10 6-

4-

2-

2

4

6

8

Medium wave

Cosmic radiation

Long wave

Audiofrequencies

Short waveUltra short wave

MicrowavesRadar

IR radiation

Centimetre wavesDecimetre waves

UV radiationX rays

Gamma rays

¬ (nm) ¬ (nm)

300

350

400

450

500

550

600

650

700

750

800

850

IR radiation

UV radiation

2.3 Light and light sources2.3

Light, the basis for all vision, is an elementof our lives that we take for granted. We are so familiar with brightness, darknessand the spectrum of visible colours thatanother form of perception in a differentfrequency range and with different coloursensitivity is difficult for us to imagine.Visible light is in fact just a small part of anessentially broader spectrum of electro-magnetic waves, which range from cosmicrays to radio waves.

It is not just by chance that the 380 to780 nm range forms the basis for our vision, i.e. “visible light”. It is this very rangethat we have at our disposal as solar radiation on earth in relatively uniformamounts and can therefore serve as a re-liable basis for our perception.

The human eye therefore utilises thepart of the spectrum of electromagneticwaves available to gather information about the world around us. It perceives theamount and distribution of the light thatis radiated or reflected from objects to gain information about their existence or their quality; it also perceives the colourof this light to acquire additional infor-mation about these objects.

The human eye is adjusted to the only lightsource that has been available for millionsof years – the sun. The eye is therefore at its most sensitive in the area in which we experience maximum solar radiation.Our perception of colour is therefore also attuned to the continuous spectrumof sunlight.

The first artificial light source was the flameof fire, in which glowing particles of carbon produce light that, like sunlight, hasa continuous spectrum. For a long timethe production of light was based on thisprinciple, which exploited flaming torchesand kindling, then the candle and the oil lamp and gas light to an increasinglyeffective degree.

With the development of the incan-descent mantle for gas lighting in the second half of the 19th century the principleof the self luminous flame became outdated; in its place we find a material thatcan be made to glow by heating – the flame was now only needed to producethe required temperature. Incandescent gas light was accompanied practically simultaneously by the development ofelectric arc and incandescent lamps,which were joined at the end of the 19thcentury by discharge lamps.

In the 1930s gas light had practically beencompletely replaced by a whole range of electric light sources,whose operationprovides the bases for all modern lightsources. Electric light sources can be dividedinto two main groups, which differ according to the processes applied to convertelectrical energy into light. One groupcomprises the thermal radiators, they includeincandescent lamps and halogen lamps.The second group comprises the dischargelamps; they include a wide range of lightsources, e.g. all forms of fluorescent lamps,mercury or sodium discharge lamps andmetal halide lamps.

43

Light and lightsources

Relative spectral dis-tribution Se (l) of solarradiation (sunlight and sky light) with a pronounced emission maximum in the visiblerange.

Ranges of electromag-netic radiation. Thespectrum of visible ra-diation comprises thenarrow band between380 and 780 nm.

Page 44: ERCO HANDBOOK

Incandescent lamps Halogen lamps

Low-voltagehalogen lamps

Fluorescent lamps Mercury lamps

Compactfluorescent lamps

Metal halide lamps

Low-pressuresodium lamps

High-pressuresodium lamps

High-pressure lampsLow-pressure lamps

Discharge lampsThermal radiators

Technical lamps

2.3 Light and light sources

44

Representation of thedifferent kinds of electric light sourcesaccording to the means of their lightproduction. In the caseof technical lamps the main distinction is between thermal radiators and dischargelamps. Discharge lampsare further subdividedinto high-pressure and

low-pressure lamps.Current developmentsshow a marked trendtowards the develop-ment of compact lightsources such as low-voltage halogen lamps,compact fluorescentlamps and metal halidelamps.

Page 45: ERCO HANDBOOK

100

80

60

40

20

400 1000600 800

Se (%)

¬ (mm)1200 1400

max

3500 K

4000 K

3000 K2500 K

¬��

100

80

60

40

20

20 40 60 80 100(%)U/Un

Ï (%) 2800 K

2700 K

2600 K

2500 K2400 K

2300 K2200 K

2100 K2000 K

2.3 Light and light sources2.3.1 Incandescent lamps

2.3.1 Incandescent lamps

The incandescent lamp is a thermal radiator.The filament wire begins to glow when it is heated to a sufficiently hightemperature by an electric current. As thetemperature increases the spectrum of the radiated light shifts towardsthe shorter wavelength range – the red heatof the filament shifts to the warm whitelight of the incandescent lamp. Dependingon lamp type and wattage the tem-perature of the filament can reach up to3000 K, in the case of halogen lamps over3000 K. Maximum radiation at these temperatures still lies in the infrared range,with the result that in comparison to the visible spectrum there is a high degree ofthermal radiation and very little UV radia-tion. Lack of a suitable material for the filament means that it is not possible toincrease the temperature further, whichwould increase the luminous efficacy andproduce a cool white luminous colour. As is the case with all heated solid bodies– or the highly compressed gas producedby the sun – the incandescent lamp radiates a continuous spectrum. The spectraldistrbution curve is therefore continuousand does not consist of a set of individuallines. The heating of the filament wire results from its high electrical resistance –electrical energy is converted into radiantenergy, of which one part is visible light.Although this is basically a simple principle,there are a substantial number of practicalproblems involved in the construction of an incandescent lamp. There are only afew conducting materials, for example,that have a sufficiently high melting pointand at the same time a sufficiently lowevaporation rate below melting point thatrender them suitable for use as filamentwires.

Nowadays practically only tungsten is usedfor the manufacture of filament wires,because it only melts at a temperature of3653 K and has a low evaporation rate.The tungsten is made into fine wires andis wound to make single or double coiledfilaments.

In the case of the incandescent lamp thefilament is located inside a soft glass bulb, which is relatively large in order to keep light loss, due to deposits of evapo-rated tungsten (blackening), to a minimum.To prevent the filament from oxidisingthe outer envelope is evacuated for low wattages and filled with nitrogen or a nitrogen-based inert gas mixture for higher wattages. The thermal insulationproperties of the gas used to fill the bulbincreases the temperature of the wire filament, but at the same time reducesthe evaporation rate of the tungsten,which in turn leads to increased luminousefficacy and a longer lamp life. The inertgases predominantly used are argonand krypton. The krypton permits a higheroperating temperature – and greater lu-

45

Incandescent lampswith tungsten filamentsin an evacuated or gas-filled glass bulb. General service lamp(left) and pressed-glasslamp with integratedparabolic reflector(right).

Spectral distribution Se (¬) of a thermal radiator at different filament temperatures. As the temperature increases the maximumradiation shifts intothe visible range.

Dimming characteristicsof incandescent lamps.Relative luminous flux Ïand colour temperatureas a function of the relative voltage U/Un. A reduction in voltageresults in a dispro-portionate decrease inluminous flux.

Page 46: ERCO HANDBOOK

2.3 Light and light sources2.3.1 Incandescent lamps

46

General service lamp:the principle of produ-cing light by means of an electrically heatedwire filament has been known since1802. The first functional incandescent lampswere made in 1854 byHeinrich Goebel.

The real breakthroughthat made the incan-descent the most com-mon light source canbe ascribed to ThomasAlva Edison, who deve-loped the incandescentlamp as we know it today in 1879.

The inside of the lampis either evacuated or filled with inert gas

Filament, usually adouble coil of tungstenwire

Clear, matt or colouredglass bulb. Parts of theglass bulb can be provi-ded with a silver coatingto form a reflector

Insulated contact forconnection to the phase

Screw cap to securelamp mechanically, alsoserves as a contact to the neutral conductor

Connection wires withintegrated fuse

Glass stem, with insula-ted filament supports

Page 47: ERCO HANDBOOK

100

80

60

40

20

20 40 60 80 100(%)U/Un

P (%)

180

140

100

60

20

80 90 100 110 120

%

(%)U/Un

P

t Ï

æ

100

80

60

40

20

600 1000 1400t (h)

200 1800

ÏA (%)

100

80

60

40

20

t (h)600200 1000 1400 1800

Ï (%)

100

80

60

40

20

t (h)

N (%)

600 1000 1400200 1800

2.3 Light and light sources2.3.1 Incandescent lamps

minous efficacy. Due to the fact that it isso expensive, krypton is only used in specialapplications.

A characteristic feature of incandescentlamps is their low colour temperature -the light they produce is warm in compa-rison to daylight. The continuous colourspectrum of the incandescent lamp providesexcellent colour rendition.

As a point source with a high lumi-nance, sparkling effects can beproduced on shiny surfaces and the light easily controlled using optical equipment. Incandescent lamps can therefore be applied for both narrow-beam accentlighting and for wide-beam generallighting.

Incandescent lamps can be easily dim-med. No additional control gear is re-quired for their operation and the lamps canbe operated in any burning position. In spite of these advantages, there are a number of disadvantages: low luminousefficacy, for example, and a relativelyshort lamp life, while the lamp life relatessignificantly to the operating voltage.Special incandescent lamps are availablewith a dichroic coating inside the bulbthat reflects the infrared component backto the wire filament, which increases theluminous efficacy by up to 40 %.

General service lamps (A lamps) are availa-ble in a variety of shapes and sizes. Theglass bulbs are clear, matt or opal. Specialforms are available for critical applica-tions (e.g. rooms subject to the danger of explosion, or lamps exposed to mechani-cal loads), as well as a wide range of special models available for decorativepurposes.

A second basic model is the reflectorlamp (R lamp). The bulbs of these lamps are also blown from soft glass, although,in contrast with the A lamps, which radiate light in all directions, the R lampscontrol the light via their form and a partly silvered area inside the lamp. An-other range of incandescents are the PAR(parabolic reflector) lamps. The PARlamp is made of pressed glass to provide a higher resistance to changes in tempera-ture and a more exact form; the parabolicreflector produces a well-defined beamspread.

In the case of cool-beam lamps, a subgroup of the PAR lamps, a dichroic, i.e. selectively reflective coating, is applied. Dichroic reflectors reflect visiblelight, but allow a large part of the IR radiation to pass the reflector. The thermalload on illuminated objects can thereforebe reduced by half.

47

Proportion of operatinglamps N, lamp lumens Ïand luminous flux of total installation ÏA(as the product of bothvalues) as a function of the operating time t.

Exponential correlationbetween the relativevoltage U/Un and elec-trical and photometricquantities.

Relative power P of incandescent lamps asa function of voltage.

Effect of overvoltageand undervoltage on relative luminous flux Ï,luminous efficacy n, electrical power P andlamp life t.

Luminous flux = ( )3.8UUn

ÏÏn

Luminous efficacy = ( )2.3UUn

ææn

Power = ( )1.5UUn

PPn

Lamp life = ( )–14UUn

ttn

Colour temperature = ( )0.4UUn

TfTfn

Page 48: ERCO HANDBOOK

2.3 Light and light sources2.3.1 Incandescent lamps

48

Top row (from left toright): decorative lamp,general service lamp,reflector lamp with softglass bulb and ellipsoi-dal or parabolic reflec-tor, producing mediumbeam characteristics. Bottom row (from leftto right): reflector lampwith pressed glass bulb and efficient para-bolic reflector (PAR lamp),available for narrow-beam (spot) and wide-beam (flood), also suitable for exterior application due to its high resistance to changes in tempera-ture; high-power pressed-glass reflectorlamp.

PAR lamp with dichroiccool-beam reflector. Visible light is reflected,infrared radiationtransmitted, thereby reducing the thermalload on the illuminatedobjects.

Incandescent lamp with glass bulb coated with dichroic material(hot mirror). This allows visible light to be transmitted; infraredradiation is reflectedback to the filament.The increase in the temperature of the filament results in increased luminous efficacy.

Page 49: ERCO HANDBOOK

180

140

100

60

20

80 90 100 110 120

%

(%)U/Un

P

t Ï

æ

100

80

60

40

20

1000 2000 3000t (h)

N (%)

2.3 Light and light sources2.3.1 Incandescent lamps

49

2.3.1.1 Halogen lamps

It is not so much the melting point of thetungsten (which, at 3653 K, is still a rela-tively long way from the approx. 2800 Kof the operating temperature of incan-descents) that hinders the construction ofmore efficient incandescent lamps, butrather the increasing rate of evaporationof the filament that accompanies the increase in temperature. This initially leadsto lower performance due to the blackeningof the surrounding glass bulb until finally the filament burns through. The price to be paid for an increase in luminous efficiency is therefore a shorterlamp life.

One technical way of preventing the blackening of the glass is the adding ofhalogens to the gas mixture inside thelamp. The evaporated tungsten combineswith the halogen to form a metal halide,which takes on the form of a gas at the temperature in the outer section of thelamp and can therefore leave no depositson the glass bulb. The metal halide is splitinto tungsten and halogen once again at the considerably hotter filament and thetungsten is then returned to the coil.

The temperature of the outer glassenvelope has to be over 250° C to allow thedevelopment of the halogen cycle to take place. In order to achieve this a com-pact bulb of quartz glass is fitted tightlyover the filament. This compact form not only means an increase in temperature,but also an increase in gas pressure,which in turn reduces the evaporation rateof the tungsten.

Compared with the conventional incan-descent the halogen lamp gives a whiterlight – a result of its higher operatingtemperature of 3000 to 3300 K; its lumi-nous colour is still in the warm whiterange. The continuous spectrum producesexcellent colour rendering properties. Thecompact form of the halogen lamp makesit ideal as a point-source lamp; its light canbe handled easily and it can create attractive sparkling effects. The luminousefficacy of halogen lamps is well abovethat of conventional incandescents –especially in the low-voltage range.Halogen lamps may have a dichroic, heat-reflecting coating inside the bulbs, whichincreases the luminous efficacy of theselamps considerably.

The lamp life of halogen lamps is longer than that of conventional incandes-cents. Halogen lamps are dimmable.Like conventional incandescent lamps, theyrequire no additional control gear; low-voltage halogen lamps do have to be runon a transformer, however. In the case of double-ended lamps, projector lamps andspecial purpose lamps for studios the burning position is frequently restricted.Some tungsten halogen lamps have to beoperated with a protective glass cover.

Influence of overvol-tage and undervoltageon relative luminousflux Ï, luminous effi-cacy n, electrical powerP and lamp life t.

Proportion of operatinglamps N as a function of the operating time t.

Halogen cycle: combi-nation of evaporatedtungsten and halogento produce tungstenhalide in the peripheralarea. Splitting of thetungsten halogens backto the filament.

Halogen lamp for mainsvoltage with screw capand outer envelope(left). The outer envelopemeans that the lampcan be operated with-out a protective glasscovering. Low-voltagehalogen lamp with pinbase and axial filamentin a quartz glass bulb(right).

Page 50: ERCO HANDBOOK

Like almost all conventional incandescentlamps, halogen lamps can be run onmains voltage. They usually have specialcaps, but some are equipped with an E 27screw cap and an additional glass envelopeand can be used in the same way as conventional incandescents.

As well as mains voltage halogen lamps,low-voltage halogen lamps are also gaining in importance. The advantages of this latter light source – high luminous efficiency in a small-dimensioned lamp –resulted in wide application of low-voltagehalogen lamps in the field of architecturallighting.

The lamp’s small size allows compactluminaire designs and concentrated spreadangles. Low-voltage halogen lamps areavailable for different voltages (12/ 24 V)and in different shapes. Here too a selectioncan be made between clear lamps and various lamp and reflector combinations,or cool-beam reflector versions.

2.3 Light and light sources2.3.1 Incandescent lamps

50

The halogen and low-voltage halogen lampsmost commonly used in interior lighting.

Above (from left toright): low-voltage ha-logen bi-pin lamp andaluminium reflector, bi-pin and cool-beamglass reflector, withbayonet connectionand aluminium reflec-tor, with an aluminiumreflector for increasedpower.

Below (from left toright): halogen lampfor mains voltage withan E 27 cap and outerglass envelope, with a bayonet cap, and thedouble-ended version.Low-voltage halogenlamp with transverse filament and axial filament.

Page 51: ERCO HANDBOOK

2.3 Light and light sources2.3.1 Incandescent lamps

51

Single and double-ended halogen lampsfor mains voltage.

Low-voltage halogenlamps, clear, with metal reflector or withcool-beam reflector.

General service lamps,reflector lamps andtwo standard PARlamps for mains voltagewith data regardinglamp classification, power P, luminous flux Ï,lamp length l and lampdiameter d.

General service lampDes. P (W) (lm) l (mm) d (mm)A60 60 730 107 60A60 100 1380 107 60A65 150 2220 128 65A80 200 3150 156 80Cap: E27/E40 Lamp life 1000 h

LV halogen lampDes. P (W) (lm) l (mm) d (mm)QT9 10 140 31 9

20 350Cap: G4 Lamp life 2000 h

LV halogen reflector lampDes. P (W) (lm) l (mm) d (mm)QR38 20 7000 38 38QR58 50 18000 59 58Cap: B15d Lamp life 2000 h

LV halogen lampDes. P (W) (lm) l (mm) d (mm)QT12 50 950 44 12

75 1600100 2500

Cap: GY6.35 Lamp life 2000 h

LV halogen reflector lampDes. P (W) (lm) l (mm) d (mm)QR70 20 5000 50 70

75 1500075 19000

Cap: B15d Lamp life 2000 h

LV halogen reflector lampDes. P (W) (lm) l (mm) d (mm)QR111 50 20000 45 111

75 25000100 45000

Cap: G53 Lamp life 2000 h

LV halogen cool-beam reflector lamp Des. P (W) (lm) l (mm) d (mm)QR-CB51 20 8000 45 51QR- 35 13000CB51 50 15000

65/70 20000Cap: GX5.3 Lamp life 3000 h

LV halogen cool-beam reflector lamp Des. P (W) (lm) l (mm) d (mm)QR-CB35 20 5000 37/44 35QR- 35 8000CB35

Cap: GZ4 Lamp life 2000 h

Halogen lampDes. P (W) (lm) l (mm) d (mm)QT32 75 1050 85 32

100 1400 85150 2500 105250 4200 105

Cap: E27 Lamp life 2000 h

Halogen lampDes. P (W) (lm) l (mm) d (mm)QT18 75 1050 86 18

100 1400 86150 2500 98250 4200 98

Cap: B15dLamp life 2000 h

Halogen lampDes. P (W) (lm) l (mm) d (mm)QT-DE12 100 1650 75 12

150 2500 75200 3200 115300 5000 115500 9500 115

Cap: R7s-15 Lamp life 2000 h

Reflector lampDes. P (W) (lm) l (mm) d (mm)R63 60 650 103 63R80 100 1080 110 80R95 100 1030 135 95Cap: E27 Lamp life 1000 h

Parabolic reflector lampDes. P (W) (lm) l (mm) d (mm)PAR38 60 600 136 122

80 800120 1200

Cap: E27 Lamp life 2000 h

Parabolic reflector lampDes. P (W) (lm) l (mm) d (mm)PAR56 300 3000 127 179Cap: GX16d Lamp life 2000 h

Page 52: ERCO HANDBOOK

2.3 Light and light sources2.3.2 Discharge lamps

2.3.2 Discharge lamps

In contrast to incandescent lamps, lightfrom discharge lamps is not produced by heating a filament, but by exciting gasesor metal vapours. This is effected by app-lying voltage between two electrodes located in a discharge tube filled with inertgases or metal vapours. Through the voltage current is produced between the two electrodes. On their way through thedischarge tube the electrons collide withgas atoms, which are in turn excited to radiate light, when the electrons aretravelling at a sufficiently high speed. Forevery type of gas there is a certain wave-length combination; radiation, i.e. light, is produced from one or several narrowfrequency ranges.

If the speed of the electrons increases,the gas atoms are no longer excited on collision, but ionised; the gas atom is de-composed to create a free electron and apositively charged ion. The number of electrically charged, effective particles inthe discharge tube is accordingly increased,giving rise to a corresponding increase in radiation.

It soon becomes evident that dischargelamps have different properties to incan-descent lamps. This applies in the firstplace to the means by which the light ofthe respective lamp is produced. Whereasincandescent lamps have a continuousspectrum dependent on the temperatureof the filament, discharge lamps producea spectrum with narrow bands that aretypical for the respective gases or metalvapours. The spectral lines can occur in all regions of the spectrum, from infraredthrough the visible region to ultraviolet.The number and distribution of the spec-tral lines results in light of different lumi-nous colours. These can be determined bythe choice of gas or metal vapour in the discharge tube, and as a result white lightof various colour temperatures can beproduced. Moreover, it is possible to ex-ceed the given limit for thermal radiatorsof 3650 K and produce daylight-qualitylight of higher colour temperatures. An-other method for the effective productionof luminous colours is through the application of fluorescent coatings on theinterior surfaces of the discharge tube. Ultraviolet radiation in particular, whichoccurs during certain gas discharge pro-cesses, is transformed into visible light bymeans of these fluorescent substances,through which specific luminous colourscan be produced by the appropriate selection and mixing of the fluorescentmaterial.

The quality of the discharge lamp canalso be influenced by changing the pressureinside the discharge tube. The spectral lines spread out as the pressure increases,approaching continuous spectral distribu-tion.This results in enhanced colour renderingand luminous efficacy.

Apart from the differences in the kind of light they produce, there are alsodifferences between incandescent and discharge lamps when it comes to operatingconditions. Incandescent lamps can berun on the mains without any additionalcontrol gear. They produce lightas soon as they are switched on. In the caseof discharge lamps, however, there are various special ignition and operating conditions.

To ignite a discharge lamp there mustbe sufficient electron current in the discharge tube. As the gas that is to be exci-ted is not ionised before ignition, theseelectrons must be made available via aspecial starting device. Once the dischargelamp has been ignited there is an avalanche-like ionisation of the excited gases, which in turn leads to a continuously increasingoperating current, which would increaseand destroy the lamp in a relatively shorttime. To prevent this from happening the operating current must be controlledby means of a ballast.

Additional equipment is necessary forboth the ignition and operation of dischargelamps. In some cases, this equipment isintegrated into the lamp; but it is normallyinstalled separate from the lamp, in theluminaire.

The ignition behaviour and performanceof discharge lamps depend on the operatingtemperature; in some cases this leads to lamp forms with additional glass bulbs.If the current is interrupted it is usuallynecessary to allow the lamp to cool downfor a while before restarting it. Instantreignition is only possible if the startingvoltage is very high. There are special re-quirements for some of the lamps regardingthe burning position.

Discharge lamps can be divided into twomain groups depending on the operatingpressure. Each of these groups has different properties. One group compriseslow-pressure discharge lamps. Theselamps contain inert gases or a mixture of inert gas and metal vapour at a pressurewell below 1 bar. Due to the low pressureinside the discharge tube there is hardly any interaction between the gas molecules.The result is a pure line spectrum.

The luminous efficacy of low-pressuredischarge lamps is mainly dependent onlamp volume. To attain adequate luminouspower the lamps must have large dischargetubes.

High-pressure discharge lamps, on theother hand, are operated at a pressurewell above 1 bar. Due to the high pressureand the resulting high temperatures there is a great deal of interaction in the discharge gas. Light is no longer radiatedin narrow spectral lines but in broaderfrequency ranges. In general, radiationshifts with increasing pressure into the long-wave region of the spectrum.

The luminous power per unit of volumeis far greater than that of a low-pressure

52

Page 53: ERCO HANDBOOK

1 2 3

45 6

7

100

80

60

40

20

Se(%)

800200 400¬ (nm)

600

V (¬)T = 2700 KRa = 95

100

80

60

40

20

400 500 600 700 800

Se(%)V (¬)

¬ (nm)

100

80

60

40

20

400 500 600 700 800

T = 3800 KRa = 95

Se(%)V (¬)

¬ (nm)

V (¬) T = 5000 KRa = 98

100

80

60

40

20

400 500 600 700 800

Se(%)

¬ (nm)

2.3 Light and light sources2.3.2 Discharge lamps

discharge; the discharge tubes are small.High-pressure discharge lamps – similar toincandescent lamps – are point sourceswith high lamp luminance. As a rule theactual discharge tubes are surrounded byan additional outer envelope, which stabilises the operating temperature of thelamp, or, if necessary, serves as a UV filterand can be used as a means of containingthe fluorescent coating.

2.3.2.1 Fluorescent lamps

The fluorescent lamp is a low-pressure discharge lamp using mercury vapour.It has an elongated discharge tube with anelectrode at each end. The gas used to fill the tube comprises inert gas, which ignites easily and controls the discharge,plus a small amount of mercury, the vapour of which produces ultraviolet radia-tion when excited. The inner surface of the discharge tube is coated with a flu-orescent substance that transforms the ultraviolet radiation produced by thelamp into visible light by means of fluore-scence.

To facilitate ignition of the fluores-cent lamp the electrodes usually take theform of wire filaments and are coatedwith metallic oxide (emissive material) thatpromotes the flow of electrons. The electrodes are preheated at the ignitionstage, the lamp ignites when the voltageis applied.

Different luminous colours can beachieved through the combination of ap-propriate fluorescent materials. To achievethis three different luminous substancesare frequently combined, which, when mixed together, produce white light. Depending on the composition of the luminous substances, a warm white, neutralwhite or daylight white colour is pro-duced.

In contrast to point sources (see incandes-cent lamps, above) the light from fluores-cent sources is radiated from a larger surface area. The light is predominantlydiffuse, making it more suitable for theuniform illumination of larger areas thanfor accent lighting.

The diffuse light of the fluorescent lampgives rise to soft shadows. There are no sparkling effects on glossy surfaces.Spatial forms and material qualities are therefore not emphasised. Fluorescentlamps produce a spectrum, which is notcontinuous, which means that they havedifferent colour rendering compared withincandescent lamps. It is possible to pro-duce white light of any colour temperatureby combining fewer fluorescent materials,but this light still has poorer colour rendering properties than light with acontinuous spectrum due to the missingspectral components. To produce fluores-cent lamps with very good colourrendering properties more luminous sub-

53

When leaving the elec-trode (1) the electrons(2) collide with mercuryatoms (3). The mercuryatoms (4) are thus excited and in turn pro-duce UV radiation (5).The UV radiation istransformed into visiblelight (7) in the fluorescent coating (6).

Relative spectral dis-tribution Se (¬) of low-pressure discharge of mercury vapour. The radiation produced is to a large extent beyond the spectral sensitivity of the eye V (¬).

Relative spectral distri-bution Se (¬) of standardfluorescent lamps withvery good colour rende-ring in warm white(above), neutral white(centre) and daylightwhite (below).

Page 54: ERCO HANDBOOK

6000 t (h)3000 9000 12000

100

80

60

40

20

N (%)

EBCB

6000 t (h)3000 9000 12000

100

80

60

40

20

(%)ÏA

EBCB

80

100

120%

80 100 120

P

U (%)

Ï

20

60

100

20 40 60 80 100

Ï (%)

U (%)

20

60

100

-20 0 20 40(˚C)T

Ï (%)

50

100

150t (%)

10 20 30N (1/d)

T26 18W, 36W, 58W

100

80

60

40

20

6000 t (h)3000 9000 12000

EB

CB

Ï (%)

2.3 Light and light sources2.3.2 Discharge lamps

stances have to be combined in such a way that the spectral distribution corre-sponds as closely as possible to that of acontinuous spectrum.

Fluorescent lamps have a high luminousefficacy. They have a long lamp life, butthis reduces considerably the higher the switching rate.Both ignitors and ballastsare required for the operation of fluores-cent lamps. Fluorescent lamps ignite immediately and attain full power within ashort period of time. Instant reignition is possible after an interruption of current. Fluorescent lamps can be dimmed.There are no restrictions with regard toburning position.

Fluorescent lamps are usually tubular inshape, whereby the length of the lamp is dependent on the wattage. U-shaped orring-shaped fluorescents are available for special applications. The diameter of thelamps is 26 mm (and 16 mm). Lamp types with a diameter of 38 mm are of littlesignificance.

Fluorescent lamps are available in awide range of luminous colours, the mainones being warm white, neutral white anddaylight white. There are also lamps avai-lable for special purposes (e.g. for lightingfood displays, UV lamps) and colouredlamps. The colour rendering properties of fluorescents can be improved at the costof the luminous efficacy; enhanced lumi-nous efficacy therefore means a deteriora-tion in the colour rendering quality.

Fluorescent lamps are usually ignitedvia an external starting device and preheated electrodes. Some models have integrated ignition, which means that they can do without a starting devicealtogether. These are mainly used inenclosed luminaires, for environments wherethere is a risk of explosion.

2.3.2.2 Compact fluorescent lamps

Compact fluorescent lamps do not functionany differently from conventional fluorescent lamps, but they do have amore compact shape and consist of eitherone curved discharge tube or the combination of several short ones. Somemodels have an outer glass envelope around the discharge tube, which changesthe appearance and the photometric pro-perties of the lamp.

Compact fluorescent lamps basicallyhave the same properties as conventionalfluorescents, that is to say, above all, high luminous efficacy and a long lamp life.Their luminous efficiency is, however, limited due to the relatively small volumeof the discharge tube. The compact form does offer a new set of qualities andfields of application. Fluorescent lamps inthis form are not only confined to applica-tion in louvred luminaires, they can also be used in compact reflector luminaires(e.g. downlights). This means that concentra-

54

Proportion of operatinglamps N, lamp lumens Ïand luminous flux oftotal installation ÏA(as the product of bothvalues) as a function of the operating time t.Through the applica-tion of electronic control gear (EB) theoperating quality ofthe lamps is improvedby comparison with the operation withconventional controlgear (CB).

Effect of overvoltageand undervoltage onrelative luminous flux Ïand electrical power P.

Relative luminous flux Ïof fluorescent lamps as a function of voltage.

The effect of ambienttemperature T on lamplumens Ï.

Lamp life t as a func-tion of switching frequency per day N. Nominal lamp life of 100 % is achieved at a switching rate of 8 times every 24 hours.

Comparison of lengthsof standard T26 fluore-scent lamps.

Page 55: ERCO HANDBOOK

TC-L 18W, 24W, 36W, 40/55W

TC 5W, 7W, 9W, 11W TC-D 10W, 13W, 18W, 26W

2.3 Light and light sources2.3.2 Discharge lamps

ted light can be produced to accentuatethe qualities of illuminated objects bycreating shadows.

Compact fluorescent lamps with anintegrated starting device cannot be dimmed, but there are models available with external igniting devices and four-pinbases that can be run on electronic controlgear, which allows dimming.

Compact fluorescent lamps are mainlyavailable in the form of tubular lamps, in which each lamp has a combination oftwo or four discharge tubes. Starting device and ballast are required to operatethese lamps; in the case of lamps withtwo-pin plug-in caps the starting device isintegrated into the cap.

Alongside the standard forms equippedwith plug-in caps and designed to be runon ballasts, there is a range of compactfluorescent lamps with integrated startingdevice and ballast; they have a screw cap and can be used like incandescentlamps. Some of these lamps have an additional cylindrical or spherical glass bulbor cover to make them look more like incandescent lamps. If these lamps are used in luminaires designed to take incandescent lamps it should be noted thatthe luminaire characteristics will be compromised by the greater volume of thelamp.

2.3.2.3 High-voltage fluorescent tubes

High-voltage fluorescent tubes work onthe principle of low-pressure gas discharge,the gas being either an inert or rare gas or a mixture of inert gas and mercury vapour. In contrast to fluorescent lamps,the electrodes contained in these lampsare not heated, which means they have to be ignited and run on high voltage. As there are special regulationsconcerning installations run at 1000 Vand more, high-voltage tubular lamps are usually operated at less than 1000 V.There are, however, high-voltage dis-charge lamps available that run at over1000 V.

High-voltage fluorescent tubes have aconsiderably lower luminous efficacy thanconventional fluorescent lamps, but theyhave a long lamp life. Rare-gas dischargedoes not allow much scope when it comes to producing different colours; red can be produced using neon gas orblue using argon. To extend the spectrumof colours available it is possible to usecoloured discharge tubes. However, mer-cury is usually added to the inert gas andthe resulting ultraviolet radiation trans-formed into the desired luminous coloursusing fluorescent material. High-voltagefluorescent tubes require a ballast; they are operated on leakage transformers,which manage the high voltages requiredfor ignition and operation. High-voltage

55

Arrangement of tubesin compact fluorescentlamps: TC/TC-L (above),TC-D (centre), TC-DEL(below).

Compact fluorescentlamps with two-pinplug-in cap and inte-gral starting device(above), four-pin plug-in cap for operation on electronic controlgear (centre), screw capwith integral ballastfor mains operation(below).

In contrast to con-ventional fluorescentlamps, in the case ofcompact fluorescentsboth ends of the discharge tube(s) aremounted on a singlecap.

Comparison of sizes of standard TC, TC-Dand TC-L compact fluore-scent lamps.

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100

80

60

40

20

2 4t (min)

10 1286

Ï (%)

Se (%)100

80

60

40

20

400 500 600 700 ¬(nm)800

V (¬)

LST 35 W, 90 W

100

80

60

40

20

t (h)5000 7500 100002500

ÏA (%)

100

80

60

40

20

t (h)5000 7500 100002500

Ï (%)

100

80

60

40

20

t (h)5000 7500 100002500

N (%)

2.3 Light and light sources2.3.2 Discharge lamps

fluorescent tubes ignite instantly and theycan be restarted when hot. There are no restrictions with regard to burningposition.

High-voltage fluorescent tubes comein various diameters and lengths. Diffe-rent tubular shapes can be manufacturedto meet the requirements of specific applications, e.g. for written signs and com-pany logos. They are available in a varietyof colours.

2.3.2.4 Low-pressure sodium lamps

Low-pressure sodium lamps are comparableto fluorescent lamps in the way they areconstructed and how they operate. In thiscase sodium vapour is excited instead of mercury vapour. This leads to a numberof essential differences to fluorescentlamps. In the first place, sodium lamps aremore difficult to ignite than mercurylamps, because solid sodium – as opposedto liquid mercury – does not produce metal vapour at room temperature. In thecase of sodium lamps, ignition can onlybe effected with the aid of additionalinert gas; only when the rare-gas dischargeproduces sufficient heat does the sodiumbegin to evaporate, thereby enabling the actual metal vapour discharge to takeplace. Low-pressure sodium lamps requirehigh ignition voltage and a relatively longrun-up time before they reach maximumefficacy. To guarantee a sufficiently highoperating temperature, the dischargetube is usually encased in a separate glassenvelope that is often designed to reflectinfrared radiation.

Another difference is the kind of lightthe lamp produces. Whereas mercury vapour excited at low pressure producesmainly ultraviolet radiation, which istransformed into light with the aid of fluorescent substances, sodium vapour pro-duces light directly. Low-pressure sodiumlamps therefore require no luminous substances to be added. Moreover, the luminous efficacy of these lamps is so high that the lamp volume required isconsiderably smaller than is the case forfluorescent lamps.

The most striking feature of low-pressuresodium lamps is their extraordinarily high luminous efficacy. As the low-pressuresodium lamp has a very long lamp life,it is the most economically efficient lightsource available.

Low-pressure sodium vapour only pro-duces light in two spectral lines which arevery close together; the light radiated by the lamp is monochrome yellow. Due toits monochromatic character it does notproduce any chromatic aberration in the eye and therefore guarantees visualacuity. The obvious disadvantage of theselamps with regard to the advantagesmentioned above is their exceptionallypoor colour rendering quality. Colour ren-

56

Relative spectral dis-tribution Se (¬) of low-pressure sodiumvapour discharge. The line spectrum produced is close tothe maximum spectral sensitivity of the eye,but limits colour rendering through its monochromaticcharacter.

Low-pressure sodiumlamp with U-shapeddischarge tube in adichroic glass bulb. Theinfrared radiation pro-duced by the lamp isreflected back into thedischarge tube via thedichroic coating on theglass, thereby cuttingdown the time requi-red to reach operatingtemperature.

Proportion of operatinglamps N, lamp lumens Ïand luminous flux of total installation ÏA(as the product of bothvalues) as a function of the operating time t.

Run-up characteristic:lamp lumens Ïin relation to time t.

Comparison of sizes of low-pressure sodiumlamps (LST).

Page 57: ERCO HANDBOOK

100

80

60

40

20

400 500 600 700 ¬(nm)800

V(¬)

Se (%) 100

80

60

40

20

t (h)5000 7500 100002500

N (%)

100

80

60

40

20

t (h)5000 7500 100002500

(%)Ï

100

80

60

40

20

t (h)5000 7500 100002500

(%)AÏ 100

80

60

40

20

2 4 6 t (min)

(%)Ï

HME 125W HMG 80W HMR 125W

2.3 Light and light sources2.3.2 Discharge lamps

dering in the usual sense does not exist.All that is perceived is saturated yellow invarious shades, from the pure colour to black. Low-pressure sodium lamps havetherefore been replaced by high-pressuresodium lamps to a great extent, especiallyin their main field of application: streetlighting.

A combination of ignitor and ballastis necessary to operate some of the tubularmodels, but usually a leakage transformeris used as a starting device and ballast.Low-pressure sodium lamps require arun-up time of a few minutes and a shortcooling time before re-ignition. Instantre-ignition is possible if special controlgear is used. There are restrictions regardingthe burning position.

Low-pressure sodium lamps are normallyU-shaped, sometimes also tubular, surrounded by an additional glass envelope.

2.3.2.5 High-pressure mercury lamps

High-pressure mercury lamps have a shortquartz glass discharge tube that containsa mixture of inert gas and mercury. Electrodes are positioned at both ends of the discharge tube. In close proximity to one of the electrodes there is an additional auxiliary electrode for the igni-tion of the lamp. The discharge tube is surrounded by a glass envelope that stabilises the lamp temperature and protectsthe discharge tube from corrosion. The outer glass can be provided with afluorescent coating to control the luminouscolour.

When the lamp is ignited, there is aninitial luminous discharge from the auxili-ary electrode which gradually extends to the second main electrode. When the gashas been ionised in this way, there is anarc discharge between the two main elec-trodes, which, at this point in time, is theequivalent of a low-pressure discharge.Only when all the mercury has been eva-porated via the arc discharge and the resulting heat has produced sufficient ex-cess pressure, does high-pressure dischargetake place and the lamp produce full power.

High-pressure mercury lamps have moderateluminous efficacy and a very long lamplife. As a light source they are relativelycompact, which allows their light to becontrolled via optical equipment.

The light produced by high-pressuremercury lamps is bluish-white in colour due to the lack of the red spectral range.Colour rendering is poor, but remainsconstant throughout the entire lamp life.A neutral white or warm white colour appearance and improved colour renderingproperties are achieved by the addition offluorescent materials.

Due to the integrated auxiliary elec-trode there is no need for high-pressure

57

Proportion of operatinglamps N, lamp lumens Ïand luminous flux of total installation ÏA(as the product of both values) as a function ofthe operating time t.

Standard high-pressuremercury lamps with elliptical bulb (HME),spherical bulb (HMG)and integrated reflec-tor (HMR).

Relative spectral dis-tribution Se (l) of high-pressure mercurylamps.

High-pressure mercurylamp with quartz glassdischarge tube and elliptical bulb. As a rulethe bulb is coated witha layer of fluorescentmaterial which trans-

forms the UV radiationproduced by the lampinto visible light, thereby improving luminous efficacy andcolour rendering.

Run-up characteristic:lamp lumens Ï in rela-tion to time t.

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60

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20

¬(nm)400 500 600 700 800

V(¬)

Se (%) 100

80

60

40

20

2000 4000 t (h)6000

N (%)

100

80

60

40

20

2000 4000 t (h)6000

Ï(%)

100

80

60

40

20

2000 4000 t (h)6000

Ï (%)A

1 2 3 t (min)

140

120

100

80

60

Ï(%)

HME-SB 160W HMR-SB 160W

2.3 Light and light sources2.3.2 Discharge lamps

mercury lamps to have an ignitor, butthey do have to be run on a ballast. High-pressure mercury lamps require a run up time of some minutes and a longercooling time before restriking. There areno restrictions as to the burning position.

High-pressure mercury lamps are availablein various shapes and sizes; the outer bulbscan be spherical, elliptical or mushroom-shaped, the latter versions being designedas reflector lamps.

2.3.2.6 Self-ballasted mercury lamps

Self-ballasted mercury lamps are basicallyconstructed in the same way as high-pressure mercury lamps. They have an additional filament in the outer glass bulb,however, which is connected in serieswith the discharge tube. The filament takeson the role of a current limiter, making an external ballast unnecessary. The warmwhite light produced by the filamentcomplements the missing red content in the mercury spectrum, which improvesthe colour rendering. Self-ballasted mercury lamps usually contain additionalfluorescent material to enhance the luminous colour and improve the luminousefficacy.

Self-ballasted mercury lamps have similarqualities to high-pressure mercury lamps. Luminous efficacy and lamp life rates are not so good, however, with the conse-quence that they are seldom used for architectural lighting. Since they requireno ignitor or control gear and are pro-duced with an E 27 cap, self-ballastedmercury lamps can be used as incandescentlamps.

The filament in self-ballasted mercurylamps radiates light immediately on ignition. After a few minutes the incande-scent component diminishes and themercury vapour discharge reaches full power.Following an interruption to the mainssupply self-ballasted mercury lamps require a cooling-off period. Self-ballastedmercury lamps cannot be dimmed. There are restrictions as to the burning positionfor certain lamp types.

Self-ballasted mercury lamps are availablewith an elliptical bulb or as mushroom-shaped reflector lamps.

58

Self-ballasted mercurylamp with a quartzglass discharge tubefor high-pressure mer-cury discharge and an additional filamentthat takes on the func-tion of preresistanceand supplements the spectrum in the redrange. The ellipticalbulb is frequently pro-vided with a coating oflight-diffusing mate-rial.

Run-up characteristic:lamp lumens Ïin relation to time t.

Proportion of functio-nal lamps N, lamp lumens Ï and luminousflux of overall installa-tion ÏA (as the productof both values) in rela-tion to the operatingtime t.

Standard self-ballastedmercury lamp with elliptical bulb (HME-SB),or integral reflector(HMR-SB).

Relative spectral dis-tribution Se (¬) of a self-ballasted mercurylamp with the combi-nation of the spectraproduced by the high-pressure mercury dis-charge and the fila-ment.

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80

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20

1 2 3 t (min)

Ï(%)

100

80

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2000 4000 t (h)6000

Ï(%)

< 13

81224

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2000 4000 t (h)6000

N (%)

100

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Ï(%)

100

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2000 4000 t (h)6000

Ï (%)A100

80

60

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20

300 400 500 600 ¬(nm)700

V(¬)

Se (%)

T = 4000 K

100

80

60

40

20

300 400 500 600 ¬(nm)700

V(¬)

Se (%)

T = 3000 K

100

80

60

40

20

300 400 500 600 ¬(nm)700

V(¬)

Se (%)

T = 5600 K

2.3 Light and light sources2.3.2 Discharge lamps

2.3.2.7 Metal halide lamps

Metal halide lamps are a further develop-ment of mercury lamps and are therefore similar to these with regard to constructionand function. Apart from mercury they also contain a mixture of metal halides. In contrast to pure metals, halogen compounds have the advantage that theymelt at a considerably lower temperature.This means that metals that do not produce metal vapour when the lamp is inoperation can also be used.

By adding metal halides, luminous efficacy is improved and, above all, colourrendering enhanced. If the metal combi-nations are correct then multi-line spectracan be produced, similar to those of fluorescent lamps; by using specific combi-nations it is possible to create a practicallycontinuous spectrum consistingof numerous of spectral lines. Additional fluorescent substances to enhance colourrendering are not necessary. The mercurycomponent primarily serves as an ignitionaid and to stabilise the discharge process;when the metal halides have been evaporated via the initial mercury vapourdischarge, these metal vapours essentiallyproduce light.

The presence of halogens inside thelamp bulb means that auxiliary electrodesare not required as part of a starting device. Metal halide lamps require externalcontrol gear.

Metal halide lamps have excellent lumi-nous efficacy and good colour renderingqualities; their nominal lamp life is high.They are extremely compact light sources,whose light can be easily controlled. The colour rendering and colour temperatureof metal halide lamps is, however, not constant; it varies between individuallamps in a range and changes depending onthe age of the lamp and the ambient conditions. This is particularly noticeablewhen it comes to the warm white lamps.

To operate metal halide lamps both an ignitor and a ballast are required. Theyrequire a run-up time of some minutesand a longer cooling time before restarting.Instant reignition is possible in the case of some double-ended types, but specialignitors or an electronic ballast is necessary. As a rule metal halide lampscannot dimmed. The burning position is usually restricted.

Metal halide lamps are available in warmwhite, neutral white and daylight white, as single or double-ended tubular lamps,as elliptical lamps and as reflector lamps.

59

Double-ended metalhalide lamp with com-pact discharge tubeand quartz glass outerenvelope.

Proportion of functionallamps N, lamp lumens Ïand luminous flux ofoverall installation ÏA(as the product of bothvalues) in relation to the operating time t.

Relative spectral dis-tribution Se (¬) of stan-dard metal halide lampwith luminous colourwarm white (above),neutral white (centre)and daylight white (be-low).

Decline in luminousflux Ï at differentswitching frequenciesof 24, 12, 8, 3 and < 1times per day.

Run-up characteristic:lamp lumens Ïin relation to time t.

Page 60: ERCO HANDBOOK

HSE 70W

HST 70W

HST 100W

HST-DE 150W

HIT 35W, 70W, 150W HIT 35W, 70W, 150W

HIT-DE 75W, 150W, 250W

HIE 100W

2.3 Light and light sources2.3.2 Discharge lamps

2.3.2.8 High-pressure sodium lamps

Similar to mercury lamps, the spectrumproduced by sodium lamps can also be extended by increasing the pressure. If the pressure is sufficiently high thespectrum produced is practically continuouswith the resultant enhanced colour ren-dering properties. Instead of the mono-chrome yellow light produced by the low-pressure sodium lamp, with the extremelypoor colour rendering properties, the lightproduced is yellowish to warm white pro-ducing average to good colour rendering.The improvement in colour rendering is,however, at the cost of luminous efficacy.High-pressure sodium lamps are comparableto mercury lamps with regard to theirconstruction and function. They also havea small discharge tube, which is in turnsurrounded by a glass envelope. Whereasthe discharge tube in high-pressure mercury lamps is made of quartz glass, thedischarge tube in high-pressure sodiumlamps is made of alumina ceramic, since high-pressure sodium vapours havean aggressive effect on glass. The lampsare filled with inert gases and an amalgam of mercury and sodium, suchthat the rare gas and mercury componentserve to ignite the lamp and stabilise thedischarge process.

The surrounding bulb of some high-pressure sodium lamps is provided with aspecial coating. This coating only servesto reduce the luminance of the lamp andto improve diffusion. It does not containany fluorescent materials.

The luminous efficacy of high-pressure sodium lamps is not so high as that of low-pressure sodium lamps, but higherthan that of other discharge lamps. These lamps have a long nominal lamp life.Colour rendering is average to good, distinctly better than that of monochromeyellow low-pressure sodium light.

High-pressure sodium lamps are runon a ballast and require an ignition device.They require a run-up time of some minutes and cooling time before restarting.Instant re-ignition is possible in the caseof some double-ended types, but specialignition devices or an electronic ballast is necessary. As a rule there are no restrictions as to the burning position.

High-pressure sodium lamps are availableas clear glass tubular lamps or with speci-ally coated ellipsoidal bulbs. They are alsoavailable as compact, double-ended lineartype lamps, which allow instant reignitionand form an especially compact light source.

60

Standard high-pressuresodium lamps, single-ended elliptical (HSE),tubular (HST), anddouble-ended tubular(HST-DE).

Standard metal halidelamps, single-ended(HIT) and double-endedversions (HIT-DE), pluselliptical version (HIE).

Single-ended high-pressure sodium lampwith ceramic dischargetube and additional outer glass envelope.

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40

20

400 500 600 700¬(nm)

800

100

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6000 t (h)3000 9000 12000

N (%)

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80

60

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20

Ï(%)

6000 t (h)3000 9000 12000

100

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60

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20

6000 t (h)3000 9000 12000

Ï (%)A 100

80

60

40

20

2 4 6 t (min)

Ï(%)

2.3 Light and light sources2.3.2 Discharge lamps

61

Relative spectral distri-bution Se (¬) of high-pressure sodium lamps.By increasing the pres-sure the spectrum isinverted, in contrast tolow-pressure discharge.The result is wide spec-tral distribution with a minimum in the low-pressure sodium lamps.

Proportion of functionallamps N, lamp lumens Ïand luminous flux ofoverall installation ÏA(as the product of bothvalues) in relation to the operating time t.

Run-up characteristic:lamp lumens Ïin re-lation to time t.

Page 62: ERCO HANDBOOK

2.3 Light and light sources2.3.2 Discharge lamps

62

Tubular fluorescent lamp (diameter 26 mm),of standard power.

Single-ended low-pressure sodium lampin the standard form with U-shapeddischarge tube.

High-pressure mercurylamps and self-ballastedmercury lamps, both lamp types withan ellipsoidal outer envelope and as a reflector lamp. Choice of power for interiorlighting including dataon lamp description;power P, luminous flux Ï,length of lamp Iand lamp diameter d.

Compact fluorescentlamps in the standardshapes TC, TC-D and TC-L, and with integral electronic ballast and E 27 cap: TC-DEL.

Fluorescent lampDes. P (W) (lm) l (mm) d (mm)T26 18 1350 590 26

30 2400 89536 3350 120038 3200 104758 5200 1500

Cap: G13 Lamp life 7000 h

Compact fluorescent lampDes. P (W) (lm) l (mm) d (mm)TC-L 18 1200 225 17

24 1800 32036 2900 41540 3500 53555 4800 535

Cap: 2G11 Lamp life 8000 h

Compact fluorescent lampDes. P (W) (lm) l (mm) d (mm)TC-DEL 9 400 127

11 600 14515 900 17020 1200 19023 1500 210

Cap: E27 Lamp life 8000 h

Compact fluorescent lampDes. P (W) (lm) l (mm) d (mm)TC 7 400 138 12

9 600 16811 900 238

Cap: G23 Lamp life 8000 h

Compact fluorescent lampDes. P (W) (lm) l (mm) d (mm)TC-DEL 15 900 148 58

20 1200 16823 1500 178

Cap: E27 Lamp life: 8000 h

Compact fluorescent lampDes. P (W) (lm) l (mm) d (mm)TC-D 10 600 118 12

13 900 15318 1200 17326 1800 193

Cap: G24 Lamp life 8000 h

Mercury lampDes. P (W) (lm) l (mm) d (mm)HME 50 2000 130 55

80 4000 156 70125 6500 170 75250 14000 226 90

Cap: E27/E40 Lamp life 8000 h

Mercury reflector lampDes. P (W) (lm) l (mm) d (mm)HMR 80 3000 168 125

125 5000Cap: E27 Lamp life 8000 h

Self-ballasted mercury lampDes. P (W) (lm) l (mm) d (mm)HME-SB 160 3100 177 75Cap: E27 Lamp life 5000 h

Self-ballasted mercury reflector lampDes. P (W) (lm) l (mm) d (mm)HMR-SB 160 2500 168 125Cap: E27 Lamp life 5000 h

Low-pressure sodium lampDes. P (W) (lm) l (mm) d (mm)LST 35 4800 310 54

55 8000 425 5490 13500 528 68

Cap: BY22d Lamp life 10000 h

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2.3 Light and light sources2.3.2 Discharge lamps

63

Metal halide lamp, asan ellipsoidal and reflector lamp and assingle and double-ended versions. Choiceof standard wattagesfor interior lighting.

High-pressure sodiumlamp, ellipsoidal plustubular, single-endedand double-ended versions. Choice ofstandard wattages forinterior lighting.

High-pressure sodium lampDes. P (W) (lm) l (mm) d (mm)HSE 50 3500 156 70

70 5600 156 70100 9500 186 75150 14000 226 90250 25000 226 90

Cap: E27/E40 Lamp life 10000 h

High-pressure sodium lampDes. P (W) (lm) l (mm) d (mm)HST 50 4000 156 37

70 6500 156 37100 10000 211 46150 17000 211 46250 33000 257 46

Cap: E27/E40 Lamp life 10000 h

Metal halide lampDes. P (W) (lm) l (mm) d (mm)HIE 75 5500 138 54

100 8500 138 54150 13000 138 54250 17000 226 90

Cap: E27/E40 Lamp life 5000 h

Metal halide reflector lampDes. P (W) (lm) l (mm) d (mm)HIR 250 13500 180 125Cap: E40 Lamp life 6000 h

Metal halide lampDes. P (W) (lm) l (mm) d (mm)HIT 35 2400 84 26

70 5200150 12000

Cap: G12/PG12 Lamp life 5000 h

Metal halide lampDes. P (W) (lm) l (mm) d (mm)HIT-DE 75 5500 114 20

150 11250 132 23250 20000 163 25

Cap: RX7s Lamp life 5000 h

High-pressure sodium lampDes. P (W) (lm) l (mm) d (mm)HST 35 1300 149 32

70 2300100 4700

Cap: PG12 Lamp life 5000 h

High-pressure sodium lampDes. P (W) (lm) l (mm) d (mm)HST-DE 70 7000 114 20

150 15000 132 23Cap: RX7s Lamp life 10000 h

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2.3 Light and light sources2.3.2 Discharge lamps

64

Compact fluorescentlamp with integral ballast and screw cap.This lamp is mainlyused domestically asan economic alterna-tive to the incandes-cent lamp

Discharge tube contai-ning a mixture of rare earth gases and low-pressure mercury vapour

Fluorescent material for transforming ultra-violet radiation into visible light

Insulated contact forconnection to the phase

Screw cap to secure lampmechanically, also servesas a contact to the neutralconductor

Integral electronic ballast

Heated coil electrode

Page 65: ERCO HANDBOOK

N L

2.4 Control gear and control equipment2.4.1 Discharge lamps

Controlgear and controlequipment

In addition to lamps and luminaires sup-plementary equipment is often required inorder for a lighting installation to function.The most important additional equipment is control gear, which is necessary for theoperation of many lamp types.

Lighting control equipment, on theother hand, is not required to operatethe luminaires. It is used to switch luminaireson and off and to control their brightness– and sometimes also other luminairecharacteristics.

2.4.1 Control gear for discharge lamps

Typical of all discharge lamps is theirnegative current versus voltage characte-ristic, i.e. the lower the voltage the higher the operating current. In contrast toincandescent lamps, where the filament acts as a current limiting device, the ope-rating current in the case of dischargelamps is constantly on the increase due tothe avalanche ionisation effect of theinert gas, which if left uncontrolled wouldresult in the destruction of the lamp.

To operate discharge lamps it is there-fore necessary to use a ballast to limit the current. In their simplest form these areohmic current limiters. This type of currentlimiting device is not frequently used, however, since it tends to heat up, whichin turn leads to substantial energy con-sumption; they are occasionally used forself-ballasted mercury lamps, which use a filament as an ohmic current limiter.

Current limitation using super-imposedcapacitors – i.e. via capacitive reactance –reduces the loss of energy,but decreases the lamp life, so is similarly not a popularsolution. In practice, current limitation is mainly effected via the application of inductive current limiting devices suchas lag ballasts or transformers, especiallyas this kind of ballast has the added advantage that it can be used to producethe striking voltage to ignite the lamp.High-frequency electronic control gear isgaining importance alongside inductiveballasts. Besides their function as currentlimiting devices electronic ballasts alsoserve as ignitors and ensure that the lampoperates more effectively.

The ignition voltage of discharge lampsis well above their operating voltage and usually also above the mains voltageprovided. Special equipment is therefore required to ignite the lamps. This may bea matter of auxiliary electrodes built intothe lamp that ionise the gas in the lampvia a luminous discharge. However, ignition is usually effected via a voltagesurge, which can be produced inductivelyby the starter and the ballast, but a leakage transformer or an ignitor is requiredin the case of higher ignition voltages.

More recently both electronic startersand electronic ignition devices have be-come available.

2.4.1.1 Fluorescent lamps

Fluorescent lamps can be operated on aconventional ballast (CB) and a starter. In this case the ballast functions as an in-ductive resistor; it comprises a lag ballastwhich consists of a laminate iron core anda copper-wire winding.

Conventional ballasts are the cheapestkind of ballasts, but they do give riseto significant losses of energy due to the generation of heat.

Low loss ballasts (LLB) are comparable toconventional ballasts, except that theircore material is of a higher quality and theyhave thicker copper wires to reduce the loss of energy in the control gear. Lowloss ballasts are only slightly more expen-sive than conventional ballasts, so they are frequently used in lieu of the latter.

Electronic ballasts (EB) differ in weight,form and function from conventional, inductive ballasts. They consist of a filter,which prevents any reactive feedbackonto the mains supply, a rectifier and ahigh-frequency inverter.

Electronic ballasts have an integratedignition device, which means that no additional ignitor is required. They ensurea flicker-free start and switch off auto-matically if the lamp is defective, whichprevents the ignitor being activated timeand again; switching and operation are as trouble-free as with incandescentlamps.

Operating the lamps at 25–40 kHzpresents a number of advantages, aboveall, enhanced luminous efficacy. This in turn means that the luminous power isachieved, but at a lower energy con-sumption. At the same time there is con-siderably less power loss. The high opera-ting frequency of the lamps also preventsstroboscopic and flicker effects, and magnetic interference and humming, allof which are associated with conventionalballasts.

Electronic ballasts are to a large ex-tent insensitive to voltage and frequencyfluctuations. They can be operated at both 50 and 60 Hz and over a voltagerange of between 200 and 250 V. As theyare also designed to be run on direct current, fluorescent lamps with EBs canbe operated on batteries, should there bea current failure, thereby simplifying the provision of emergency lighting. Electronic ballasts are, however, more ex-pensive than inductive ballasts.

If fluorescent lamps are operated using in-ductive ballasts it is necessary to provide a separate starter. The starter first preheatsthe lamp electrodes. Once the electrodesare sufficiently heated the starter breaksthe circuit. This induces a voltage surge inthe ballast which in turn ignites the lamp.The simplest form of ignitors are glow starters. They comprise bimetal electrodes

65

2.4

Circuit diagram of afluorescent lamp withan inductive ballast and ignition device(not power-factorcorrected).

Page 66: ERCO HANDBOOK

10

30

70

50

T 18W T 36W T 58W

CBLLBEB

P (W)

Ballast

Lamp

2.4 Control gear and control equipment2.4.1 Discharge lamps

encased in a glass tube filled with inert gas.Switching the lamp on produces a lu-minous discharge between the electrodesin the starter, which in turn heats up the electrodes. During this process the bi-metal electrodes bend inwards until theytouch, thereby closing the heater or filament circuit of the fluorescent lamp. After a short time the starter electrodescool down and separate. This disconnectioninduces a voltage surge in the ballastwhich in turn ignites the lamp. When thelamp has been ignited it is only the opera-ting voltage of the lamp that is applied to the starter. This is insufficient to pro-duce a luminous discharge in the starter. The electrodes therefore remainopen, which avoids the lamps being per-manently heated.

Glow starters are the starters mostfrequently used and they are the most economical. They do have one drawback:they repeatedly try to ignite the lamp inthe event of it being defective. This givesrise to noise and flickering lamps. More-over, ignition problems may arise inthe case of undervoltage or low ambient temperatures due to the fact that thepreheating times are inadequate.

Safety starter switches are similar to glowstarters. They switch off automatically after repeated attempts to ignitethe lamp, thereby ensuring that defective lamps are not subjected to continuous ignition. To operate the starter again it is necessary to reset the safety switch manually.

Thermal starters have contacts that arenormally closed when the lamp is switchedon. The contacts are disconnected by means of an additional heating elementwhich heats up a bimetal strip or dilatingwire. The starter only opens when it hasbeen sufficiently preheated and since thepreheating time is prolonged if thetemperature or the voltage conditions arenot ideal, ignition is not always trouble-free. As there is no need for an initial warm up period to the point of contact,the result is that thermal starters ignitefaster than glow starters. Thermal startersare more expensive than glow starters.Some versions require a separate heatingcurrent supply through the ballast.

Electronic starters open and close the pre-heating circuit without any mechanicalcontacts. They ensure a quick and safe start under a much wider range of conditions; in the case of defective lampsthe re-ignition process is terminated.

2.4.1.2 Compact fluorescent lamps

Compact fluorescent lamps are operatedon the same ballasts as conventional fluorescent lamps. In the case of lampswith a bipin base the starter is integrated,

so they can be operated on inductive ballasts without an additional ignitiondevice. Lamps with four-pin bases can be operated on an inductive ballastwith a separate starter or on an electronicballast.

2.4.1.3 High-voltage fluorescent tubes

High-voltage fluorescent tubes require anoperating voltage that is considerablyhigher than mains voltage. They are therefore run on a leakage transformer,which handles the ignition with its highopen potential, and then reduces the voltage during the operation of the lamp.Additional starters or ignition devices arenot necessary.

Special regulations have to be obser-ved in Germany (VDE 0128, 0713, 0250)for high-voltage fluorescent tubes run at 1000 V and above. Planners preferto opt for installations comprising shorterhigh-voltage fluorescent tubes and voltages below 1000 V, which only haveto meet the requirements laid down for low-voltage installations (VDE 0100).

2.4.1.4 Low-pressure sodium lamps

Some linear type low-pressure sodiumlamps –similar to fluorescent lamps–can be run on chokes or inductive ballastswith an additional starter. As a rule, ignition and operating voltage are sohigh, however, that a leakage transformeris used to handle ignition and current limitation.

2.4.1.5 High-pressure mercury lamps

High-pressure mercury lamps are ignitedusing a glow discharge through an auxili-ary electrode. Additional starters or igni-tion devices are therefore not required.Current limitation is controlled via induc-tive ballasts, as for fluorescent lamps.These ballasts must, however, be designedto handle the higher operating current.

2.4.1.6 Metal halide lamps

Metal halide lamps are run on inductiveballasts. An extra ignition device is generally required (e.g. impulse generator).

Instant re-ignition of the lamps aftera power failure is required in the case ofthe lighting of certain traffic installationsand meeting places. Double-ended metalhalide lamps are equipped with special ignitors which supply the necessary highignition voltages that make an instant restart possible.

Electronic control gear is also availablefor metal halide lamps. They have similarproperties and advantages to the electronicballasts for fluorescent lamps, while at the

66

Power consumption P(lamp power and power loss of ballast)of standard fluorescentlamps run on conven-tional (CB), low-loss(LLB) and electronicballasts (EB).

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N L

N L

N L

2.4 Control gear and control equipment2.4.2 Compensation2.4.3 Radio interference suppression

same time allowing an instant restart afterpower failure.

2.4.1.7 High-pressure sodium lamps

High-pressure sodium lamps are operated oninductive ballasts. An ignition device is required due to their high ignition voltage.

Some double-ended lamps do allowan instant restrike when the lamps are still warm. As with metal halide lamps, aspecial ignitor is necessary for theselamps to handle the required high ignitionvoltages and the installation must be designed to take these voltages. Electronicballasts are also available for high-pressuresodium lamps.

2.4.2 Compensation and wiring of discharge lamps

Inductive ballasts produce a certain amountof idle current due to the phase shift of the voltage with respect to the current– they have a power factor (cos f) sub-stantially below 1. Since idle current loadsthe mains, power supply companies require the idle current to be compensa-ted – i.e. to a power factor to approachunity – in the case of large-scale lightinginstallations. Compensation is effected by means of capacitors, which balance thephase shift caused by the reactance. It ispossible to compensate individual lumin-aires, groups of luminaires or an entire installation. Compensation is not necessaryin the case of electronic ballasts, as they effectively have a unity power factor.

Fluorescent lamps that are run on induc-tive ballasts can be compensated via capacitors that are connected in parallelto or in series with the ballast.

If a compensating capacitor is connectedin series with the ballast, we talk about a capacitive circuit. The power factor in this case is well above unity and so thistype of circuit is referred to as an over-compensated circuit. Circuits of this kindallow a second lamp with a non-compensated ballast to be operated at thesame time. Such circuits are known as twin-start circuits. The advantage of atwin-start circuit is that both lamps areout-of-phase. This means that stroboscopicor flickering effects at workplaces with rotating machine parts, for example,are avoided. Sequential connection of the lamps to a three-phase supply networkwill also minimize these effects.

Ballasts without compensating capa-citors are referred to as inductive circuits.Compensation can be effected in this caseusing a parallel capacitor.

With a suitably designed ballast it is pos-sible to operate two fluorescent lamps in series; this type of circuit is known as atandem circuit.

2.4.3 Radio interference suppressionand limiting other interference

Discharge lamps and the control gearthey require may give rise to various disturbance factors in both the supplynetwork and their environment.

This consists primarily of radio interference,which is caused by ignition devices and by the discharge lamp itself. Radiointerference can be suppressed by the use of suitably rated radio-interferencecapacitors.

Depending on their application con-trol gear and luminaires must meet certain minimum requirements with regardto radio interference (in Germany, Limit-ing Value Category B, VDE 0875, for example) and bear the seal of approval.Retroactive effects on the supply networkdue to harmonic oscillations have to be below stated minimum values (VDE 0712).

In the hospital environment, for example,the operation of ECG and EEG equipmentmay suffer interference from electric and magnetic fields induced by lightinginstallations – particularly by cabling, ballasts and transformers. For this reasonthere are special regulations (VDE 0107)for electrical installations in doctors’practices, hospitals and similar environ-ments.

Audio frequency energy control devicessuch as those that control night storageheaters and street lighting systems maycause interference from ballasts with parallel compensation. To avoid interferenceof this kind specially designed inductiveballasts can be wired in series with thecompensating capacitors.

67

Circuit diagrams forfluorescent lamps.Compensating circuit:power factor correc-tion by a capacitor inparallel (above).

Capacitive circuit: power factor is over-compensated by a se-ries capacitor (centre).

Twin-start circuit:combination of a non-compensated and an over-compensated circuit (below).

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N L

2.4 Control gear and control equipment2.4.4 Transformers

2.4.4 Transformers for low-voltage installations

In addition to ballasts and ignition devicesfor discharge lamps low-voltage in-stallations also require transformers as partof their control gear.

The low voltage required for such instal-lations, generally below 42 V (mostly 6, 12or 24 V) is taken from the mains voltageusing transformers. Transformers may bean integral part of the luminaire or may be installed separately and supply one ormore luminaires.

Transformers form an interface betweenmains voltage and low voltage, for whichcertain safety regulations apply. To gua-rantee that a low-voltage installation isnever subject to mains voltage, in the case of technical faults, in Germany forexample, safety transformers compliant withVDE 0551 must be used.

If transformers are mounted on in-flammable surfaces, they are required –as are luminaires – to bear an additionalM or M M symbol. These transformerscontain a thermal protection switch,which ensures that they do not overheat.

Transformers for low-voltage installa-tions must have fuses that can handle primary voltage (230 V). Slow-blow fusesare used for this, as currents up to 20 times above the rated current can occurwhen the lamp is switched on.

It must be noted that significant voltagedrops may occur in the connecting cableswhen dealing with low-voltage installa-tions. This is due to the high current values that occur with low voltages. Thiscan be compensated for, if appropriate cable diameters are used and the connec-tions are kept short; many transformershave both primary and secondary voltagetapping devices, which means that in the case of longer connection cables, exces-sive voltage drop can be avoided.

Electronic transformers are comparable toelectronic ballasts from the point of viewof their properties and functions: in parti-cular, the way they operate at high frequencies, the fact that they are smallerand lighter, and that they allow low power loss. Electronic transformers supplyvoltage that is to a large extent indepen-dent of the load. They are therefore suita-ble for handling small partial loads. As with electronic ballasts, d.c. operationfor emergency lighting is also possible. Electronic transformers are also more expensive than conventional transformers.

68

Fluorescent lamp cir-cuits. Tandem circuit:operation of two lampsconnected in series to one ballast (parallelcompensation).

Circuit diagrams forfluorescent lamps. Ope-ration on an electronicballast: starter andcompensating capacitorare not required. Singlelamp (above) and twin-lamp circuit (below).

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20

15

10

5

20 50 100 150 300 600 Pn (W)

Pv/Pn (%) OpencircuitFull load

20

15

10

5

20 50 100 150 300 600 Pn (W)

Pv/Pn (%) Fullload

2.4 Control gear and control equipment2.4.4 Transformers

69

Comparison of sizes oftransformers for low-voltage installations:600 W safety transfor-mer (above) and 100 Wversion (centre), 100 Welectronic transformer(below).

Relative power loss(PV/Pn) of transformersof varying rated powerPn in the case of stan-dard safety transformers(above) and electronictransformers (below).Data provided for opencircuit and full-loadoperation.

Rated power (Pn),weight (Wt.) and dimensions (l, w, h) of standard safetytransformers (above)and electronic transformers (below).

Pn (W) Wt. (kg) l (mm) w (mm) h (mm)20 0.5 120 56 5050 1.0 155 56 50100 1.8 210 56 50150 2.6 220 90 90300 5.5 290 150 130600 9.2 310 150 130

Pn (W) Wt. (kg) l (mm) w (mm) h (mm)50 0.2 155 45 30100 0.2 155 45 30

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230/U

230/U

230/U

PI2

A2

l1A1

¤ U2U

l1

l2

¤ U1¤ U

0,1

0,2

10 20 30 40 50 60P (W)

¤U (V/m)0,75 1,5 4,02,5 6,0 10

16

25

A (mm2)

120 240 360 480 600 720I (A)

2.4 Control gear and control equipment2.4.4 Transformers

70

Low-voltage installa-tion with individualtransformers. The wiringfrom transformer to luminaire is as short aspossible to keep voltagedrop to a minimum;the transformer mayalso be an integral partof the luminaire.

Low-voltage installa-tion with a singletransformer. Star-shaped wiring to en-sure the same wiringlengths between trans-former and fixtures:this guarantees that all lamps receive thesame applied voltage.

Limiting current I ofmulti-core conductorswith diameter A.

Outer diameter d ofsheathed cables of va-rious cable diameters Awith number n of cores.

The overall voltagedrop ¤U of a low-voltage installationwith a star-shaped wi-ring layout and singletransformer is a resultof the sum of the indi-vidual voltage drops

¤U1 + ¤U2. Individualvoltage drops are calculated according to the set formula,whereby l1 is the resultof all lamps 4P/U and I2of P/U.

Voltage drop ¤U per 1 m of cable in relationto current I and lamppower P for variouscable diameters A. Applies to 12 V installa-tions.

Voltage drop ¤U forcopper cable, dependingon current, length and diameter of cable.

A (mm2) I (A)0.75 121.0 151.5 182.5 264.0 346.0 4410.0 6116.0 8225.0 108

A (mm2) n d (mm)1.5 2 10

3 105 11

2.5 2 113 115 13

4.0 3 135 15

¤U = 0.035 . I . lA

[¤U] = V[I] = A[l] = m[A] = mm2

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2.4 Control gear and control equipment2.4.5 Controlling brightness

2.4.5 Controlling brightness

There are a number of applications where itis practical to not only be able to switch alighting installation or individual groups of luminaires on and off, but also to controltheir brightness. This means that thelighting can be adjusted to suit the use of the space and the ambient conditions;there is also a consider-able saving inenergy due to the virtually loss-free lea-ding edge dimmers. The ways and meansof controlling brightness largely dependson the type of light source installed.

2.4.5.1 Incandescent lamps and halogenlamps

Conventional incandescent lamps and ha-logen lamps for mains voltage are the easiest light sources to dim. Simple leadingedge dimmers are all that are required to control the brightness of these sources.

Incandescent lamps can be dimmedalmost 100 per cent. A slight reduction inoperating current results in considerablechanges in the characteristics of the lightsource; the luminous flux reduces drama-tically, lamp life increases considerably and there is a colour shift to the warmercolours of the spectrum. As we are familiarwith this gradual changing of colour temperature through natural phenomena(sunset, a fire burning out), we find thechange of luminous colour pleasant whenincandescent lamps are dimmed.

2.4.5.2 Low-voltage halogen lamps

Low-voltage halogen lamps behave in asimilar way to conventional incandescentlamps when dimmed. The reciprocal inter-action of dimmer and transformer meansthat these control gear components aresubject to increased stress. Conventionaldimmers can, therefore, not be applied in this case. Special dimmers for low-voltageinstallations are required. The transformersused must also be approved as compatiblewith dimming gear and equipped with fuses that are designed to cope with thehigh starting current. Dimming is basicallyeffected by controlling mains voltage.Conventional dimmers can sometimes beused together with electronic transformers,some makes still require specially adapteddimmers.

2.4.5.3 Fluorescent lamps

The brightness of fluorescent lamps can alsobe controlled, but the dimming behaviourof fluorescent lamps is considerably different to that of incandescent lamps.

At this stage it should be noted thatthere is a virtual linear correlation of lampcurrent and luminous flux.Whereas the luminous flux of an incandescent lamp is

reduced to approx. 50 % at a decrease inlamp current of 10 %, to attain this level of dimming in fluorescent lamps the lampcurrent also has to be reduced by 50 %.Fluorescent lamps do not change their lu-minous colour when dimmed.

Special dimmers are required to con-trol the brightness of fluorescent lamps.Some fluorescent lamp dimmers do not allow dimming to low illuminance levels,however. This must be taken into accountin lecture halls, for example, where especially low dimming levels are requiredwhen slides and videos are shown.

Much of the dimming equipmentavailable for fluorescent lamps requires anadditional fourth conductor for the heating of the electrodes. Such systemscannot be used for fluorescent lamps thatare operated on power tracks, as standardtracks only have three circuits.

During the dimming process the cablesbetween the dimmer and the luminaire are subject to a considerable load of idlecurrent that cannot be compensated,since the installation can only be com-pensated from outside the dimmed circuit.This idle current must be taken intoaccount when dimensioning cables andcontrol gear.

Controlling the brightness of fluorescentlamps can be effected in different ways, depending on the type of lamp, ballastand dimmer used.

26 mm lamps operated on inductive bal-lasts require a heating transformerwith an electronic starter. Special electronicballasts can also be used for controllingthe brightness of 26 mm fluorescent lamps.They usually have to be supplied togetherwith suitable dimmers, or they can be operated with all other kinds of dimmersdesigned for use with fluorescent lamps.In addition, each fixture has to be equipped with a special filter choke or aconventional ballast designed to function as a filter choke. Some of thesemeans of controlling brightness require a three-wire connection, which makesthem suitable for application with tracksystems. When electronic ballasts are usedthere are none of the disturbing flicker effects that can occur when dimming atmains frequency. The way the dimming of 38 mm lampsoperated on inductive ballasts was formerly effected is no longer of any realsignificance. It required special lampswith ignition aids and heating transformersfor the permanent heating of the lampelectrodes.

71

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1 2 EVG

3 4 5

2.4 Control gear and control equipment2.4.6 Remote control2.4.7 Lighting control systems

2.4.5.4 Compact fluorescent lamps

Compact fluorescent lamps with a two-pinbase (integral starter) cannot be dimmed.Lamp types with four-pin bases are dimmed in the same way as conventional26 mm fluorescent lamps.

2.4.5.5 Other discharge lamps

As a rule high-pressure discharge lamps andlow-pressure sodium lamps are not dimmed, because it cannot be guaranteedthat the lamps will continue to burn con-sistently and dimming has a deterioratingeffect on the properties of the lamp.

2.4.6 Remote control

Remote control systems provide the op-portunity to control individual luminairesor circuits with the aid of a remote controlunit. Receivers have to be installed in the fixtures, lighting installations or dis-tributor boxes; these receivers switch or dim the fixtures they are connected tothrough an infrared signal. By coding signals it is possible to address a numberof fixtures or circuits separately. Remotecontrol systems can be used to controlthe lighting from any position withina space using a hand-held controller.The great advantage of such systems isthe fact that an individual circuit can besubdivided into several, separately controll-able units.There are special receivers available foroperation on tracks. These receivers can control all the track circuits. This meansthat – especially in the case of old buildings with only one circuit availableper room – it is possible to install differen-tiated lighting into a room easily andeconomically.

2.4.7 Lighting control systems

The task of a lighting installation is tocreate optimum visual conditions for anyparticular situation. Good lighting must enable the users of the space to performthe necessary visual tasks and move safelyfrom room to room. Furthermore, it shouldalso take into consideration the aestheticandpsychological effects of the lighting, i.e.provide an aid for orientation, accentuatearchitectural structures and support the architectural statement. One only hasto consider the simplest of lighting tasksto understand that the requirements cannot be fulfilled by one lighting conceptalone. The lighting has to be adjusted to meet the changing conditions in theenvironment – the conditions for nightlighting are different from the supple-mentary lighting required during the day.The requirements of a lighting installationare substantially different when it comes to the uses of the space, e.g. the change of

72

Track system with 3-channel remote con-trol. The receiver can be controlled via a manual device or a wall-mounted unit.

Example of the remotecontrol of a three-circuit track system byswitching and dimming of individualcircuits.

Diagram showing a programmablelighting control system. Preset panels(1) installed in the respective spaceallows pre-programmed light scenes to be called up. The switching and dimming sequences for the

specific light scenes are programmedand saved in the central control unit(2). Various dimming modules allowthe dimming of incandescent lamps(3), low-voltage halogen lamps (4)and fluorescent lamps (5).

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6

2

7

3

8

4

9

5

0

?

C

F1

F3

F2

F4

ON

OFF

1

4

2

5

3

6

ON

OFF

12

2.4 Control gear and control equipment2.4.7 Lighting control systems

events in a multi-purpose hall, the changeof exhibitions in a museum or even theway a standard office space can be trans-formed into a conference room.

To meet such changing requirements a lighting installation has to be able to bedimmed and switched in a variety of waysto create different light scenes. The pre-requisite is that luminaires or groups ofluminaires can be switched separately andtheir brightness controlled, so that the illuminance level and lighting quality in specific areas of the space can be adju-sted to particular situations. The result is an optimum pattern of switched lumi-naires and brightness levels, a light scenethat complies with the use of the room or creates specific ambient conditions. Iflarge numbers of luminaires are to be controlled accurately, it is a good idea tostore the light scenes electronically so that any scene may be called up as required.

The main task of a lighting control systemis to store a series of light scenes – eachcomprising the switching and dimmingstatus required for the various circuits –and to call them up when required. Usinga programmed lighting control system it is, however, possible to create morecomplex processes than a simple changeof scenes. A change of scene can be pro-grammed to be effected instantaneouslyor in the form of a seamless transition,for example. It is also possible to raise or lower the overall brightness level of alight scene without re-programming.

The transition from one scene to ano-ther can be effected manually using a preset panel. It is also possible to have achange of scenes controlled automati-cally. In this case the lighting control isusually dependent on the amount of day-light available or what day of the week it is and what time of day/night.

Due to the miniaturisation of electroniccomponents lighting control systems areso compact that some of them can be installed in existing distribution boxes orfuse boxes, although large-scale systemswill require their own cabinet. Lightingcontrol systems consist of a central con-trol unit for digital storage and control, a series of load modules (dimmers or relays), which are each allocated to a circuit, and one or more preset panels.Depending on the application, other modules for time or daylight-related controland for the lighting control in a number of different spaces are required. Via specialswitching arrangements or by incor-porating lighting control systems intobuilding management programmeslighting control systems can also controland supervise other technical equipmentbesides the lighting (e.g. sun-blinds or pro-jection screens).

2.4.7.1 Lighting control systems for theatrical effects

Unlike stage lighting whose task it is tocreate illusions, architectural lightingconcentrates on human visual re-quirements and on defining our real sur-roundings. In spite of this basic differencesome stage lighting methods have beenadopted in the field of architecturallighting. Lighting concepts that comprisetheatrical effects are becoming increa-singly popular. These include stark contrasts between light and dark, the application of coloured light – using spot-lights and colour filters, contour lightingusing coloured neon tubes – and goboprojections.

Besides creating specific effects onstage it is the way that stage lightingchanges that plays a decisive role; a change of scenes in this case no longerserves as a method for adjusting to existing requirements, but becomes a design element in its own right. Changesin the lighting are not merely related to switching groups of lights on and offand changing the level of brightness; they also include distribution characteristics,beam direction and colour.

Stage lighting control systems there-fore have to meet considerably morestringent requirements than conventionallighting control systems. With the increa-sing trend to apply theatrical lightingeffects in architectural spaces architectu-ral lighting designers now require lightingcontrol systems that are not only ableto switch and dim fixtures, but are alsoable to change their position, colour and distribution characteristics.

73

Example of a pre-programmable lightingcontrol system: presetpanel (centre) for 6scenes with On/Offswitches for controllingthe brightness of theoverall installation.Central control unitwith LCD display(above). Circuit module(below) with pro-grammed address andOn/Off switches for testing purposes.

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100

80

60

40

20

300 500 700E (lx)

100 900

P (%)

0,5

300 500 700E (lx)

100 900

S

1,0

1,5

2,0

2,5

3,0

0.5

30 50 70Age (a)

10 90

S

1.0

1.5

2.0

2.5

3.0

2.5 Light2.5.1 Quantity of light2.5

Up to now visual perception and the pro-duction or generation of light have beentreated as two separate topics. We will nowconsider the area where light and perception meet – and describe the quali-ties and features of light. The intention is to show how specific qualities of lightcreate different perceptual conditions andthereby influence and control human perception. Illuminance plays as great a part as light distribution, beam direction,the colour quality of a lighting installationor glare limitation.

A comprehensive set of regulations existfor workplaces which define the optimumlighting conditions for specific visual tasksto ensure that visual tasks can be performed correctly and without causing fatigue. The standards only relate to establishing good working practice regar-ding working conditions. Broader con-cepts are required to take into considerationthe architectural and psychological requirements of the visual environment.

2.5.1 Quantity of light

The basis for any lighting installation is thequantity of light available for a specific visual task in a given situation. Every-oneknows that light is a prerequisite for visual perception. Up to around a hundredyears ago we were dependent on the amount of light available throughconstantly changing daylight conditionsor weak artificial light sources, such ascandles or oil lamps. Only with the development of gas light and electric lightdid it become possible to produce sufficient amounts of light and thus toactively control lighting conditions.

There then followed the evaluation ofthe amount of light that was appropriate in each situation, establishing the upperand lower illuminance and luminance limits in specific situations. Much investi-gation went into lighting conditions in the working environment to establish illu-minance levels for optimum visual perfor-mance. By visual performance we meanthe ability to perceive and identify objectsor details, i.e. visual tasks with given contrast between the object viewed andthe surrounding area.

Visual performance generally improves whenthe illuminance level is increased. This effect improves more slowly from 1000 luxupwards, however, and decreases rapidlyat extremely high illuminance levels dueto glare effects.

In the case of simple visual tasks ade-quate visual performance can be attainedat low illuminance levels, whereas com-plex visual tasks require high illuminance levels. 20 lux is the threshold value at which a person’s facial features can be recognised. At least 200 lux is requiredfor continuous work, whereas complicated

Light Qualities and features

74

Influence of illumi-nance E on the relativevisual performance Pfor simple (upper curve)and complicated visualtasks (lower curve).

Influence of illumi-nance E on the visualacuity S of normal-sighted observers.

Visual acuity S in relation to age(average values).

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1

2

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S

å

2.5 Light2.5.1 Quantity of light

visual tasks require up to 2000 lux, in spe-cial cases, e.g. in operating theatres, up to10000 lux. The preferred illuminance levelat the workplace ranges between 1000 and2000 lux.

International guidelines for illuminancelevels range in values from 20 to 2000 luxand are therefore within the above-mentioned framework. The recommendedilluminance levels are mainly a consequenceof the degree of difficulty of the visualtask in contrast to the immediate environ-ment, whereby extremely detailed visualtasks, where there is little contrast to the surrounding area, require the highestilluminance levels.

Following a set of fixed rules for overallilluminance levels as laid down in thestandards for the lighting of workplaces,which is generally what lighting designamounts to in practice, includes minimalconsideration regarding actual percep-tion. It is not the luminous flux falling ona given surface – illuminance – that produces an image in the eye. It is the lightthat is emitted, transmitted or reflected by the surfaces. The image on the retina iscreated entirely by the luminance patternof the perceived objects, in the combinationof light and object.

Recommendations have also been laid downfor luminance levels, that is to say formaximum luminance contrasts betweenvisual task and surrounding area. Likewisefor absolute luminances that are not tobe exceeded, for example of luminous ceilings or luminaires in spaces equippedwith VDT workstations. The object is again is to optimise visual performance atthe workplace.

In addition to these guidelines there isalso a set of general recommendations for luminance distribution in the entirespace. It is assumed that a space with low luminance contrasts will appear to be monotonous and uninteresting and a space with stark contrasts restless and irritating.

For some time now more systematicapproaches to comprehensive lighting de-sign have been made based on the resultsof research on luminance distribution. InWaldram’s “designed appearance” conceptor Bartenbach’s idea of “stable perception”,in particular, there have been attempts to control the visual appearance of the overall environment (mood, atmosphere)through the purposeful arrangement ofluminances.

Any attempt to design a lighting installation based on quantitative data isbound to lead to problems. This applies to overall illuminance stipulations and luminance scales as well as to sets of givenluminance patterns.

Visual perception is a process whichallows us to gain information about objects in the world around us using the medium of light. A process that is there-

75

The Landolt ring fordetermining visualacuity. The visual taskis to determine the position of the openingin the ring. The gapis 1/5 of the ring’s dia-meter.

Table for determiningthe reader’s visualacuity S from a dis-tance of 2 m.

Typical illuminance levels E in interior spaces.

Recommended illumi-nance levels E accor-ding to the CIE for various activities.

The angle of vision åis calculated from thewidth of the openingof the smallest detec-table Landolt ring andthe distance of theviewer from the image.Visual acuity S is itsreciprocal value.A visual acuity of 1 is recorded when the gapin the ring can be re-cognised at an angle ofvision of å = 1' (1/60°).

E (lx)20 Minimum value in interior spaces, excluding working areas

Illuminance level required for recognising facial features200 Minimum illuminance for workplaces in continuous use2 000 Maximum illuminance at standard workplaces20 000 Illuminance level for special visual tasks

e.g. in operating theatres

E (lx)20–50 Paths and working areas outdoors50–100 Orientation in short-stay spaces 100–200 Workrooms that are not in continuous use200–500 Simple visual tasks300–750 Visual tasks of average degree of difficulty500–1000 Difficult visual tasks, e.g. office work750–1000 Complicated visual tasks, e.g. precision assembly work1000–2000 Extremely complicated visual tasks,

e.g. inspection and control> 2000 Additional lighting for difficult and complicated tasks

S = 1å

[å] = min

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2.5 Light2.5.2 Diffuse and directed light

fore basically influenced by three factors:light, object and perceiving being. A design concept that is restricted to fixed illuminance criteria is only concernedwith the aspect of the light. Illuminanceis therefore inadequate as a basis for predicting visual effect, especially as it isnot itself perceptible.

When planning luminance distributionit is not only the light that is taken into consideration, but the correlation of the light with the objects in the space.Luminance is the basis of the brightnesswe perceive, which means that the perceptual process is taken into account,at least up to the moment an image isprojected onto the retina.

But luminance and luminance distributiondo not provide an adequate basis for theplanning of visual impressions – attentionhas yet to be paid to the perceiving indi-vidual. The pattern of luminances projectedonto the retina is not the end product, but simply forms the basis for a complexprocess at the end of which is the image we actually see. This involves innumerableaspects: laws of gestalt, constancy phenomena, expectations and the infor-mation content of the object that is beingperceived.

The aim of perception is not just toregister luminous phenomena, but to gaininformation about the environment. It isnot the luminances produced by an accumulation of objects that are interesting,but rather the information about thequality of these objects and about the lighting conditions under which thisquality can be perceived.

This is why the image that we actuallyperceive is not identical to the pattern of luminances on the retina, although it is based on this luminance pattern. A white body has different luminancequalities depending on the lighting situation. Evenso, it is always perceived asbeing uniformly white, because thelighting situation is registered and takeninto account when the image is beingprocessed. The formation of shadows on a spatial body – its luminance pattern – is not interpreted as being unevenly lit,but as a feature of a three-dimensionalform. In both cases the characteristics of the object and the type of lighting areinterpreted from the perceived luminancepattern simultaneously. These simple exam-ples are clear evidence of the importantpart psychological processing has to playin the creation of the final perceivedimage.

When a lighting design concept purpose-fully strives to achieve specific visual effects it must involve all factors relatedto the perceptual process. Lighting designcannot be restricted to the observance of illuminance or luminance levels, of lightand object alone, even when this ap-proach effectively results in optimum per-

ceptual conditions at workplaces, for ex-ample. Apart from considering the qualities of the light to be applied lightingdesign must – as an integral part of the design of the environment – also takeinto account the interaction of lightsource, object and perceiver, as governedby the laws of perceptual psychology, ineach respective situation.

2.5.2 Diffuse light and directed light

Having dealt with light quantity, conside-ration must be given to the quality oflight, the difference between diffuse lightand directed light being one of the mostimportant aspects. We are familiar withthese different forms of light through oureveryday experience with daylight – direct sunlight when the sky is clear anddiffuse light when the sky is overcast.Characteristic qualities are the uniform,almost shadowless light we experience under an overcast sky, in contrast to thedramatic interplay of light and shade inbright sunlight.

Diffuse light is produced by extensive areasthat emit light. These may be extensive,flat surfaces, such as the sky in the day-time, or, in the field of artificial lighting,luminous ceilings. In interior spaces diffuse light can also be reflected from illuminated ceilings and walls. This produces very uniform, soft lighting, whichilluminates the entire space and makesobjects visible, but produces reduced shadows or reflections.

Directed light is emitted from pointlight sources. In the case of daylight this isthe sun, in artificial lighting compact lightsources. The essential properties of directedlight are the production of shadows on objects and structured surfaces, and reflections on specular objects. These effects are particularly noticeable when thegeneral lighting consists of only a smallportion of diffuse light. Daylight, for example, has a more or less fixed ratio of sunlight to sky light (directed light todiffuse light) of 5:1 to 10:1.

In interior spaces, on the other hand,we can determine the ratio of directed and diffuse light we require or prefer. Theportion of diffuse light decreases whenceiling and walls receive too little light, orwhen the light falling on a surface is absorbed to a large extent by the low re-flectance of the environment. This can be exploited for dramatic effects through accent lighting. This technique is often applied for the presentation of objects, butis only used in architectural lighting whenthe concept intends to create a dramaticspatial effect.

Directed light not only produces shadowsand reflections; it opens up new horizonsfor the lighting designer because of thechoice of beam angles and aiming directions

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2.5 Light2.5.2 Diffuse and directed light

that he has at his disposal. Whereas thelight emitted by diffuse or exposed lightsources always has an effect on the entirespace, in the case of tightly controlledlight, the effect of the light relates directlyto the position of the luminaire.

Here lies one of the most progressiveaspects of lighting technology. Whereas in the era of the candle and the oil lampthe light was bound to the immediate vicinity of the luminaire, it is now possibleto use light in other parts of the space at any distance from where the light sourceis located. It is possible to use lighting effects at specific illuminance levels onexactly defined areas from practically anylocation within a space. This means that a space can be purposefully lit and thelighting modulated. The relative local illuminance level can be adjusted to suitthe significance of a particular part of a space and the perceptual information itcontains.

2.5.2.1 Modelling

Another basic feature of the world aroundus, and one that we take absolutely forgranted, is its three-dimensional quality.One essential objective regarding visualperception must therefore be to provideinformation about this aspect of our environment. Three-dimensionality compri-ses a number of individual areas, from theextension of the space around us to the location and orientation of objects withinthe space, down to their spatial form andsurface structure.

Perception of the three-dimensional cha-racter of our environment involves pro-cesses that relate to our physiology andperceptual psychology. The shaping of ourenvironment through light and shade is of prime importance for our perception ofspatial forms and surface structures. Modelling is primarily effected using directedlight. This has been referred to, but the significance for human perception mustbe analysed.

If we view a sphere under completelydiffuse light we cannot perceive its spatialform. It appears to be no more than a circular area. Only when directed light fallson the sphere – i.e. when shadows arecreated, can we recognise its spatial quality.The same applies to the way we perceivesurface structures. These are difficult torecognise under diffuse light. The textureof a surface only stands out when light isdirected onto the surface at an angle andproduces shadows.

Only through directed light are we able to gain information about the three-dimensional character of objects. Just asit is impossible for us to retrieve this in-formation when there is no directed lightat all, too much shaping can conceal information. This happens when intensely

77

Perception of three-dimensional forms andsurface structures underdifferent lighting condi-tions.Directed light producespronounced shadowsand strong shaping effects. Forms and sur-face structures are accentuated, while details can be concealedby the shadows.

Lighting that consists ofboth diffuse and direc-ted lighting producessoft shadows. Forms andsurface structures canbe recognised clearly.There are no disturbingshadows.

Diffuse lighting producesnegligible shadowing.Shapes and surface struc-tures are poorly recognis-able.

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2.5 Light2.5.2 Diffuse and directed light

directed light casts such stark shadowsthat parts of an object are concealed bythe darkness.

The task of lighting design is there-fore to create a suitable ratio of diffuse lightto directed light to meet the requirementsof each individual situation. Specific visual tasks, where the spatial quality orthe surface structure is of prime im-portance, require lighting that emphasisesshapes and forms. Only in situationswhere spatial quality and surface structureare of no importance, or if they are disturbing factors, can completely diffuselighting be used.

As a rule suitable proportions of dif-fuse light and directed light are required.Well balanced portions provide goodoverall visibility of the environment andsimultaneously allow spatial appreciationand vivid perception of the objects.

In some standards for workplacelighting there is a criterion for the model-ling effect of a lighting installation. It is referred to as the modelling factor, whichis defined as the ratio of cylindrical illu-minance to horizontal illuminance.

When planning the application of direc-ted and diffuse light it is advisable to rely on our fundamental experience ofdaylight with regard to the direction andcolour of the light. Direct sunlight eithercomes from above or from the side, butnever from below. The colour of sunlightis clearly warmer than that of diffuse skylight. Consequently, lighting that compri-ses directed light falling diagonally fromabove with a lower colour temperaturethan the diffuse general lighting will befelt to be natural. It is, of course, possibleto apply light from other directions andwith other colour temperature combinati-ons, but this will lead to effects that areespecially striking or strange.

2.5.2.2 Brilliance

Another feature of directed light along-side its modelling effect is brilliance. Brilliance is produced by compact, pointlight sources and is most effective when ap-plied with an extremely low proportion of diffuse light. The light source itself will be seen as a brilliant point of light. A goodexample of this is the effect of a candle-light in evening light. Objects that refractthis light are perceived as specular, e.g. illuminated glass, polished gems or crystalchandeliers. Brilliance is also producedwhen light falls on highly glossy surfaces,such as porcelain, glass, paint or varnish,polished metal or wet materials.

Since sparkling effects are producedby reflections or refraction, they are not primarily dependent on the amount oflight applied, but mostly on the luminousintensity of the light source. A very com-pact light source (e.g. a low-voltage halo-gen lamp) can create reflections of far

greater brilliance than a less compactlamp of greater luminous power.

Brilliance can be a means of attracting attention to the light source, lending a space an interesting, lively character.When applied to the lighting of objectsbrilliance accentuates their spatial qualityand surface structure – similar to model-ling – because sparkling effects are mainlyevident along edges and around the cur-ves on shiny objects.

Accentuating form and surface structureusing brilliance enhances the quality of the illuminated objects and their surroundings. Sparkling effects are in factgenerally used in practice to make objectsor spaces more interesting and presti-gious. If an environment – a festival hall,a church or a lobby – is to appear especi-ally festive, this can be achieved by using sparkling light sources: candlelightor low-voltage halogen lamps.

Directed light can also be applied withsparkling effect for the presentation of specific objects – making them appearmore precious. This applies above all for the presentation of refractive or shinymaterials, i.e. glass, ceramics, paint or metal. Brilliance is effective because it attracts our attention with the promise ofinformation content. The information wereceive may only be that there is a spark-ling light source. But it may also be in-formation regarding the type and quality of a surface, through the geometry andsymmetry of the reflections.The question still has to be raised, how-ever, whether the information our atten-tion has been drawn to is really of interest in the particular situation. If this isthe case, we will accept the sparkling lightas pleasant and interesting. It will createthe feeling that the object of perception, or the overall environment, is exclusive.

If the brilliance possesses no infor-mative value, then it is found to be distur-bing. Disturbing brilliance is referred to asglare. This applies in particular when it arrises as reflected glare. In offices, reflec-tions on clear plastic sleeves, computermonitors or glossy paper are not interpre-ted as information (brilliance), but as disturbing glare, disturbing as it is felt thatthe information we require is being con-cealed behind the reflections.

78

It is possible to createuniform lighting in a space by using severalpoint light sources. Due to the fact that eachlight beam is directed,objects within the space will cast multiple shadows.

In the case of uniformlighting with diffuselight the shadows aresofter and far less distinct.

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2

3

2.5 Light2.5.3 Glare

2.5.3 Glare

An essential feature of good lighting is theextent to which glare is limited. There are two aspects to glare: the objective de-preciation of visual performance, and thesubjective disturbance felt by individualsthrough excessive luminance levels orstark contrasts in luminance levels withinthe field of vision.

In the case of objective depreciation in visual performance the term physiologicalglare is applied. In this case the light froma glare source superposes the luminancepattern of the visual task, thereby reducingvisibility. The reason for this super-imposition of the luminous intensities ofvisual task and glare source may be the direct overlay of the images on the retina.Superimposition of scattered or distur-bing light, which arises through the dis-persion of the light from the glare sourcewithin the eye, is often enough to re-duce visual performance. The degree oflight scattering depends primarily on the opacity of the inner eye. The latter increases with age and is the reason why older people are considerably more sensitive to glare.

The most extreme case of physiologi-cal glare is disability glare. This ariseswhen luminance levels of more than 104

cd/m2 are evident in the field of vision,e.g. when we look directly at artificiallight sources or at the sun. Disability glaredoes not depend upon the luminancecontrast in the environment. It cannot beeliminated by increasing the luminancelevel. Disability glare seldom presents a problem in architectural lighting. Here it is more a question of relative glare, whereby the reduction of visual perfor-mance is not caused by extreme luminan-ces, but by high luminance contrasts within the field of vision.

If the glare source is not the cause of areduction in visual performance, but merely a subjective interference factorthe term discomfort glare is used. Dis-comfort glare occurs when an individualis involuntarily or unconsciously dis-tracted by high luminance levels withinthe field of vision. The person's gaze is constantly being drawn away from the visual task to the glare source, althoughthis area of increased brightness fails toprovide the expected information. A glaresource is also frequently referred to as visual noise, and as such can be comparedwith a disturbing sound that continually attracts our attention and undermines ourperception.

Repeatedly having to adjust to variousbrightness levels and the distance be-tween the visual task and the glare sourceeventually leads to eye strain, which isconsidered to be unpleasant or even pain-ful. Although visual performance may objectively remain unchanged, discomfort

glare can lead to a high degree of unease,which in turn will have an effect on the person's overall performance at his/herworkplace.

In contrast to disability glare, whichcan be explained irrespective of the speci-fic situation as the exceeding of given luminance or luminance contrast values, di-scomfort glare is a problem that concernsthe processing of information, which cannot be described out of context – theinformation content of the visual environ-ment and the perceptual information we require in a given situation. Althoughthere may be considerable luminancecontrasts occurring within the field of vision, discomfort glare does not becomea problem, if these contrasts are expectedand provide valuable information, e.g. the sparkling light of a crystal chandelieror an appealing view out of a window. On the other hand, even slight differencesin luminance levels can give rise to discomfort glare, if these contrasts overlaymore important information and them-selves provide no information; e.g. in thecase of reflections on glossy paper, whenwe look at a uniformly overcast sky or at a luminous ceiling. Disability and discom-fort glare both take two forms. The first is direct glare, where the glare source itself is visible in the field of vision of the visualtask. In this case the degree of glare depends mainly on the luminous intensityof the glare source, its luminance contrastto the visual task, its size and proximity to the visual task.

The second form of glare is reflectedglare, in which the glare source is reflectedby the visual task or its ambient field. This form of glare depends on the above-mentioned factors and the specular qua-lity and position of the reflecting surface.

Discomfort glare caused by reflectedlight creates considerable problems forpersons reading texts printed on glossypaper or working at computer monitors,as the eye is continually straining to accommodate to the visual task, which isat close range, and the distraction of thereflected glare source, which is located atsome distance away.

The evaluation of luminances and lumi-nance contrasts that may lead to unwantedglare is predominantly dependent on thetype of environment and the requirementthat the lighting aims to fulfil. The rulesthat govern a festive or theatrical environ-ment are entirely different from those forworkplaces; what may be desired brilliance in one case may be con-sidered to be unwanted glare in another.The predominant directions of view alsoplay a significant role; lighting that maybe glare-free for a person sitting uprightin a chair may constitute glare if that sameperson leans back.

There is a set of formalised rules thatapply to glare limitation in the field oflighting at workplaces; as a rule, they are

79

In the case of physio-logical glare the retinalimage of the objectbeing viewed (1) is superimposed by lumi-nances that occur in the eye from the dis-persion (2) of the lightproduced by a glaresource (3).

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3 2 1

2

3

©G

å

2.5 Light2.5.3 Glare

based on a person working seated at a deskwith louvred luminaires providing the lighting. From the height of the sit-ting position and the preferred directionof view areas can be defined in whichlight sources will tend to produce the mostglare. Apart from glare through windowsglare is mainly produced by luminaires located in specific parts of the ceiling.

In the case of direct glare this is thearea of ceiling in front of the seated person and perceived at angles lower than45°. In the case of reflected glare, the glare is caused predominantly by lumi-naires located in the ceiling area directly in front of the person. Reflected glare onVDTs, that is to say on practically verticalsurfaces, presents a special case. In thiscase glare is mainly caused by glaresources in the ceiling area behind the person.Glare can be minimised by reducing luminance contrasts – for example, byraising the ambient luminance or lowering the luminance of the glare source.Glare can also be avoided by suitably arranging the luminaire geometry.Continuous rows of louvred luminairesshould not be installed cross-wise to the direction of view, for example, butparallel to the direction of view and bet-ween the workplaces.

Suitable glare limitation can be achie-ved by the correct choice of luminaires.Especially developed reflectors can guarantee that luminaires positioned abovethe critical angle do not produce any unacceptable luminances. By installing luminaires that emit only minimal directlight downwards can also make a sub-stantial contribution towards limiting re-flected glare.

In Germany DIN 5035 is used for the evaluation of glare limitation at the work-place. It describes a specific process for checking that limiting values betweencomfort and direct glare are not exceeded.The luminance of the installed luminairesis determined at angles of 45°–85° andentered in a diagram. Depending on the rated illuminance, the type of luminairesand the required visual compfort thelighting installation aims to meet, luminance limiting curves can be drawn onthe diagram that are not to be exceededby the luminance curve stipulated for theluminaire installed.

In the case of direct glare there is thequantitative method of evaluatingluminance limiting curves. Reflected glarecan only be evaluated according to qualitative criteria, however. For reflectedglare in the case of horizontal reading,writing and drawing tasks there is a processthat describes the degree of reflectedglare in quantitative terms via the contrastrendition factor (CRF). The contrast rendi-tion factor in this case is defined as theratio of the luminance contrast inherent toa visual task under totally diffuse standard

80

With regard to glare adistinction is madebetween direct glare,caused primarily by luminaires (1), reflectedglare in the case of horizontal visualtasks (2) and reflectedglare in the case ofvertical visual tasks, e.g.at VDT workstations (3).

The luminance of luminaires that cause reflections on con-ventional computermonitors should not exceed 200 cd/m2

above a critical angle ©G.Normally ©G values lie between 50° and 60°.

Glare limitation at VDTworkstations: for areas with VDT work-stations a cut-offangle å of at least 30°is recommended.

Luminance levels ofwalls that produce reflections on monitorsshould not exceed 200 cd/m2 on average,or 400 cd/m2 as a maxi-mum. The reflection of windows on computer monitors should basically be avoided.

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85˚

45˚

CategoryA1

Mean illuminance (lx)10002000

7501500

5001000

–750

300500

55˚

85˚

75˚

65˚

L(cd/m2)103 2 3 4 5 6 8 104

55˚ 70˚

E = 500 lx ©�

1

2.5 Light2.5.3 Glare

lighting conditions to the luminancecontrast of the same visual task under the given lighting conditions.

The contrast rendition factor (CRF) isbased on a reflection standard comprisingone light (high reflectance) and one dark(low reflectance) ceramic disc with stan-dardised reflectance for various directionsand angles of illumination. For completelydiffuse lighting the reference contrast isknown.

The CRF can be measured in an actuallighting installation on the basis of the given reflection standard or calculatedon the basis of the reflectance data. The CRF is then classified into one of threeCRF categories.

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Minimum cut-off angleof luminaires with different light sources,in relation to the glare limitation category.

To evaluate direct glarethe luminance of the luminaires withinthe range 45° to 85°is considered.

Luminance limitingcurves (for luminaireswithout luminous sidepanels). They identifyvalues for average luminance L of the luminaire at angles ©between 45° and 85°,which are not to beexceeded by the lumi-naire in question forthe given mean illumi-nance and for the re-quired glare limitationcategory.

Example of how to applyglare limitation to an illuminance level of 500 Ix and category A.From the geometry of the space the viewingangle for the first luminaire is 55°, for thesecond luminaire 70°.The corresponding luminances can be readoff luminance curve1 inthe diagram.

The luminance curvedoes not exceed the limiting curve, the luminaire thereforemeets the require-ments laid down forglare limitation.

Lamp type Glare limitation categoryA B C DVery low High Average Low

Fluorescent lamp 20° 10° 0° 0°Compact fluorescent lamp 20° 15° 5° 0°High-pressure lamp, matt 30° 20° 10° 5°High-pressure lamp, clear 30° 30° 15° 10°Incandescent lamp, clear

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L O2

L 1

L 2

å

25˚

Viewpoint

115˚

25˚

35˚DIN A3

15˚

30˚45˚

2.5 Light2.5.3 Glare

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Contrast rendition fac-tor CRF is a criterionfor contrast perceptionat viewing angle å. CRF <1 indicates thatthe lighting has lostpart of its contrastrendering quality dueto reflections.CRF >1 indicates thatthe lighting situationexceeds the quality of the reference lightingwith regard to contrastrendition.

By projecting the fieldof vision onto the cei-ling surface it is possi-ble to define the areain which the luminairesmay have a negativeinfluence on contrastrendering. For the basicplanning of a lightinginstallation the CRFvalue is generally onlycalculated for the primary viewing angleof 25°.

Grid for calculating thecontrast rendition factor, taking as a basisan A3 format area of view at viewing pos-ition (1), 50 mm in frontof and 400 mm abovethe front edge of thearea under consideration.

Recommendations foraverage and minimumCRF values dependingon the type of visual taskand CRF rating.

Evaluating the contrastrendition factor (CRF): in the case of a comple-tely diffuse referencelighting situation (idealised representationof a light hemi-sphere,above left) the referencevalue for standard reflectanceaccording to Bruel + Kjaer is C0(above right).

In the case of an ac-tual lighting situation(below left) the con-trast value for standardreflectance with a viewing angle å is C(below right).

Visual task Contrast CRF CRF CRFrendering cat. av. value min. value

Predominantly glossy High 1 1.0 ≤ CRF ≥ 0.95Matt with a soft sheen Average 2 0.85 ≤ CRF < 1.0 ≥ 0.7Matt Low 3 0.7 ≤ CRF < 0.85 ≥ 0.5

C0 = L01 – L02L01

C = L1 – L2L1

CRF = = = L1 – L20,91 . L1

C0,91

CC0

C0 = 0,91

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0.26

0.34

0.42

0.50

0.58

0.720.32 0.48 0.640.40 0.56

50004000

3000

2000 K1600 K

Spectral colour loci

nw

x

y

tw

ww

2500 K3300 K

6000

8000

0.26

0.34

0.42

0.50

0.58

0.720.32 0.48 0.640.40 0.56

Spectral colour loci

x

y 565

580

600

620690–780

E

123

56

4A

D 65

y

0.2

0.4

0.6

0.8

0.2 0.4 0.6 0.8x

E

Blue

Blue-green

Green Yellow-green

Yellow

Orange

Red

Purple

Wavelength (nm)Spectral colour loci

Purpleboundary

0.1 0.3 0.5 0.7 0.9

0.1

0.3

0.5

0.7

0.9

380–410

480

490

520

540

560

570

600

590

690–780

620

2.5 Light2.5.4 Luminous colour and colour

rendering

2.5.4 Luminous colour and colour rendering

Apart from luminance, which is perceivedas brightness, the eye also registers animpression of colour based on the spectralcomposition of the perceived light. The light itself can also be seen as beingcoloured (luminous colour). Colour is, how-ever, also produced through the capacityof various materials to absorb specificspectral ranges, thereby changingthe spectral composition of the light whichthey reflect (object colour).

There are various systems by which coloursare described.

The Munsell system or the DIN colourchart arrange object colours according to brightness, hue and saturation, whichproduces a comprehensive colour atlas in the form of a three-dimensional matrix.Brightness is referred to in this case as the reflecting coefficient of an objectcolour; hue is the colour tone, and the term saturation refers to the degree ofcolour strength from pure colour to thenon-coloured grey scale.

In the CIE’s standard chromaticity dia-gram object colours and luminous colourare, however, not arranged according to a three-dimensional catalogue. They arecalculated or measured according to thespectral composition of the illuminant forluminous colours, or the reflectance or transmittance of the object for objectcolours, and presented in a continuoustwo-dimensional diagram. This systemdisregards brightness as a dimension, withthe result that only hue and saturation canbe determined using this diagram.

The CIE chromaticity diagram representsa plane that comprises all actual coloursand satisfies a number of other conditions.The plane is surrounded by a curved borderline, along which the colour loci ofthe saturated spectral colours lie. The point of lowest saturation is locatedin the centre of the plane, and is referredto as the white point. All degrees of satu-ration of a colour on the saturation scalecan now be found on the lines that run between the white point and the spectralcolour loci. Additive combinations of two colours also lie along the straight linesthat link the respective colour loci.

A curve can be drawn inside the colouredarea to show the luminous colour of a Planckian radiator (black body) at diffe-rent colour temperatures; this curve can be used to describe the luminous colourof incandescent lamps. To be able to describe the luminous colour of dischargelamps, a series of straight lines of correla-ted colour temperatures is entered on the graph, starting from the Planckian radiator curve. With the aid of this arrayof lines it is also possible to allocate luminous colours that are not present onthis curve to the colour temperature of a

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The CIE’s chromaticitydiagram. The spectrumlocus links the colourloci of all saturatedspectral colours. Thepurple boundary formsthe line between the long-wave and short-wave spectral range.The white point E marksthe point of least

saturation. The border-lines that separate the different colour re-gions fan out from thewhite point. The chromaticity of anyreal colour can bedefined using the x/ycoordinates in thechromaticity diagram.

Section of the chroma-ticity diagram with thecurve relating to thePlanckian radiator andthe series of straightlines marking the colourloci of the same correlated colour tem-perature between 1600and 10000 K. The ran-ges given are the lumi-nous colours of warmwhite (ww), neutralwhite (nw) and daylightwhite (dw).

Section of the chroma-ticity diagram with the curve relating to thePlanckian radiator andthe colour loci of stan-dard illuminants A (in-candescent light) and D 65 (daylight) plus thecolour loci of typicallight sources: candle-light (1), incandescentlamp (2), halogen lamp(3), fluorescent lamps inww (4),nw (5)and dw (6).

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150

50

400 600 800

Se

¬ (nm)

250

150

50

400 600 800¬ (nm)

Se

2.5 Light2.5.4 Luminous colour and colour

rendering

thermal radiator. It is possible to differen-tiate between three main groups of luminous colours here: the warm whiterange which resemble most closely colourtemperatures below 3300 K, the neutralwhite range between 3300 and 5000 K and the daylight white range which resemble most closely colour temperaturesabove 5000 K.

The colour of illuminated objects is the re-sult of the spectral composition of the light falling on a body and the ability ofthe body to absorb or transmit certaincomponents of this light and only reflector absorb the remaining frequency ranges.

In addition to the resulting, objectivecalculable or measurable colour stimulusthe colour adaptation of the eye alsoplays a role in our actual perception ofthings around us. The eye is able to gradually adapt to the predominant lumi-nous colour – similar to the way it adaptsto a luminance level – which means that in the case of a lighting situation thatcomprises different luminous colours virtually constant perception of the scaleof object colours is guaranteed.

The degree of deviation is referred to asthe colour rendering of the light source.Colour rendering is defined as the degreeof change which occurs in the colour effect of objects through lighting with a specific light source in contrast to thelighting with a comparative reference light source. It is therefore a comparisonof the similarity of colour effects undertwo types of lighting.

Since the eye can adapt to differentcolour temperatures, colour renderingmust be determined in relation to lumi-nous colour. One single light source cannot therefore serve as the source of reference; the standard of comparisonis rather a comparable light source with a continuous spectrum, be it a thermalradiator of comparable colour temperature,or daylight.

To determine the colour rendering ofa light source the colour effects of a scaleof eight object colours are calculated under the types of lighting to be evaluatedas well as under comparison standardlighting, and the two then compared. The quality of the colour rendering esta-blished is expressed as a colour renderingindex, which can be related to both general colour rendering (Ra) as well asthe rendering of individual colours. The maximum index of 100 represents optimum colour rendering, and lower values correspondingly less adequate colourrendering.

The quality of colour rendering is dividedinto four categories, in Germany accordingto DIN standards. These stipulate the minimum requirements for colour renderingfor lighting in workplaces. Colour rende-ring categories 1 and 2 are further sub-

divided– into A andB–to allow a differen-tiated evaluation of light sources.

Colour rendering category 1 is requiredfor tasks which involve the evaluation ofcolours. For the lighting of interior spaces,offices and industrial workplaces with de-manding visual tasks the minimum colourrendering category required is 2, wherebycolour rendering category 3 is sufficientfor industrial workplaces. Colour renderingcategory 4 is only permitted when the lowest of requirements are to be met atilluminance levels of up to 200 lux.

The colour rendering quality is an impor-tant criteria when choosing a light source.The degree of colour fidelity, therefore, by which illuminated objects are renderedin comparison to reference lighting. Insome cases the index for the rendering ofa specific colour has to be taken into account, e.g. in the field of medicine orcosmetics, when skin colours have to bedifferentíated.

Apart from the rendition quality thechoice of luminous colour is also of criticalimportance for the actual effect of colours.Blue and green colours will appear greyand dull under incandescent light despiteits excellent colour rendering properties.The same colours will be seen as clear andbright under daylight white fluorescentlight – although its colour rendering pro-perties are not so good. The same appliesthe other way round for the rendition ofyellow and red colours.

The lighting designer’s decision as towhich light source to select therefore depends on the given situation. Some in-vestigations indicate that a warm colourappearance is preferred at low illuminancelevels and in the case of directed light,whereas cold colour appearances are accepted for high illuminance levels anddiffuse lighting.

In the case of display lighting the coloursof the illuminated objects can be madeto appear brighter and more vivid throughthe purposeful application of luminouscolour – if necessary, using average colourrendering. This way of purposefully emphasizing colour qualities can also beapplied in retail lighting.

The lighting under which a customerdecides which articles he wishes to purchaseshould not deviate significantly from the lighting conditions the customer isaccustomed to.

84

Spectral distribution Se (l) of standard illumi-nants A (incandescentlight, above) and D 65(daylight, below).

Correlated colour temperature T of typical light sources.

Colour rendering categories and theirinherent Ra indices.

Light source T (K)

Candle 1900–1950Carbon filament lamp 2100Incandescent lamp 2 700–2 900Fluorescent lamps 2 800–7 500Moonlight 4100Sunlight 5 000–6 000Daylight 5 800–6 500(sunshine, blue sky)Overcast sky 6 400–6 900Clear blue sky 10 000–26 000

Colour renderingCategory Ra index1 A Ra > 901 B 80 ≤ Ra ≤ 902 A 70 ≤ Ra < 802 B 60 ≤ Ra < 703 40 ≤ Ra < 604 20 ≤ Ra < 40

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2.6 Controlling light2.6.1 Principles

Luminaires have a number of functions.The first is to accommodate one or morelamps plus any necessary control gear.Mounting, electrical connection and servicing must be as easy and safe as possible.

The construction of the luminairesguarantees that the user is protected fromcontact with live components (electricshock) and that there is no danger of surrounding surfaces and objects over-heating (fire prevention). Luminaires thatare to be applied under specific operatingconditions – e.g. rooms where there is adanger of an explosion, or damp or humidspaces – must be designed to meet themore stringent requirements. Besides theseelectrical and safety aspects luminairesalso have an aesthetic function as an integral part of the architectural designof a building. It is equally important that the form and arrangement ofthe luminaires and the lighting effects are appropriate.

The third and perhaps most essentialtask the luminaire has to fulfil is to control the luminous flux. The aim is toproduce a light distribution in accordancewith the specific functions the luminaireis required to fulfil, utilizing energy as effectively as possible.

Even in the days of the first artificial lightsource, the flame, luminaires were develo-ped to ensure that the light source couldbe mounted and transported safely. Withthe advent of considerably stronger lightsources – first gas lighting and later electric lamps – it became more importantto construct luminaires that could controlluminance and ensure that the light wasdistributed as required.

Luminaire technology was first con-fined to providing a shielding element forthe lamp and reducing the luminous in-tensity of the lamp by means of diffusinglampshades or canopies. This was one wayof limiting glare, but did not control the distribution of the light, which was absorbed or able to scatter in un-defined directions. You will still find thiscombination of lamp and lampshade today – especially in the decorative market – in spite of their being relativelyinefficient.

The introduction of reflector and PARlamps, which were used widely in the USA,marked the first step towards controllinglight purposefully and efficiently. In theselight sources the light is concentrated by the reflectors that form an integral partof the lamp and efficiently directed as required in defined beam angles. In contrast to luminaires with exposed lamps,the lighting effect was therefore no longer confined to the vicinity of the luminaire. It became possible to accentu-ate specific areas from almost any pointwithin the space. The reflector lamp took on the task of controlling the light;

the luminaire only served as a device tohold the lamp and as a means for limitingglare.

One disadvantage of reflector lampswas the fact that every time you replacedthe lamp you also replaced the reflector,which meant high operating costs. Apartfrom that, there were only a few standar-dised reflector types available, each with different beam angles, so for specialtasks – e.g. asymmetrical light distributionin the case of a washlight – there was fre-quently no suitable reflector lamp availa-ble. The demand for more differentiatedlighting control, for enhanced luminaireefficiency and improved glare limitationled to the reflector being taken from thelamp and integrated into the luminaire.This means that it is possible to constructluminaires that are designed to meet thespecific requirements of the light sourceand the task which can now be applied asinstruments for differentiated lighting effects.

2.6.1 Principles of controlling light

Various optical phenomena can be used inthe construction of luminaires as a meansfor controlling light:

2.6.1.1 Reflection

In the case of reflection, the light fallingonto a surface is fully or partially reflected,depending on the reflecting coefficient of this surface. Besides reflectance thedegree of diffusion of the reflected lightis also significant. In the case of specularsurfaces there is no diffusion. The greaterthe diffusing power of the reflecting surface, the smaller the specular componentof the reflected light, up to the point whereonly diffuse light is produced.

Specular reflection is a key factor in the construction of luminaires; the pur-poseful control of light can be achievedthrough specially designed reflectors andsurfaces, which also define the light out-put ratio.

2.6.1.2 Transmission

Transmission describes how the light fal-ling on a body is totally or partially trans-mitted depending on the transmissionfactor of the given body. The degree of diffusion of the transmitted light mustalso be taken into account. In the case of completely transparent materials thereis no diffusion. The greater the diffusingpower, the smaller the direct componentof the transmitted light, up to the pointwhere only diffuse light is produced.

Transmitting materials in luminairescan be transparent. This applies to simplefront glass panels, or filters that absorbcertain spectral regions but transmit others,

85

Controlling light

2.6

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Metals

Aluminium, highly specular 0.80–0.85Aluminium, anodised, matt finish 0.75–0.85Aluminium, matt finish 0.50–0.75Silver, polished 0.90Copper, polished 0.60–0.70Chrome, polished 0.60–0.70Steel, polished 0.50–0.60

Building materials

Plaster, white 0.70–0.85Gypsum 0.70–0.80Enamel, white 0.60–0.70Mortar, light 0.40–0.50Concrete 0.30–0.50Granite 0.10–0.30Brick, red 0.10–0.20Glass, clear 0.05–0.10

Paint finish

White 0.70–0.80Pale yellow 0.60–0.70Pale green, light red, pale blue, light grey 0.40–0.50Beige, ochre, orange, mid-grey, 0.25–0.35dark grey, dark red, 0.10–0.20dark blue, dark green

I L

I L

2.6 Controlling light2.6.1 Principles

86

Luminous intensitydistribution I (top left)and luminance dis-tribution L (top right) inthe case of diffuse re-flection. The luminancedistribution is the samefrom all angles of view.Luminous intensitydistribution in the caseof mixed reflection(centre) and specularreflection (below).

Reflection factor ofcommon metals, paintcolours and buildingmaterials.

Specular reflection ofparallel beams of lightfalling onto a flat sur-face (parallel path ofrays), concave surface(converging rays) andconvex surface (diver-ging rays).

Luminous intensitydistribution I (top left)and luminance dis-tribution L (top right) inthe case of diffusetransmission. The lumi-nance distribution isthe same from allangles of view. Luminousintensity distributionin the case of mixedtransmittance (centre)and direct trans-mittance through trans-parent material (below).

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n1 n2

™2™1

n1n2

™G

2.6 Controlling light2.6.1 Principles

thereby producing coloured light or a re-duction in the UV or IR range. Occasionallydiffusing materials – e.g. opal glass oropal plastics – are used for front covers inorder to reduce lamp luminance and helpto control glare.

2.6.1.3 Absorption

Absorption describes how the light fallingon a surface is totally or partially absorbeddepending on the absorption factor of thegiven material.

In the construction of luminaires absorption is primarily used for shieldinglight sources; in this regard it is essential for visual comfort. In principle, absorptionis, however, not wanted, since it does not control, but rather wastes light, there-by reducing the light output ratio of the luminaire. Typical absorbing elementson a luminaire are black multigroovedbaffles, anti-dazzle cylinders, barn doorsor louvres in various shapes and sizes.

2.6.1.4 Refraction

When beams of light enter a clear trans-mitting medium of differing density – fromair into glass and vice versa from glassinto the air, for example – it is refracted,i.e. the direction of its path is changed. In the case of objects with parallel surfacesthere is only a parallel light shift, whereasprisms and lenses give rise to optical effects ranging from change of radiationangle to the concentration or diffusion of light to the creation of optical images.In the construction of luminaires re-fracting elements such as prisms or lensesare frequently used in combination withreflectors to control the light.

2.6.1.5 Interference

Interference is described as the intensifi-cation or attenuation of light when wavesare superimposed. From the lighting pointof view inteference effects are exploitedwhen light falls on extremely thin layersthat lead to specific frequency rangesbeing reflected and others being trans-mitted. By arranging the sequence of thinlayers of metal vapour according to defined thicknesses and densities, selectivereflectance can be produced for specificfrequency ranges. The result can bethat visible light is reflected and infraredradiation transmitted, for example – as isthe case with cool-beam lamps. Reflectorsand filters designed to produce colouredlight can be manufactured using thistechnique. Interference filters, so-calleddichroic filters, have a high transmissionfactor and produce particularly distinctseparation of reflected and transmittedspectral ranges.

87

When transmitted fromone medium with a refractive index of n1into a denser mediumwith a refractive indexof n2 rays of light arediffracted towards theaxis of incidence (™1> ™2).For the transition from air to glass the re-fractive index is approx.n2/ n1=1.5.

When transmittedthrough a medium of adifferent density, rays are displaced in parallel.

Typical ray tracing through an asymmetri-cal prismatic panel(top left), symmetricalribbed panel (top right),Fresnel lens (bottomleft) and collecting lens(bottom right).

There is an angular limit™G for the transmissionof a ray of light from a medium with a refractive index of n2into a medium of lessdensity with a refractiveindex of n1. If this critical angle is exceededthe ray of light is re-flected into the densermedium (total reflec-tion). For the transitionfrom glass to air theangular limit is approx.™G = 42°. Light guidesfunction according to the principle of totalinternal reflection (be-low).

= n2n1

sin ™1sin ™2

sin ™G = n2n1

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1

2

34

3

2

1

2

3 4

2.6 Controlling light2.6.2 Reflectors

2.6.2 Reflectors

Reflectors are probably the most importantelements in the construction of lumi-naires for controlling light. Both reflectorswith diffusely reflecting surfaces – mostlywhite or with a matt finish – and highlyspecular surfaces are used. These reflectorswere originally made of glass with a mirrored rear surface, which led to the termwhich is still used today: mirror reflectortechnology. Anodized aluminium orchrome or aluminium-coated plastic aregenerally used as reflector material today.Plastic reflectors are reasonably low-priced,but can only take a limited thermal loadand are therefore not so robust as aluminiumreflectors, whose highly resistant anodizedcoating provides mechanical protectionand can be subjected to high temperatures.

Aluminium reflectors are available in a variety of qualities, ranging from high-quality super-purity aluminium to reflec-tors with only a coating of pure aluminium.The thickness of the final anodised coating depends on the application; forinterior applications it is around 3–5 µm,for luminaires to be used in exterior spacesor chemically aggressive environments up to 10 µm. The anodising process can be applied to the aluminium coil (coil anodising) or on the finished reflectors(stationary anodising), which is more ex-pensive.

The surfaces of the reflectors can havea specular or matt finish. The matt finishproduces greater and more uniform reflector luminance. If the reflected lightbeam is to be slightly diffuse, be it to attainsofter light or to balance out irregularitiesin the light distribution, the reflector surfaces may have a facetted or hammeredfinish. Metal reflectors may receive adichroic coating, which can control lightluminous colour or the UV or IR component.

Light distribution is determined to a large extent by the form of the reflector.Almost all reflector shapes can be attributedto the parabola, the circle or the ellipse.

88

Circle (1), ellipse (2), parabola (3) and hyper-bola (4) as the sectio-nal planes of a cone(above). Diagram of the sectional planesand sections (below).

Ray tracing from apoint light sourcewhen reflecting oncircle, ellipse, para-bola and hyperbola(from top to bottom).

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å1

å

1

å

2.6 Controlling light2.6.2 Reflectors

2.6.2.1 Parabolic reflectors

The most widely used reflectors are para-bolic reflectors. They allow light to becontrolled in a variety of ways – narrow-beam, wide-beam or asymmetrical dis-tribution, and provide for specific glare limitation characteristics.

In the case of parabolic reflectors thelight emitted by a light source located atthe focal point of the parabola is radiatedparallel to the parabolic axis. The morethe light source deviates from the idealpoint source – in relation to the diameterof the parabola – the more the rays oflight emitted will diverge.

If the reflector contour is constructedby rotating a parabola or parabolic segmentaround its own axis, the result is a reflectorwith narrow-beam light distribution. In the case of linear light sources a similareffect is produced when rectangular re-flectors with a parabolic cross section areused.

If the reflector contour is constructedby rotating a parabolic segment aroundan axis, which is at an angle to the para-bolic axis, the result is a reflector withwide-beam to batwing light distributioncharacteristics. Beam angles and cut-offangles can therefore basically be defined as required, which allows luminaires to be constructed to meet a wide range of light distribution and glare limitationrequirements.

Parabolic reflectors can also be appliedwith linear or flat light sources – e.g. PARlamps or fluorescent lamps, althoughthese lamps are not located at the focalpoint of the parabola. In this case the aimis not so much to produce parallel direc-tional light but optimum glare limitation.In this type of construction the focalpoint of the parabola lies at the nadir ofthe opposite parabolic segments, with theresult that no light from the light sourcelocated above the reflector can be emit-ted above the given cut-off angle. Suchconstructions are not only possible in luminaires, but can also be applied todaylight control systems; parabolic louvres – e.g. in skylights – direct the sun-light so that glare cannot arise above thecut-off angle.

89

Parabolic reflector withshort distance betweenfocal point and apex of the reflector; reflectoracts as a cut-off element.

Parabolic reflector withgreater distance be-tween focal point andapex of the reflector; noshielding for direct rays.

Parabolic reflector withgreater distance be-tween focal point andapex of the reflector,spherical reflector as ashielding element.

Parabolic contours of rectangular reflectors androtationally symmetricalreflectors.

Parabolic reflector withintense directional light(above). Wide-angle parabolic reflector withcut-off angle å (below).

Reflector contours forparallel rays / parabola(top left), convergingrays /ellipse (top right),diverging rays /hyper-bola (bottom left) andconverging-divergingrays (bottom right).

Parabolic reflector forglare limitation for flatand linear light sour-ces. When the focalpoint is located at thenadir (1) of the oppositeparabolic segment nolight is radiated abovethe cut-off angle å.

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å

30˚ 40˚ 50˚

2.6 Controlling light2.6.2 Reflectors

2.6.2.2 Darklight reflectors

In the case of the above-mentioned para-bolic reflectors clearly defined light radia-tion – and effective glare limitation – isonly possible for exact, point light sources.When using larger radiating sources – e.g. frosted incandescent lamps – glarewill occur above the cut-off angle; glareis visible in the reflector, although thelamp itself is shielded. By using reflectorswith a variable parabolic focal point (so-called darklight reflectors) this effectcan be avoided; brightness will then onlyoccur in the reflector of larger radiatingsources below the cut-off angle, i.e. whenthe light source is visible.

2.6.2.3 Spherical reflectors

In the case of spherical reflectors the lightemitted by a lamp located at the focalpoint of the sphere is reflected to this focal point. Spherical reflectors are usedpredominantly as an aid in conjunctionwith parabolic reflectors or lens systems.They direct the luminous flux forwardsonto the parabolic reflector, so that it alsofunctions in controlling the light, or to utilize the light radiated backwards bymeans of retroreflection back towards thelamp.

2.6.2.4 Involute reflectors

Here the light that is emitted by the lampis not reflected back to the light source,as is the case with spherical reflectors, butreflected past the lamp. Involute reflec-tors are mainly used with discharge lampsto avoid the lamps over-heating due to the retro-reflected light, which would result in a decrease in performance.

2.6.2.5 Elliptical reflectors

In the case of elliptical reflectors the lightradiated by a lamp located at the first focal point of the ellipse is reflected to thesecond focal point. The second focal pointof the ellipse can be used as an imaginary,secondary light source.

Elliptical reflectors are used in recessedceiling washlights to produce a light effectfrom the ceiling downwards. Elliptical reflectors are also ideal when the smallestpossible ceiling opening is required fordownlights. The second focal point will bean imaginary light source positioned at ceiling level; it is, however, also possibleto control the light distribution and glare limitation by using an additional para-bolic reflector.

90

Darklight technology.By using reflectors with a variable para-bolic focal point no light is radiatedabove cut-off angle å, especially in the case of volume radiatingsources.

Through the calculationof specific reflectorcontours various cut-off angles and distri-bution characteristicscan be obtained for thesame ceiling openingand lamp geometry.

Involute reflectors:light radiated by thelamp is reflected pastthe light source.

Elliptical reflectors indouble-focus down-lights (above), wall-washers (centre) andspotlights (below).

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1 2

1 2

2.6 Controlling light2.6.3 Lens systems

2.6.3 Lens systems

In contrast to prismatic louvres, lenses areused practically exclusively for luminairesfor point light sources. As a rule the opticalsystem comprises a combination of onereflector with one or more lenses.

2.6.3.1 Collecting lenses

Collecting lenses direct the light emitted bya light source located in its focal point to a parallel beam of light. Collecting lensesare usually used in luminaire constructionstogether with a reflector. The reflector directs the overall luminous flux in beamdirection, the lens is there to concentratethe light. The distance be-tween thecollecting lens and the light source isusually variable, so that the beam anglescan be adjusted as required.

2.6.3.2 Fresnel lenses

Fresnel lenses consist of concentricallyaligned ring-shaped lens segments. The optical effect of these lenses is compara-ble to the effect produced by conventio-nal lenses of corresponding shape or curvature. Fresnel lenses are, however,considerably flatter, lighter and less ex-pensive, which is why they are frequentlyused in luminaire construction in place of converging lenses.

The optical performance of Fresnellenses is confined by aberration in the regions between the segments; as a rulethe rear side of the lenses is structured to mask visible irregularities in the light dis-tribution and to ensure that the beamcontours are soft. Luminaires equippedwith Fresnel lenses were originally mainlyused for stage lighting; in the meantimethey are also used in architecturallighting schemes to allow individual adjustment of beam angles when the distance between luminaires and objectsvaries.

2.6.3.3 Projecting systems

Projecting systems comprise an ellipticalreflector or a combination of spherical re-flector and condenser to direct light at a carrier, which can be fitted with opticalaccessories. The light is then projected on the surface to be illuminated by the mainlens in the luminaire.

Image size and beam angle can be defined at carrier plane. Simple apertureplates or iris diaphragms can produce variously sized light beams, and contourmasks can be used to create differentcontours on the light beam. With the aidof templates (gobos) it is possible to project logos or images.

In addition, different beam angles orimage dimensions can be selected depen-

91

Collecting lens (above)and Fresnel lens (below).The beam angle can bevaried by changing thedistance between lensand light source.

Projector with projec-ting system: a uniformlyilluminated carrier (1) isfocussed via a lens sy-stem (2). The ellipsoidalprojector (above) withhigh light output, andthe condenser projector(below) for high qualitydefinition.

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0˚ 30˚

60˚

90˚

-30˚

-60˚

-90˚

100

60

20

400 600 800¬(nm)

†(%) Red

100

60

20

400 600 800

†(%)

¬(nm)

Yellow

100

60

20

400 600 800

†(%)

¬(nm)

IR

100

60

20

400 600 800

†(%)

¬(nm)

UV

100

60

20

400 600 800

†(%)

¬(nm)

Blue

2.6 Controlling light2.6.4 Prismatic systems2.6.5 Accessories

ding on the focal length of the lenses. Incontrast to luminaires for Fresnel lenses it is possible to produce light beams withsharp contours; soft contours can be obtained by setting the projector out offocus.

2.6.4 Prismatic systems

Another optical means of controlling lightis deflection using prisms. It is knownthat the deflection of a ray of light whenit penetrates a prism is dependent on the angle of the prism. The deflection angleof the light can therefore be determinedby the shape of the prism.

If the light falls onto the side of theprism above a specific angle, it is not longerrefracted but reflected. This principle is also frequently applied in prismaticsystems to deflect light in angles beyondthe widest angle of refraction.

Prismatic systems are primarily usedin luminaires that take fluorescent lampsto control the beam angle and to ensureadequate glare limitation. This means that the prisms have to be calculated forthe respective angle of incidence andcombined to form a lengthwise orientedlouvre or shield which in turn forms theouter cover of the luminaire.

2.6.5 Accessories

Many luminaires can be equipped withaccessories to change or modify theirphotometric qualities. The most importantare supplementary filters, which providecoloured light, or reduce the UV or IRcomponent. Filters may be made of plasticfoil, although glass filters are more durable.Apart from conventional absorption filters there are also interference filters(dichroic filters) available, which havehigh transmission and produce exact separation of transmitted and reflectedspectral components.

Wider and softer light distributioncan be achieved using flood lenses, whereassculpture lenses produce an elliptical lightcone. Additional glare shields or honey-comb anti-dazzle screens can be used to improve glare limitation. In the case ofincreased risk of mechanical damage,above all in sports facilities and in areasprone to vandalism, additional protectiveshields can be fitted.

92

Light head of a spot-light to which variousaccessories can be fitted.

Accessories (from thetop down): flood lensesto widen the light beam.Sculpture lens to pro-duce an oval light beam.Multigroove baffle andhoneycomb anti-dazzlescreen to control thelight beam and reduceglare.

Typical light distributionof a fluorescent lampequipped with prismaticoptics.

Spectral transmission † (¬)for conventional filters.

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2.6 Controlling light

93

Heat sink made of castaluminium

Lamp housing

Terminal block

Tilting stirrup for adju-sting the lamp bracket

Fixed darklight reflector

PAR lamp as light sourceand integral part of theoptical system

Mounting ring

Recessed directionalspotlight for PAR lamp.Recessed directionalspotlights are both dis-creet and flexible,blending harmoniouslywith the ceiling designand with all the advantages of conven-tional spotlights

Ceramic lamp holderfor E 27 cap

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2.7 Luminaires2.7.1 Stationary luminaires

There are various types of luminairesavailable. One main group comprises decorative luminaires, where outward appearance is more important than thelight they produce. We will not be dealingwith this type of luminaire in depth. This book is more concerned with luminaireswith clearly defined photometric qualitiesthat can be applied in the field of archi-tectural lighting. This sector also comprisesa wide range of luminaire types, whichcan be classified accordng to different criteria. For our purposes we have dividedthese into three main groups: stationary luminaires, movable luminaires and lightstructures.

2.7.1 Stationary luminaires

Stationary luminaires are an integral partof the architecture. Occasionally it is possible to vary light direction, but rigidmounting usually means that the light direction is also fixed. Stationary luminairescan be further subdivided according to luminaire characteristics and design.

2.7.1.1 Downlights

As the name implies, downlights directlight predominantly downwards. Down-lights are usually mounted on the ceiling.They may be recessed, which means thatthey are hardly visible as luminaires andonly effective through the light they emit.Downlights are, however, also available as surface or pendant luminaires. A specialversion, which is found more in hallwaysor exterior spaces, is the wall-mounteddownlight.

In their basic form downlights thereforeradiate light vertically downwards. They are usually mounted on the ceiling and illuminate the floor or other horizontalsurfaces. On vertical surfaces – e.g. walls– the light patterns they produce have a typical hyperbolic shape (scallops).

Downlights are available with differentlight distributions. Narrow-beam down-lights only light a small area, but give riseto fewer glare problems due to their steepcut-off angle. Some downlight formshave supplementary louvre attachmentsin the reflector aperture as an extra protection against glare. In the case ofdownlights with darklight reflectors thecut-off angle of the lamp is identical to the cut-off angle of the luminaire, thereby producing a luminaire with optimalwide-angle light distribution and lightoutput ratio.

94

Luminaires

2.7

Recessed downlight forincandescent lamps.Darklight technology,where the cut-off angleof the lamp is identicalto the cut-off angle ofthe luminaire.

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30˚

40˚

50˚

2.7 Luminaires2.7.1 Stationary luminaires

Double-focus downlights have similarproperties to conventional downlights,but the special form of the reflector allowshigh luminous efficiency even though the ceiling aperture is small.

Washlights have asymmetrical lightingdistribution, which not only directs thelight vertically downwards, but also directlyonto vertical surfaces. They are used to achieve uniform illumination over wallsurfaces as a complement to horizontallighting. Depending on the type usedwashlights are designed to illuminate asection of a wall, the corner of a space ortwo opposite sections of wall.

95

Mounting options fordownlights: recessed,semi-recessed, surface,pendant and wall mounting.

Recessed downlight forhigh-pressure dischargelamps. Lamp and re-flector are separatedby a safety glass cover.

Recessed downlightsfor compact fluores-cent lamps, versionswith integrated and separate control gear(above) and with cross-blade louvre (below).

Installation of double-focus downlights inhorizontal and inclinedceilings.

Symbolic representation in plan view: washlights,double washlights and corner washlights.

Washlights with dark-light reflectors and additional ellipsoidalsegment for the walllighting.

Double-focus down-light with ellipsoidalreflector and additionalparabolic reflector withespecially small ceilingaperture.

Different reflector shapes produce different cut-offangles from the same ceiling aperture.

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L (dB(A))

40

20

100 140 180V (m3/h)

0.6

0.2

100 140 180V (m3/h)

1.0 Residual heat factor

40˚

360˚

2.7 Luminaires2.7.1 Stationary luminaires

Directional spotlights provide accentlighting of specific areas or objects. By redirecting the light beam they can be used for different lighting tasks. Their light distribution is narrow to medium.

Air-handling downlights are availableas air-return and air-handling luminaires.They represent a dual function solutioncomprising lighting and air-conditioningand make for harmonious ceiling design.Air-handling luminaires can be providedwith connections for fresh air supply, for air return or for both air-supply and air-return.

Downlights are available for a wide rangeof lamps. Those most frequently used are compact light sources such as incandes-cent lamps, halogen lamps, high-pressuredischarge lamps and compact fluorescentlamps.

96

Directional spotlightwith adjustable reflec-tor lamp and darklightreflector. Directionalspotlights can generallybe rotated 360°and inclined to 40°.This means that the di-rectional spotlight canbe directed at both horizontal and verticalsurfaces.

Directional spotlightwith darklight reflector.

Directional spotlightwith anti-dazzle mask.

Directional spotlightwith cardanic suspension.

Directional spotlight,spherical version.

Noise level range L in relation to volumeof return air flow V. Typical values for down-lights.

Residual heat factorin relation to volumeof return air flow V.Typical values for down-lights.

Downlight with com-bined air-supply andair-return.

Air-handling downlightdesigned for an incan-descent lamp. The con-vection heat producedby the lamp is removedwith the air flow.

Downlight with air-return function, de-signed for a compactfluorescent lamp. Thereturn air is dissipatedseparately, because the cooling effect ofthe return air may influence the perfor-mance of the lightsource.

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18

24

18 36, 40, 55

36

58

90 I (cm)6030 T [W] TC-L [W]

18

24

36, 40, 55

90 I (cm)6030 T [W] TC-L [W]

18

24

36

2.7 Luminaires2.7.1 Stationary luminaires

2.7.1.2 Uplights

In contrast to downlights, uplights emitlight upwards. They can therefore be usedfor lighting ceilings, for indirect lighting by light reflected from the ceiling or forilluminating walls using grazing light. Uplights can be mounted on or in the flooror wall.

Up-downlights combine a downlight andan uplight in one fixture. These luminairesare applied for the simultaneous lighting of floor and ceiling or for grazing lightingover a wall surface. They are available inwall and pendant versions. .

2.7.1.3 Louvred luminaires

Louvred luminaires are designed for linearlight sources such as fluorescent lampsor compact fluorescent lamps. Their namederives from their anti-dazzle attachmentsthat may be anti-glare louvres, light controlling specular reflectors or prismaticdiffusers.

Being fitted with linear light sourcesof low luminance louvred luminaires produce little or no modelling effects. Theygenerally have wide-beam light distribution,with the result that louvred luminairesare predominantly used for lighting wideareas.

Louvred luminaires are usually long andrectangular in shape (linear fluorescents);square and round versions are also availablefor compact fluorescent lamps. Similar to downlights, they are available for re-cessed or surface mounting or as pendantfixtures.

97

Sectional drawing of a recessed floor luminairefor halogen reflectorlamps.

Comparison of shapesand sizes of louvredluminaires for differentlamps.

Louvred luminaire forfluorescent lamps withdarklight reflector andinvolute upper reflector.Louvred luminaires canbe rectangular, squareor round.

Mounting options foruplights and combineduplight/downlight:wall mounting, floormounting, recessedfloor mounting.

Wall-mounted combineduplight and downlightfor PAR lamps.

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3.3 Luminaires3.32 Stationary luminaires

In their basic form louvred luminaires haveaxially symmetrical light distribution. Theyare available with cut-off angles of 30°to 40° and a variety of beam characteristics,so light distribution and glare limitationcan be selected to suit the respective re-quirements. If a reduction in reflectedglare is required, louvred luminaires withbatwing distribution can be used. They emit light at predominantly low angleswith the result that very little light is emitted in the critical reflecting range.Direct glare caused by louvred luminairescan be controlled in a number of ways.The simplest is the application of anti-dazzlelouvres to limit the distribution angle. Enhanced luminaire efficiency is bestachieved by light-controlling louvres. Theselouvres can have a highly specular or mattfinish. Louvres with a matt finish provideuniform surface luminance in line with theluminance of the ceiling. In the case ofhighly specular reflectors, the louvre withinthe cut-off angle can appear to be dark,but they do sometimes lead to unwantedreflections in the louvre. A further means for controlling light in louvred luminairesis by using prismatic diffusers.

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Different versions oflouvred luminaires(from the top down-wards): luminaire withtransverse louvres, lu-minaire with paraboliclouvres, luminaire withparabolic louvres andprismatic lamp diffuserfor improving contrastrendition, luminairewith prismatic louvre.

Lamp arrangement in lou-vred luminaires: standardarrangement above thetransverse louvres (topleft). Lamp position to increase the cut-off angle(centre left). Twin-lampversion with lamps arran-ged horizontally and verti-cally (below left and topright). Lateral position forasymmetrical light distri-bution (centre right). Twin-lamp version withtwin-louvre (below right).

Mounting options forlouvred luminaires: recessed ceiling, surface,mounting on tracks,walls, floor-standing orpendant mounting.

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30˚ 30˚

40˚ 40˚

-10˚ 10˚

-30˚ 30˚

-10˚ 10˚

-30˚ 30˚

-10˚ 10˚

-30˚ 30˚

-10˚ 10˚

-30˚ 30˚

2.7 Luminaires2.7.1 Stationary luminaires

Asymmetric louvred luminaires predo-minantly radiate light in one directiononly. They can be used for the uniformlighting of walls or to avoid glare caused by light projected onto windows or doors.

VDT louvred luminaires are designed foruse in spaces with computer workstations.In Germany they must have a cut-offangle of at least 30° along both main axesand must not exceed an average lumi-nance of 200 cd/m2 above the cut-off angle.They are therefore generally equippedwith highly specular louvres. When usingpositive contrast monitors higher lumi-nances are permissible, in critical cases acut-off angle of 40° may be required.

Direct-indirect louvred luminaires aresuspended from the ceiling or mounted on the wall. They produce a direct compo-nent on horizontal surfaces beneath the luminaire and at the same time lightthe ceiling and provide diffuse ambientlighting.

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Asymmetric louvred luminaires (from the topdown): the wall can be lit by tilting thesymmetrical reflector,lighting using a wall-washer with an ellipti-cal side reflector.Lighting without a wallcomponent (e.g. in thevicinity of a window)using a luminaire witha flat side reflector.

Cut-off angle of 30°(limiting angle 60°)along both main axes(above), cut-off angleof 40° (limiting angle50°) along both mainaxes (below).

Typical light distribu-tion curves for louvredluminaires: direct lu-minaire, direct-indirectluminaire with a predominantly directcomponent, direct-indirect luminaire witha predominantly indirect component,indirect luminaire.

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2.7 Luminaires2.7.1 Stationary luminaires

Air-handing louvred luminaires are de-signed to handle supply air and return airand provide a more harmonious ceilinglayout. Air-handling louvred luminaires canbe provided with connections/outlets forsupply air, return air, or both supply air andreturn air.

2.7.1.4 Washlights

Washlights are designed to provide uni-form lighting over extensive surfaces,mainly walls, ceilings and floors, there-fore. They are included in the group downlights and louvred luminaires, although washlights do have their ownluminaire forms.

Wallwashers illuminate walls and –depending on how they are designed –also a part of the floor. Stationary wallwashers are available as recessed and surface-mounted luminaires.

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Louvred luminaireswith air-return compo-nent for negative pressure ceilings, forfunnelling return air off into extract air ductsand for combined supply air and returnair handling.

Wallwashers for reflec-tor lamps with a lensto spread the lightbeam and a darklightreflector. Very littlelight is directed ontothe floor, the walllighting is especiallyuniform.

Wallwasher for compactfluorescent lamps.

Wallwasher with ellip-soidal reflector for halogen lamps.

Wallwasher with sculp-ture lens and reflectorattachment for reflectorlamps.

Wallwasher for fluore-scent lamps. The directlight component is cutoff, the reflector con-tour produces especiallyuniform lighting overthe wall surface. In thediagram below a sup-plementary prismaticdiffuser below ceilinglevel provides light directly from the top of the wall.

Cantilever-mounted wallwasher.

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2.7 Luminaires2.7.1 Stationary luminaires

Ceiling washlights are designed forbrightening or lighting ceilingsand for indirect ambient lighting. Theyare installed above eye height onthe wall or suspended from the ceiling. Ceiling washlights are generally equippedwith tungsten halogen lamps for mains voltage or with high-pressure dischargelamps.

Floor washlights are mainly used forlighting hallways and other circulationzones. Floor washlights are mounted in or on the wall at relatively low levels.

2.7.1.5 Integral luminaires

Some forms of lighting use the architec-tural elements as controlling components of the lighting. Typical examples are lumi-nous ceilings, cove lighting or concealedcornice lighting. Standard luminaires, e.g.for fluorescent lamps or high-voltage tubular lamps can be used for such applica-tions.

As a rule, lighting that is integratedinto the architecture is inefficient and,from a lighting engineering point of view,difficult to control. For this reason it doesnot play a significant role in the effectivelighting of spaces. Luminaires can be integrated into the architecture in order to accentuate architectural elements, e.g. to reveal contours. For this purpose theyare excellent.

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Different versions ofceiling washlights:wall-mounted, free-standing luminaire orpairs of luminaires mounted on a standand suspended version.

Different versions offloor washlights: roundand square versions forincandescent lamps or compact fluorescentlamps, rectangular version for fluorescentlamps. Luminaires integrated

into the architecture,e.g. suspended ceilingelements, coffered cei-lings and vaulted ceilings and in wallconstructions.

Wall-mounted floorwashlight. The directlight component is re-stricted, the reflectorshape produces uni-form lighting of thefloor.

Wall-mounted ceilingwashlight. The reflectorcontours produce uni-form ceiling lighting.

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2.7 Luminaires2.7.2 Movable luminaires

2.7.2 Movable luminaires

In contrast to stationary luminaires movableluminaires can be used in a variety of locations; they are generally used in tracksystems or in light structures. Movable luminaires usually also allow changes in light direction, they are not confined to a fixed position, but can be adjusted andrepositioned as required.

2.7.2.1 Spotlights

Spotlights are the most common form ofmovable luminaires. They illuminate a limited area, with the result that they arerarely used for ambient lighting but pre-dominantly for accent lighting. In view oftheir flexibility with regard to mountingposition and light direction, they can be adjusted to meet changing requirements.

Spotlights are available in a variety of beam angles. Their narrow-beam lightdistribution provides for the lighting of small areas from considerable distances,whereas the wider light distribution inherent in wide-beam spotlights meansthat a larger area can be illuminated usinga single spotlight.

Spotlights are available for a wide rangeof light sources. Since the aim is generallyto produce a clearly defined, narrowbeam, designers tend to opt for compactlight sources such as incandescent lamps,halogen lamps and high-pressure dischargelamps, occasionally also compact fluores-cent lamps. Wide-beam spotlightsare mainly designed for larger lamps, suchas double-ended halogen lamps andhigh-pressure discharge lamps or compactfluorescent lamps, whereas point sources,such as low-voltage halogen lamps ormetal halide lamps provide an especiallyconcentrated beam of light.

Spotlights can be equipped with re-flectors or reflector lamps. Some modelscan be equipped with converging lenses orFresnel lenses to vary the beam angle.Spotlights with projecting systems allowa variety of different beam contours by the use of projection of masks or tem-plates (gobos).

Another characteristic of spotlights isthat they can be equipped with a widerange of accessories or attachments, suchas flood or sculpture lenses, colour filters,UV or infrared filters and a range of anti-dazzle attachments, such as barn doors,anti-dazzle cylinders, multigroove bafflesor honeycomb anti-dazzle screens.

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An especially wide beamangle of approx. 90°is characteristic forfloodlights designedfor the lighting of wallsurfaces.

Spotlights for low-voltage halogen lampscan be operated onlow-voltage tracks; thetransformer can bemounted on the ceilingor be in an exposedposition on the track(above). When opera-ting on mains voltagetracks the transformeris usually integratedinto the adapter ormounted on the lumi-naire (below).

In the case of spotlightsdesigned for accentlighting the beam anglecan be varied by selecting from a rangeof reflectors or reflec-tor lamps. A distinctionis made between narrow beam angles of approx. 10° (spot)and wide-beam anglesof approx. 30° (flood).

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2.7 Luminaires2.7.2 Movable luminaires

2.7.2.2 Wallwashers

Wallwashers are not only available asstationary luminaires, but also as movableluminaires. In this case it is not so muchthe light direction that is variable, but theluminaire itself. On track, for example,movablewallwashers can provide temporaryor permanent lighting on vertical surfaces.Movable wallwashers are generally equipped with halogen lamps for mainsvoltage, metal halide lamps or with fluorescent lamps (linearand compact types).

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Accessories for spot-lights and projectors:honeycomb anti-dazzlescreen, sculpture lens,filter, anti-dazzle cylin-der, barn doors.

Different versions ofstage-type projectors(from the top down-wards): condenser pro-jector and ellipsoidalprojector with opticalsystems for projectingimages, parabolic pro-jector, projector for reflector lamps andFresnel projector withvariable beam angle.

Wallwashers for halogenlamps, compact fluore-scent lamps and linearfluorescent lamps.

Cantilevers with inte-gral transformer forlow-voltage spotlights;wall-mounted (above)and mounted on a par-tition wall (centre).Cantilevers for the mounting of lightstructures and indivi-dual luminaires (below).

Different versions ofmovable wallwashers.They can be adjustedto different wallheights and distances.

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2.7 Luminaires2.7.3 Light structures

2.7.3 Light structures

Light structures are systems comprisingmodular elements that take integrated luminaires. Movable luminaires, e.g. spot-lights, can be mounted and operated on light structures. They therefore allow a combination of stationary and movableluminaires.

Light structures can be formed of track,lattice beams, tubular profiles or panels.Their main feature is that they are modularsystems, comprising standardised basicelements and a selection of connectorsthat allow the construction of a wide variety of structures – from linear arran-gements to extensive grids. Light structurescan therefore be incorporated into the surrounding architecture or themselvescreate architectural structures; they aredesigned to be highly functional lightinginstallations blending in harmoniously withtheir surroundings.

One sub-group of light structures are carrier systems with integral power supply. They are designed exclusively forthe mounting and operation of movable luminaires. They can be track or tubular or panel systems with integral track.

Carrier systems can be mounted directly onto walls and ceilings, or suspen-ded from the ceiling. Carrier systems with a high load-bearing capacity are alsoavailable as large-span structures.

In the strict sense of the word lightstructures are characterised by the factthat they contain integral luminaires;if they also contain track or a series ofconnection points, they are also able to take movable luminaires, as required. Theyconsist of tubular or panel elements and are usually suspended from the ceiling.

Light structures frequently consist ofelements with integral louvred luminaires,which can be used for direct lighting andfor indirect lighting by light reflected offthe ceiling. For accent lighting elementswith integral downlights or directional luminaires (frequently equipped with low-voltage lamps) can be used; decorative effects can be produced by elements withexposed incandescent or halogen lamps.Other elements can take information signs.

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Carrier system withdownlight (top left),louvred luminaire (topright), ceiling wash-lights (bottom left) anduplight (bottom right).

Three-circuit track for mains voltage and single-phase low-voltage track.

Adapter with phase se-lection switch for three-circuit track.

Different types of lightstructures: from track to large-span structures.

End cap, connector,flexible connector,L-connector, T-connectorand X-connector fortrack.

Light structure; emptyprofile with variety ofattachments: louvredluminiares, downlights(also loudspeakers,connection points, etc.,if required), wall-washers, track, direc-tional spotlights andinformation signs.

Cross sections of lightstructures showing a variety of profile designs.

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2.7 Luminaires2.7.4 Secondary reflector luminaires2.7.5 Fibre optic systems

2.7.4 Secondary reflector luminaires

The widespread use of personal computerworkstations in modern-day office spaceshas led to a greater demand for improvedvisual comfort, above all with regard to limiting direct glare and discomfort glare.Glare limitation can be provided throughthe use of VDT-approved luminaires, orthrough the application of indirect lightinginstallations.

Exclusively indirect lighting that pro-vides illumination of the ceiling will avoidcreating glare, but is otherwise ineffectiveand difficult to control; it can producecompletely uniform, diffuse lightingthroughout the space. To create differen-tiated lighting and provide a component of directed light, it is possible to combinedirect and indirect lighting components in a two-component lighting system. Thismay consist of combining task lightingwith ceiling washlighting, or the use ofdirect-indirect trunking systems.

The use of secondary reflectors, whichis a relatively new development, makes for more comprehensive optical control.This means that the ceiling, which repre-sents an area of uncontrolled reflectance,is replaced by a secondary reflector whichis integrated into the luminaire andwhose reflection properties and luminancecan be predetermined. The combinationof a primary and a secondary reflectorsystem produces a particularly versatileluminaire, which is able to emit exclusivelyindirect light as well as direct and indirectlight in a variety of ratios. This guaranteesa high degree of visual comfort, evenwhen extremely bright light sources suchas halogen lamps or metal halide lamps are used, and while still being possible toproduce differentiated lighting.

2.7.5 Fibre optic systems

Light guides, or optical fibres, allow lightto be transported at various lengths andaround bends and curves. The actual lightsource may be located at a considerable distance from the light head. Optical fibresmade of glass are now so well developedthat adequate amounts of luminous fluxcan now be transmitted along the fibres forlighting applications.

Fibre optics are used above all in loca-tions where conventional lamps cannot be installed due to size, for safety reasonsor because maintenance costs would be ex-orbitant. The especially small-dimensionedfibre ends lend themselves perfectly to the application of miniaturised down-lights or for decorative starry sky effects.In the case of showcase lighting, glassdisplay cases can be illuminated from theplinth. Thermal load and the danger ofdamaging the exhibits are also considera-bly reduced due to the fact that the lightsource is installed outside the showcase.

In the case of architectural models several light heads can be taken from onestrong central light source, allowing lumi-naires to be applied to scale.

105

Secondary reflector luminaire; rectangularand square versions.

Direct-indirect and indirect secondary reflector luminaire.

Secondary reflector lu-minaire with a parabolicreflector for the directcomponent and involutesecondary reflectorfor the control of theindirect component.

Pendant direct-indirectsecondary reflector lu-minaire.

Typical light guide fix-tures (from the top downwards): down-light with reflector,downlight with lensoptics, directional spot-light with reflector,directional spotlightwith lens optics.

Fibre optic systemcomprising projector,flexible light guidesand individual lightheads for the ends ofthe fibres. Inside theprojector the lightemitted by a low-voltage halogen lamp is focussed onto theCommon End of thebundle of fibres by means of an ellipticalreflector. The light isthen conveyed alongthe individual light guides, and emitted atthe ends of the fibresthrough the attachedlight heads.

Rotationally symmetri-cal secondary reflec-tor luminaire for point sources (e.g. high-pressure dischargelamps). Illustrated versions with parabolicreflector or lens systemfor the direct component,and a luminaire with asecondary reflector only.

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2.7 Luminaires

106

Spotlights and wash-lights whose design isbased on fundamentalgeometrical forms.

Spotlights of differentdesigns and technicalperformance.

The development oflow-voltage halogenlamps allows the de-sign of luminaires of especially compact dimensions, in parti-cular for spotlights forlow-voltage track.

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2.7 Luminaires

107

Within a uniform de-sign concept the con-struction of luminairesfor a variety of lightsources and lightingtasks leads to a widerange of designs.

Stage projectors can be used for creating dramatic lighting effects, such as coloureffects and projectionsin large spaces.

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Lighting design3.0

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The scientific application of artificiallighting is a relatively young discipline. In contrast to daylighting, which looksback on a tradition that developed gra-dually over several thousand years, theneed to develop concepts for artificiallighting only became a requirement in thelast century or two. Just 200 years agoplanning using artificial light sources wasconfined to deciding where best to posi-tion the few candles or oil lamps available.Not really what might be referred to asadequate lighting design. Only in the lastone hundred years, with the rapid de-velopment of efficient light sources, haslighting design acquired the tools thatallow artificial lighting to be produced withadequate illuminance levels. This de-velopment is accompanied, however, bythe task of defining the objectives andmethods behind this new discipline, ofdeciding on the criteria by which the arti-ficial light that is now available is to beapplied.

3.1.1 Quantitative lighting design

The first and to date most effective con-cept has given rise to a set of standards orcriteria for the lighting of workplaces.While decisions with regard to lighting inthe private sector can be limited to thechoice of suitably attractive luminaires,there is a clear interest in the field of thelighting of workplaces to develop effec-tive and efficient forms of lighting. Themain concern is which illuminance levelsand types of lighting will ensure optimumvisual performance, high productivity and safety at operating costs which are affordable.

Both aspects of this task were exami-ned in detail, i.e. both the physiologicalquestion of the correlation of visual per-formance and lighting, and the technicalquestion of establishing criteria by whichthe quality of a lighting installation can be measured. The concept of quantitativelighting design with illuminance as thecentral criterion, followed by uniformity,luminous colour, shadow quality and thedegree of glare limitation, developed at arelatively early stage. Taking such criteriaas a basis, standards were compiled con-taining minimum illuminance levels onthe relevant working area for a wide varietyof activities, plus the minimum require-ments for the other quality criteria.

In practice, this would appear to re-quire uniform,mostly horizontally orientedlighting over the entire space, whichcould best be effected by a regular arran-gement of luminaires, e.g. continuous rowsof fluorescent linear luminaires or louvreddownlights. The illuminance level in eachcase is designed – in accordance with thedemand for uniform lighting – to meetthe requirements of the most complicatedvisual tasks that can be expected in thegiven space. The inevitable result is that

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3.1 Lighting design concepts3.1.1 Quantitative lighting design

Lighting designconcepts

3.1

Guide values for illumi-nance E for variousareas of activity inaccordance with CIErecommendations.

Type of lighting Area of activity Guideline E (lx)

Circulation routes 50General lighting Staircases and short-stay 100in short-stay spaces spaces

Rooms not continually in use – 200lobbies, public circulation

General lighting Office with daylight- 300in working spaces oriented workplace

Meeting and conference 300roomsOffice space, data processing 500Open-plan office, technical 750drawings and design officeComplicated visual tasks, 1000precision assembly,colour testing

Additional lighting 2000for very complicatedvisual tasks

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h

d

Viewpoint

3.1 Lighting design concepts3.1.1 Quantitative lighting design

the overall lighting is far too bright for all the other activities which will occur inthe area.

There is no doubt that quantitativelighting design concepts of this kind aresuccessful within the framework of thetask that has been set, as explained above.There is a proven correlation between the quality of the light and visual perfor-mance; this corresponds to the definableeffect which the quality of the lighting hason efficiency and safety at the workplace.

It is therefore justified to maintainthat the standard lighting conditions re-commended for a technical office mustbe different from those for a warehouse.But when consideration is given to thelighting required for working areas withdifferent or changing activities the limitsof quantitative lighting design conceptssoon become apparent. If the task is tolight a drawing board and a CAD worksta-tion, for example – nowadays a frequentconstellation – it soon becomes clear thatthe high illuminance level required for thedrawing board is disturbing to the personworking at the computer, indeed that thevertical light component required forwork at the drawing board may make itimpossible to work at the computer.

More light is therefore not alwaysnecessarily better light. Similarly, it is im-possible to put other lighting qualitiesinto any kind of basic order of importance– the measures taken to limit direct glaremay not work at all to limit reflectedglare; the light required to be able to readsmall print might be unbearable for rea-ding texts printed on glossy paper. Thefrequently encountered idea that an over-all illuminance level of 2000 lux withoptimum glare limitation and colour ren-dering will be the end of complaints fromoffice staff, is based on what can only be described as inadmissible simplification.Optimum lighting of different workplacescannot be effected by raising the overall“quantity” or brightness of the light, butonly by orienting the planning towardsthe requirements of the individual areas,in other words, by relaxing the require-ment for lighting to be uniform.

As can be readily appreciated, the limits ofquantitative lighting design soon becomeapparent in the actual field of applicationit was intended for, the lighting of work-places. Questionable though it is, this kindof lighting philosophy is widespread andis generally adopted as the standard forarchitectural lighting. On closer investiga-tion it is apparent that quantitativelighting design is based on an extremelysimplified perception model. Our entireenvironment is reduced to the term “visualtask”; all architectural considerations,the information content and aestheticquality of the visual environment aredisregarded. The same applies to the defi-nition of the perceiving person, who is

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Min. height h of emer-gency exit signs inescape routes in accor-dance with maximumviewing distance d(acc. to DIN 4844).

Safety lighting

Safety lighting allowspeople to leave roomsand buildings (safetylighting for escaperoutes), or to completeactivities and leaverooms with workplacesthat are exposed tohazards.

Regulations laid downin ASR 7/4 DIN 5035,Part 5, DIN 57108, VDE0108.

Requirements to bemet by safety lightingin workplaces exposedto hazards: minimumilluminance Emin,changeover time Δtand operating time t.

Standby lighting

Standby lighting(usually 10 % of the ra-ted illuminance) takesover from the artificiallighting to maintaincontinued operation fora defined period oftime, used to limit da-mage and loss of pro-duction, in particular.

Regulations laid downin DIN 5035, Part 5.

Requirements to bemet by safety lightingfor escape routes:minimum illuminanceEmin, uniformity Emin/Emax, change-over timeΔt and operating time t.

Emergency exit sign,backlit

dh =200

Illuminated emergencyexit sign

dh =100

Emergency lighting

Safety lighting

For workplaces subject to particular hazards

For escape routes

Standby lighting

Safety lightingWorkplaces exposed Escape routesto hazardsEmin = 0.1 En Emin ≥ 1 lxat least 15 lx (0.2 m above floor level)En acc. to DIN 5035, Part 2

E min 1≥Emax 40

Δt ≤ 0.5 s Δt ≤ 15 s (workplaces)Δt ≤ 1s ( meeting places,

business premises)

Δt ≥ 1 min, t = 1h (workplaces)at least for the period people t = 3h (meeting places,are subjected to danger business premises)

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102 103L (cd/m2)

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2

1

100 1012 5

3

4

2 5 2 5 2 5 2

3.1 Lighting design concepts3.1.2 Luminance technology

of simply changing reference criteria, butmore of expanding the design analysis tothe entire space. Whereas up to now anoverall illuminance level was planned forthe whole space based on the visualrequirements for the most complicatedvisual task, the approach now is to planluminance levels for all areas of a visualenvironment.

This means that it is now possibleto differentiate between the various visualtasks performed in a space, to defineroom zones where the lighting is adjustedto the specific activities carried out inthese areas. At this stage it is possible torefer to the standards and recommenda-tions laid down for quantitative lightingdesign when planning the lighting for theindividual visual tasks.

Design concepts based on luminancelevels are, however, not confined to ascer-taining spatial zones, which in turn wouldonly lead to splitting a space up into a se-ries of conventionally lit areas. The mainfeature of this kind of planning is that it isnot directed towards the lighting for visualtasks, but towards the brightness ratiobetween the visual tasks and their respec-tive surroundings, the balance of all lumi-nances within one zone. This presumesthat the lighting for one zone only allowsoptimum “stable” perception when theluminance contrasts do not exceed, or fallbelow, certain values. The aim is to createa constellation within which the visualtask forms the brightest area in the envi-ronment, thereby holding the attentionof the viewer. The luminance level of thesurroundings should therefore be lower so as not to distract the person’s view, butremain within a defined range of con-trast. The permissible scale of contrasts isa result of the state of adaptation of theeye while perceiving the visual task – in a“stable” environment the eye retains aconstant state of adaptation, whereas an“instable” environment leads to conti-nuous, tiring adaptation through too lowor too high background luminances.

When planning a “stable” spatialsituation with controlled luminance dis-tribution it is no longer possible to baseconcepts on a standardised lighting in-stallation. Just as luminance is a result ofthe correlation of the illuminance andreflectance of the surfaces, the lightinginstallation and the material qualitiesmust be planned together when designingconcepts based on luminance levels. Therequired luminance contrasts cannot onlybe achieved by varying the lighting, butalso by determining surrounding colours.The most prominent example is thelighting for the Museum of Art in Berne,where the especially intense and brightappearance of the paintings on display isnot achieved by increased illuminancelevels, but through the grey colour of thewalls. In this situation the paintings have a higher luminance than the relativelydark surrounding area, which makes their

effectively considered to be a walkingcamera – the only aspect that is taken intoaccount is the physiology of our vision;the psychology of perception is disregardedaltogether.

Design concepts based on these prin-ciples, which only serve to ensure safetyand a sound working economy, and ignoreany other requirements the perceivingperson may have of his visual environment,can lead to problems at the workplace.Outside the working environment the userwould inevitably find such lighting in-adequate; the lighting solution will remainclearly inferior to the feasible possibilities.

3.1.2 Luminance-based design

A quantitative lighting design conceptthat is oriented primarily towards provi-ding a recommended illuminance level,lacks the criteria to develop a concept thatgoes beyond the requirements thatwould ensure productivity and safety tomeet the needs of the architecture andthe persons using the architectural space.

In response to this problem a newkind of lighting philosophy is developed,as represented in Waldram’s “designedappearance” and Bartenbach’s “stable per-ception” models, for example. The aim ofthis approach is a process that not onlyprovides adequate lighting for visual tasksbut is also able to describe and plan theoptical effect of an entire space.

To be able to plan the visual effect of anenvironment the central reference quan-tity has to be changed. Instead of illumi-nance,which describes only the technicalperformance of a lighting installation, it isluminance that becomes the basic criteria– a dimension that arises from the correla-tion of light and lit environment, therebyforming the basis for human perception.Changing the central quantity to lumi-nance means that brightness and contrastratios can be established for the entireperceived space, be it between visual taskand background, between individualobjects or between objects and their sur-roundings.

This change of criteria does not makemuch difference to the lighting of visualtasks at the workplace, since the effect ofdifferent contrast ratios on visual perfor-mance are known and have been taken intoconsideration according to the degree ofdifficulty defined for the specific visualtasks. This does not apply for the lightingeffect in the entire space. Consideringluminance levels in this way means thatbrightness ratios produced by a lightinginstallation in correlation with the archi-tecture and the illuminated objects canbe ascertained and lighting concepts de-veloped based on the distribution ofbrightness.Designing concepts based on luminancelevels is therefore not so much a question

112

Ranges of typical lumi-nances L in interiorspaces: luminances outside working spaces(1), luminances ofroom surfaces (2),luminances of visualtasks at the workplace(3), tolerance luminan-ces of luminaires (4).

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ED

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LD

LWLS

LALI

3.1 Lighting design concepts3.1.2 Luminance technology

colours appear particularly intense –similar to projected slides or lighting usingframing projectors.

At first glance this appears to be a promi-sing concept, which avoids the weakpoints of quantitative lighting design andprovides criteria for a perception-orienteddesign theory. Considerable doubts havearisen from the perceptual psychologysector, however, as to whether luminanceand luminance distribution are suitablecriteria for a lighting design theory basedon human perception.

Luminance is indeed superior to illu-minance in as far as it forms the basis forperception – light itself is invisible. It canonly be perceived when it is reflected byobjects and surfaces. Luminance, however,is not identical to the brightness weactually perceive; the luminance pattern onthe retina only provides the basis forour perception, which is completed throughcomplex processes in the brain. This alsoapplies to luminance scales that are adju-sted to the state of adaptation of the eye or the conversion into equidistantgrades of brightness – there is no directcorrelation between the image actuallyperceived and the luminance pattern onthe retina.

If luminance were the only factor that determined our perception, we wouldbe helplessly exposed to an array of con-fusing patterns of brightness produced bythe world around us. We would never be in a position to distinguish the colour andreflectance of an object from differentlighting levels, or perceive three-dimen-sional forms. It is nevertheless exactlythese factors of constancy, the forms andmaterial qualities around us, that ourperception is aimed at; changing lumi-nance patterns only serve as an aid and a starting point, not as the ultimateobjective of vision.

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Calculation of lumi-nance L from the illumi-nance E and the reflec-tance R. The formulaonly applies in the caseof completely diffusereflection, but gene-rally produces goodapproximate values inpractice.

Simplified correlationbetween illuminance E,reflectance R and lumi-nance L in working places with visual task I,working surface A, ceiling D, wall W andpartition walls S.

EI = 500 lxEA = 500 lxED = 50 lxEW= 200 lxES = 200 lx

LI = 111 cd/m2

LA = 48 cd/m2

LD = 11 cd/m2

LW = 32 cd/m2

LS = 19 cd/m2

RI = 0,7RA = 0.3RD = 0.7RW= 0.5RS = 0.3

L = E . ®!

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0,2 0,4 0,6 0,8 1,0

200

300

400

500

L (cd/m2)

®

3.1 Lighting design concepts3.1.2 Luminance technology

lit countryside that gives rise to glare, but– in spite of its lower luminance factor –the pane of opal glass that prevents thisvery view; a blue summer sky with a fewclouds is not a source of glare, but the uni-form grey-white sky of a dull day inNovember.

If it is not possible the find an ab-stract definition for an “unstable” milieu,the attempt to describe ideal luminancepatterns out of context is unsound. Maxi-mum luminance contrast values of 1:3 or1:10 between the object of attention andthe proximate or broader ambient fieldhave been laid down that confine thelighting designer’s range of expression toa dull average. Phenomena such as brilli-ance and accentuated modelling, whichplay a considerable role in imparting infor-mation about materials in our environ-ment, are practically excluded; luminancesituations such as we experience on anysunny day or on a walk in the snow, areconsidered to be unreasonable. But you canonly decide whether a lighting situation is pleasing or unreasonable when you ex-perience a specific situation; luminancecontrasts on the beach are not too starkfor someone taking a stroll, but they will bother someone who is trying to reada book.

Just as the brightness we actuallyperceive cannot be derived from luminance,it is impossible to conclude the exactlighting conditions which are necessary toensure good perception simply by exami-ning the contrast range of a lit environ-ment; the lighting designer is obliged toexamine each specific situation, the infor-mation it provides and the perceptualrequirements of the users of the space.

The difficult aspect to evaluating thequality of lighting concepts is the excep-tionally vast adaptability of the humaneye: a perceptual apparatus that is able toprovide usable results at 0.1 lux on a clearnight or 100 000 lux on a sunny day, isnot substantially disturbed in its perfor-mance by luminance contrasts of 1:100,and is entirely capable of balancing the effects of inadequate lighting design. It is therefore not surprising that lightinginstallations that do not take into accountthe essential requirements of the percei-ving person generally meet with accep-tance. Dissatisfaction with the lighting ata workplace, for example, is frequentlynot recognised by the person concernedas a result of poor lighting design –criticism is usually aimed in the directionof the innocent “neon lamp”.

Progress made in the field of lightingdesign can therefore not be evaluated by simply differentiating between inade-quate and optimum, or clearly correct orincorrect lighting solutions. In the case ofthe lighting of workplaces a quantitativedesign concept may prove to be clearlysuccessful, even when the lighting isexclusively adjusted to optimising visual

Only with knowledge of the lighting con-ditions and with the aid of constancy phe-nomena can interpretations be made ofthe luminance pattern on the retina, anda familiar three-dimensional image arisefrom the mass of confusing parts. Thebrightness ratios that we actually perceivemay deviate considerably from the under-lying luminance pattern. In spite of itshigher luminance a grey, overcast sky seenabove a field of snow will appear to bedarker than the snow. The decline in lumi-nance over a wall surface lit from anangle is likewise ignored, whereas it hasan increased effect on the sides of a cube.Colour ratios and grey values are thuscorrected in differently lit areas, with theresult that we perceive a consistent scale.

In every case, the registering ofluminances is deferred in favour of theconstant qualities of objects, which isinherent to our perception: the acquisitonof information about a given environ-ment clearly has higher priority than mereoptical images. This central aspect of the way we process information cannot betaken into consideraion by a theory ofperception based on luminance, however.Similar to quantitative lighting design,luminance technology adheres to a purelyphysiological concept, which reduces the perceptual process to the creation ofoptical images in the eye, ignoring allother processes that take place beyondthe retina. The information content of ourperceived environment and the interestthis environment awakens in the perceivingbeing cannot be explained by this model -but it is this very interplay of informationand interests that allows the perceivedimage to be processed, the relativity ofluminances to be apprehended and theluminance patterns in the eye to be rein-forced or ignored.

If the aim of perception is to process in-formation, and if it takes place dependingon the information provided, it cannotunder any circumstances be examined irre-spective of the information contentprovided by or inherent in a specific en-vironment. In the light of this fact, anyattempt to define a set of general rulesfor lighting that are not based on aconcrete situation is of doubtful validity.This also applies to the attempt to makean abstract definition of “stable” lightingsituations, which is what luminance-based design strives to do.

A general definition of the conditionsrequired for the development of psycho-logical glare - the most extreme form ofan “unstable”, disturbing lighting situation- will fail due to the fact that the infor-mation content pertaining to the relevantglare sources is not available. It becomesapparent that glare does not only dependon stark luminance contrasts, but also on lack of information content with regardto the surface producing the glare. It isnot the window with a view over the sun-

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Preferred luminance Lfor visual tasks as afunction of reflectanceR of the visual task.The luminances prefer-red in the experimentare in proportion to thereflectance factor; theyresult when the illumi-nance level remainsconstant. Consequently,in the case of the per-ception of visual tasks, incomparison to lumi-nance, illuminance is aprime criterion.

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as an active factor in the perceptual process– an acting subject, who can construct an image of a visual environment based ona wide variety of expectations and needs.

Only when two main factors are cor-related – the structural information provi-ded by a visual environment and theneeds of a human being in the given si-tuation – does the so-called pattern ofsignificance of a space develop. Only thenis it possible to analyse the ranking of im-portance which relate to individual areasand functions. On the basis of this patternof significance it is possible to plan thelighting as the third variable factor in thevisual process and to design it accordingly.The need for orientation aids variesradically depending on the type of environ-ment – light applied for guiding peoplethrough spaces can be of prime importancein a congress centre with constantlychanging groups of visitors, whereas thistask is considerably less important infamiliar environments. The decision whetherto graze the surface structure of a wallwith light depends on whether this structurepresents essential information, e.g. aboutits character as a mediaeval stone wall orwhether such lighting will only reveal the poor quality of the plaster work.

Perception-oriented lighting design,which is directed at the human being andhis needs, can no longer be directed inprimarily quantitative terms relating toilluminance and the distribution of lumi-nance. To achieve lighting that is suitablefor a given situation it is necessary to de-velop a set of qualitative criteria, an entirevocabulary of terms, which can describethe requirements a lighting installationhas to meet and comprise the functions of the light with which these requirementscan be fulfilled.

performance. Luminance technology canalso be regarded as a step in the rightdirection; the expansion of the design analysis from the visual task to the entirespace and the development of zone-oriented lighting design all make for pro-gress, and in turn have a positive effecton the quality of the lighting.

Even if lighting solutions can beachieved using quantitative processes thatare acceptable within the broad spectrumof visual adaptability, it does not mean tosay that lighting has been designed thatwill comply with all essential perceptualrequirements. Both quantitative lightingdesign and luminance technology remainat the level of purely physiologicallyoriented design, which does not provideany reliable criteria apart from theisolated consideration of visual tasks.Luminance technology is equally not ableto keep both promises – the designer’sprediction of what the visual effect will beand the creation of (perceptually spea-king) optimum, “stable” lighting situations;it is therefore not realistic to lay down a set of abstract criteria for brightnessdistribution that do not relate to a specificsituation.

3.1.3 The principles of perception-oriented lighting design

The main reason for our dissatisfaction withlighting concepts based on quantitativelighting design or luminance technologyis the fact that they adhere strictly to a physiologically oriented view of humanperception. Man is only seen as a mobilebeing for processing images; his visualenvironment is reduced to the mere “visualtask”, at the best to an overall perceptualunderstanding of “table” and “wall”,“window” and “ceiling”. Seen from this angle,it is only possible to analyse a minorportion of the complex perceptual process,which comprises the eye and an abstractcomprehension of the world around us; noattention is paid to the person behind theeye and the significance of the perceivedobjects.

Only when we begin to go beyond thephysiology of the eye and take a closerlook at the psychology of perception canthe conditions required for the processingof visual information be fully understoodand all the factors involved in the correla-tion between the perceiving being, theperceived objects and light as a mediumfor allowing perception to take place be taken into account. In a concept that un-derstands perception as more than aprocess for handling information, the visualenvironment is more than just a configu-ration of optically effective surfaces. In thisway both information content and thestructures and aesthetic qualities of a pieceof architecture can be analysed ade-quately. Man is no longer seen as merelyrecording his visual environment, but

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3.1.3.1 Richard Kelly

A significant part of this task – a basicdescription of the various functions oflight as a medium for imparting informa-tion – was developed in the fiftiesby Richard Kelly, a pioneer of qualitativelighting design.

Kelly describes the first and basic form oflight as ambient light. This is the light thatprovides general illumination of our envi-ronment. It guarantees that the surroundingspace, plus the objects and persons in it,are visible. This form of overall, uniformlighting ensures that we can orient oursel-ves and carry out general tasks. It is co-vered to a large extent by the ideas under-lying quantitative lighting design, exceptthat ambient light in the Kelly sense is notthe aim of a lighting concept, but only abasis for further planning. The aim is not toproduce overall lighting of supposedlyoptimum illuminance, but differentiatedlighting that can be developed takingambient light as the basic level of lighting.

To achieve differentiation, a second formof lighting is required that Kelly refers toas focal glow. This is the first instancewhere light becomes an active participantin conveying information. One importantaspect that is taken into account here isthe fact that our attention is automati-cally drawn towards brightly lit areas. It istherefore possible to arrange the mass ofinformation contained in an environmentvia the appropriate distribution ofbrightness – areas containing essentialinformation can be emphasized by accentlighting, information of secondaryimportance or disturbing information toneddown by applying lower lighting levels.This facilitates the fast and accurate flowof information, the visual environment,with its inherent structures and the signi-ficance of the objects it contains, is easilyrecognised. This also applies to orientationwithin the space – e.g. the ability to distin-guish quickly between a main entranceand a side entrance – and for the accen-tuation of objects, as we find in productdisplays or the emphasizing of the mostvaluable sculpture in a collection.

The third form of light, play of brilliance isa result of the realization that light notonly draws our attention to information,but that it can represent informationin itself. This applies above all to speculareffects, such as those produced by pointlight sources on reflective or refractivematerials; the light source itself can alsobe considered to be brilliant. This “play of brilliance” can lend prestigious spaces inparticular life and atmosphere. The effectproduced traditionally by chandeliers andcandlelight can be achieved in modern-daylighting design through the purposeful ap-plication of light sculptures or the creationof brilliance from illuminated materials.

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Richard Kelly, one ofthe pioneers of modernlighting design. Inprojects designed by leading architects, e.g. Mies van der Rohe,Louis Kahn or PhilipJohnson, he developedthe basic principles ofdifferentiated lightingdesign, influenced bystage lighting.

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In his definition of biological needs Lampresumes that our attention is only de-dicated to one visual task in moments ofgreatest concentration. Man’s visualattention is almost always extended toobserve his entire surroundings. Anychanges are perceived immediately, beha-viour can be adjusted without delay toadapt to the changed situation.

The emotional evaluation of a visualenvironment does not only depend onwhether it provides the required informa-tion in a clear fashion or whether itwithholds it from the observer – the feelingof unease that arises in confusing situa-tions. We have all experienced the feelingof being disoriented in the mass of visualinformation at an airport or when lookingfor a specific office in a local authoritybuilding.

For Lam the first of the basic psychologicalneeds for environmental information isthe need for orientation. Orientation can beunderstood in this case first in a spatialsense. It refers to how well destinationsand routes can be identified: the spatiallocation of entrances, exits and what theenvironment specifically offers. Thismay be a reception, a special office or theindividual departments of a departmentstore. But orientation also comprises in-formation about further aspects ofthe environment, e.g. the time of day, theweather or what is happening around us. If this information is missing, as may bethe case in closed spaces in departmentstores or in the corridors of large buildings,for example, we feel the environment to be unnatural and even threatening; onlywhen we have left the building can wesuddenly make up for the informationdeficit – we establish that it has becomedark and started to rain, for example.

A second group of psychological needsis targeted at how well we can comprehendsurrounding structures. It is importantthat all areas of the spaces are sufficientlyvisible. This is a decisive factor in ourfeeling of security in a visual environment.If there are niches and corridors we can-not see into or parts of a space are poorlylit, we feel uncomfortable and unsafe.Dark corners, e.g. in subways or dark cor-ridors in hotels at night, may containdanger, in the same way as overlit areas.

Comprehension of our surroundingsdoes not mean that absolutely everythinghas to be visible, it comprises an elementof structuring, the need for a clearly struc-tured enviroment. We feel that a situa-tion is positive when the form and structureof the surrounding architecture is clearlyrecognizable, and when important areasare designed to stand out against thegiven background. Instead of a confusingand possibly inconsistent flow of infor-mation the space thus presents itself as a clearly structured whole.

3.1.3.2 William Lam

With his differentiation between the basicfunctions of light Kelly made a substan-tial contribution towards the theory behindqualitative lighting design. He provides a systematic presentation of the meansavailable. The question that still remainsopen is: according to what criteria arethese means to be applied? The lightingdesigner is obliged to continue to dependon his own instinct, experience andthe inadequate support provided by thequantitative criteria laid down in thestandards when it comes to analysing theparticular lighting context – determi-ning the special features of the space, howit is utilized and the requirements of theusers.

Two decades pass, however, beforeWilliam M. C. Lam compiles the missingcatalogue of criteria: systematic, context-related vocabulary for describing therequirements a lighting installation has tomeet. Lam, one of the most dedicatedadvocates of qualitative lighting design,distinguishes between two main groups of criteria.

He first describes the group of activityneeds: the needs for information relatedto specific conscious activities. To under-stand these needs it is essential to knowthe characteristics of the various visualtasks to be performed; analysing activityneeds is therefore in line with the criterialaid down for quantitative lighting. As far as the aims of lighting design are con-cerned, there is general agreement on this point; the aim is to design functionallighting that will provide optimum visualconditions for the specific task – be it work,movement through a space, or leisureactivities.

In contrast to the advocates ofquantitative lighting design Lam objects strongly to uniform lighting aligned tothe respective most difficult visual task;he proposes a far more differentiatedanalysis of all the activities that will takeplace according to location, type andfrequency.

Even more important than this new eva-luation of a group of criteria that alreadyexisted, is what Lam calls his secondcomplex, which comprises biological needs.In contrast to activity needs, which arederived from man’s occupations with spe-cific tasks, biological needs covers thepsychological need for information, themore fundamental aspects of the humanrelation to the visual environment.Whereas activity needs arise from specificconscious activities and are aimed at the functional aspects of a visual environ-ment, biological needs comprise mainlyunconscious needs, which allow us toevaluate a situation from an emotionalpoint of view. They are concerned with ourfeeling of wellbeing in a visual environment.

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William Lam, lightingdesigner and dedicatedtheoretician of quali-tative lighting design.

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architecture: in the form of a light struc-ture, an alignment of spotlights or a lightsculpture, the lighting installation itselfcan become an architectural element thatcan purposefully change the appearanceof the space.

When accentuating specific areas it is notonly visual tasks that traditionally receiveattention that should be underlined.A view outside or the presence of otherpoints of interest, e.g. a work of art, can be equally effective.

A third area consists of the balance be-tween man’s need for communication andhis right to clearly defined private spaces.Both extremes, complete isolation andcomplete public exposure, are felt to benegative; a space should promote contactto other persons, while at the same timeallowing private spaces to be defined. Aprivate space can be created by definingan area with light: a seated area or aconference table within a large room, forexample, and making it stand out from its surroundings.

3.1.3.3 Architecture and atmosphere

Both main groups of William Lam’s criteriadescribe man’s needs, his needs for afunctional and perceptually sound environ-ment. Besides this analysis, which is basedon the needs of man as a perceivingbeing, it must not be forgotten that lightand luminaires also make a substantialcontribution towards the aesthetic effectof architectural design. When Le Corbusierdescribes architecture as “the correct andmagnificent play of masses broughttogether in light”, he underlines the signi-ficance of lighting on the design of buil-dings.

Lam’s demand for a clearly structuredvisual environment comes very close tofulfilling this task, but does not cover allaspects. It is certainly possible to struc-ture a space according to the psychologicalneeds of the users by applying differentforms of lighting. Any decision to go forone of these approaches implies a de-cision to create a different aesthetic effect,a different atmosphere in the space.Apart from merely considering the needsof the perceiving being it is also necessaryto plan the interplay of light and archi-tecture.

As with user-oriented lighting design, lightalso has a supporting function in archi-tecture. It is a tool for rendering the givenarchitectural structures visible, and contri-butes towards their planned effect.Lighting can go beyond this subordinaterole and itself become an active compo-nent in the design of the space. This applies in the first place for light that isnot only able to render architecturevisible, but also to enhance the intended appearance. This applies primarily toluminaires and their arrangement. Lumi-naires can be discreetly integrated into the architecture – e.g. via recessed moun-ting in the ceiling. The fixture itself is not visible, it is only the light that has effect.But luminaires can also be added to

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3.2 Qualitative lighting design3.2.1 Project analysis

3.2.1 Project analysis

The basis for every lighting design conceptis an analysis of the project; the tasks thelighting is expected to fulfil, the conditionsand special features. A quantitative designconcept can follow the standards laiddown for a specific task to a large extent.Standards dictate the illuminance level,the degree of glare limitation, the luminouscolour and colour rendering. When itcomes to qualitative planning, it is necessaryto gain as much information as possibleabout the environment that is to be illumi-nated, how it is used, who will use it, andthe style of the architecture.

3.2.1.1 Utilisation of space

A central aspect of project analysis is thequestion of how the spaces that are to beilluminated are used; it is important toestablish what activity or activities takeplace in the environment, how often andhow important they are, if they are asso-ciated with specific parts of the space or specific periods of time.

This will first give rise to a series ofglobal answers that outline the lightingtask, will frequently also indicate standardstipulations, and form a framework forthe lighting design concept. This compre-hensive analysis of the task – e.g. thelighting of a sales space, an exhibition, anoffice space or the wide range of func-tions related to a hotel – gives rise to aseries of individual visual tasks, the characteristics of which must in turn alsobe analysed.

Two criteria relating to a visual taskare the size and contrast of the detailsthat have to be recorded or handled; therethen follows the question of whethercolour or surface structure of the visual taskare significant, whether movement andspatial arrangement have to be recognizedor whether reflected glare is likely tobe problem. The position of the visual taskwithin the space and the predominantdirection of view may also become centralissues – visibility and glare limitationhave to be handled differently in differentenvironments. In a gymnasium, forexample, the direction of view of peopleplaying volleyball is upwards, or in an art gallery on the vertical, or for visualtasks in offices on the horizontal.

Apart from the qualities of the illumi-nated objects the visual performance ofthe user must also be taken into account,especially in the case of older people –the eye becomes less efficient with age, andolder people are more sensitive to glare.In individual cases, the lighting of oldpeople’s homes in particular, special atten-tion must be paid to these increaseddemands on illuminance and glare limita-tion.

Light plays a central and manifold role inthe design of a visual environment. Workand movement are only possible when we have light to see by; architecture, peopleand objects are only visible if there islight. Apart from simply making our sur-roundings visible light determines theway we perceive an environment, influen-ces the way we feel and the aestheticeffect and atmosphere in a space. You onlyhave to enter a Baroque church with itsbright and inspiring atmosphere to seeand feel what effects light can have in ar-chitecture, or, to the other extreme, look at Piranesi’s paintings of dungeons withtheir dark labyrinths, where the shadowsconceal a never-ending source of horror.

Due to the adaptability of the eye ele-mentary perception can take place atminimum lighting levels or under difficultvisual conditions, while for optimum con-ditions at the workplace and for a piece ofarchitecture to be accepted and found tobe aesthetically pleasing it is necessary tocreate lighting whose qualities, illumi-nance and luminance distribution are inharmony with the particular situation.

One of the most frequent sources oferror in lighting design is to separate lightfrom its complex associations with hu-man psychology and human activities aswell as with the surrounding architecture.Simplified, unilateral lighting design canprovide easily compehensible concepts, butoften leads to unsatisfactory results byoverlooking essential aspects. This appliesto both purely quantitative lighting de-sign, which might produce optimum wor-king conditions but forgets the perceivingbeing, and to primarily design-orientedlighting, which furnishes spaces withstylish luminaires without regard for thelighting effects these fixtures produce.

What is really required is lighting design that meets all the lighting require-ments – design concepts that form an integral part of the overall architecturaldesign and produce a visual environmentthat supports various activities, promotesa feeling of well-being and is in line withthe architectural design. The quantitativedesign approach with its scientificallysound caculations and processes is actuallya great help here; when designing lightingfor workplaces this planning process itselfmay even become the primary objective.The main criterion for lighting design isnever a figure displayed on measuringequipment, but the human being – the de-ciding factor is not the quantity of light,but the quality, the way a lighting schememeets the visual needs of the perceivingperson.

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Three-circuit track formains voltage: lumi-naires for mains voltageand low-voltage fix-tures with an integraltransformer can beoperated on track;three separate groupsof luminaires can be switched or dimmed.

Spotlights for low-voltage halogen lampswith integral electronictransformer.

Washlights for double-ended halogen lamps,washlight for metalhalide lamps with inte-gral control gear, wall-washer for double-ended halogen lamps.

Spotlights for low-voltage halogen lampswith adjustable lightheads on an electronictransformer. Compactelectronic transformersallow the design of especially small lumi-naires.

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Spotlight for low-voltage halogen lampswith integral, conven-tional transformer.

Uplighter for compactfluorescent lamps or halogen lamps.

Spotlight for low-voltage halogen lamps.The extremely small dimensions of thelamp and the use of anexternal transformer allow the design ofcompact spotlights. Larger reflectors makefor enhanced opticalcontrol and increasedluminous intensity.

Low-voltage track:low-voltage spotlightswithout transformerscan be operated on thetrack. Power supply iseffected via an externaltransformer.

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3.2.1.3 Architecture and atmosphere

Besides the requirements that arise fromhow a space is used and the needs of theusers, lighting design also has to addressthe requirements of architecture and atmosphere. In the first place the archi-tectural building is regarded as an object of lighting – it is to be rendered visible, itsqualities accentuated, its atmosphereunderlined, and if necessary its effect modi-fied. Furthermore, the architectural con-cept also defines the basic conditions forthe design of user-oriented lighting.

Detailed information about the archi-tecture is of particular importance for thedesign of demanding lighting. This prima-rily concerns the overall architecturalconcept – the atmosphere the buildingcreates, the intended effect indoorsand out by day and night, the utlizationof daylight, and the question of budgetand the permissible energy consumption.

Along with this basic information about the project, the structures and qua-lities of the building itself are important.Quantitative lighting design also requiresinformation about the dimensions of the spaces to be lit, the type of ceiling andthe reflectance of the room surfaces.Other factors to be taken into considera-tion are the materials applied, colourscheme and planned furnishings.

As in the case of a clearly structuredenvironment, architectural lighting isconcerned with lighting that underlinesthe structures and characteristic featuresof the building, not only from the pointof view of optimised perception, butinvolving the aesthetic effect of the illumi-nated space. The special features andmain characteristics of an environmentalso present an important issue, above allthe question of the formal language ofthe building – the design of the spaces andhow they are subdivided, what modulesand rhythms they contain, and how lightand luminaires are to be aligned tounderline these aspects.

3.2.1.2 Psychological requirements

Besides the objective requirements whichresult from the activities performed in avisual environment, attention must also bepaid to the demands that stem from theusers themselves. Many of these are con-cerned with the possibility of gainingbetter views of their surroundings. Thisapplies to the need for information abouttime of day and weather, about what isgoing on in the rest of the building, andsometimes also the need for orientationwithin the environment. One special case isthe utilisation of sunlight in atriums orthrough skylights and light wells. The lat-ter do not necessarily offer a view outsidebut do provide information about theweather and the progress of time is main-tained – a changing patch of sunlightcan contribute to the feeling of life insidea building.

Apart from the need for daylight andviews outside, which depends on the indi-vidual project to a large extent, there is a changing need for orientation aids. In ex-tensive buildings, where there are conti-nually different groups of users, the needfor optical systems that guide peoplethrough spaces becomes a central issue. Insome cases it is only necessary to under-line a number of focal locations. In buildingswith simple spatial structures that areconstantly in use the need for orientationaids is of secondary importance. It istherefore essential to find out how impor-tant the need for orientation is in eachspecific case and which routes and areasdemand special attention.

Another psychological need that hasto be fulfilled is the creation of a clearlystructured environment. This is especiallyimportant in areas that are potentiallysubjected to danger, i.e. where the struc-ture of the space must be easily legible.In general, it can be said that a clearlystructured environment contributes to our feeling of well-being in a visual environ-ment. In reality this means accentuatingthe structure of the space, the materialsapplied and the most significant parts ofthe space, and above all the type and ar-rangement of the room limits that are tobe illuminated and the information signsthat are to be emphasized.

The last factor is the need for definedspatial zones; the expectation that youcan recognize and distinguish betweenareas with different functions from thelighting they receive. This mainly concernsthe lighting of functional areas that weaccept as typical and which is in line withprevious experience, e.g. the application of higher colour temperatures and uni-form, diffuse lighting in working spaces,but warmer, directed light in prestigiousspaces. The need for clearly defined privateareas also falls in this category; lightingcan be applied especially effectively in theconversation areas or waiting zones within larger spaces to create a feeling ofprivacy.

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design must submit to acoustic engineeringrequirements or whether integral solu-tions, e.g. a combination of lighting andan air-handling system, are possible.

The real challenge behind qualitativelighting design lies in the development ofa concept that is able to fulfil a widerange of requirements by means of alighting installation that is both techni-cally and aesthetically consistent. In con-trast to quantitative concepts, whichderive one general set of lighting qualitiesfrom the given profile of requirements for a project, which almost inevitably leadsto a uniform and thereby standard designusing light and luminaires, qualitativelighting design must come to terms withcomplex patterns of required lightingqualities. This cannot mean, however, thatthe designer responds to an unstructuredset of lighting requirements with anequally unstructured variety of luminaires.The well-meant consideration of a widerange of lighting tasks frequently leads toan unsystematic distribution of a widevariety of luminaire types or to a conglo-meration of several lighting systems. Such a solution may provide an adequatedistribution of lighting qualities, but thevalue of such costly installations from thepoint of view of perceptual psychologyand aesthetics is questionable owing to thelack of harmony on the ceiling.

From a technical, economic and designpoint of view the aim of lighting designshould be to find a solution that does notgo for the overall uniform lighting effectand equally not for a confusing anddistracting muddle of lighting fixtures de-signed to cover a wide variety of lightingrequirements, but a concept that producesa clearly structured distribution oflighting qualities by means of a consistentlighting scheme. The degree of complexitythat has to be accepted depends on the specific lighting task. It may be thatthe main requirements set by the lightingtask allow general lighting throughoutthe space, or that differentiated lightingcan be achieved using integral systemssuch as light structures or the comprehen-sive range of recessed ceiling luminaires.Or in a multifuntional space that a combi-nation of different luminaire systems may be necessary. Nevertheless, the mostconvincing solution is a concept thatachieves the required result with the leastamount of technical equipment and thehighest degree of design clarity.

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3.2.2 Project development

The result of the project analysis is a se-ries of lighting tasks that are allocated tospecific areas within the space or specifictimes of day, all of which form a charac-teristic matrix of requirements for a visualenvironment. The next phase followingthe project analysis is the development ofa qualitative concept that outlines anidea of the qualities the lighting shouldpossess, without giving exact informationas to the choice of lamps and luminairesor how they are to be arranged.

The first task concept development has todeal with is the allocation of specificlighting qualities to the lighting tasks de-fined as a result of the project analysis; todefine the lighting conditions that are tobe achieved in specific locations at specific times. To begin with, this concerns thequantity and the various other criteria ofthe light in the individual areas, plusthe order of importance of these individualaspects within the overall lighting con-cept.

The pattern of requirements acquiredin the course of the project analysis thusgives rise to a pattern of lighting quali-ties, which in turn provides informationabout the various forms of lighting and the required spatial and temporal diffe-rentiation. This is the first indication of whether the lighting is to be uniform ordifferentiated to match different areas,whether the lighting installation is to befixed or flexible and whether it is a goodidea to include lighting control equipmentfor time-related or user-related lightingcontrol.

The allocation of lighting qualities to the individual lighting tasks in a projectgives rise to a catalogue of design objec-tives, which takes into account the differentrequirements the lighting has to fulfil,without consideration for the conditionsrequired to realise the lighting scheme orinstructions on how to effect a consistentlighting design concept.

A practice-oriented design conceptmust therefore first describe how thedesired lighting effects can be realisedwithin the basic conditions and restrictionsinherent to the project. The design con-cept may be required to correspond tospecific standards, and it must keep withinthe budget with regard to both theinvestment costs and the operating costs.The lighting concept must also be coordi-nated with other engineering work to beeffected on the project, i.e. air-conditio-ning and acoustics, and, of course, har-monize with the architecture. It is impor-tant to clarify the significance ofindividual aspects of the lighting for theoverall concept; whether one particularform of lighting can justify preferentialtreatment, e.g. the demand for adequateroom height in the case of an indirectlighting installation, whether the lighting

Example of the develop-ment of a differentiatedlighting concept (from thetop downwards): generallighting provided by down-lights in accordance withthe identified visual tasks,supplemented by wall-washers for the architectu-ral lighting and track-mounted spots for the accentuation of specialfeatures.

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Lighting for the restau-rant beneath the domeof the atrium. Wall-mounted luminaires (1) provide both indirectlighting of the domeand direct lighting ofthe restaurant.

Pendant luminaires (2)with a decorativecomponent continuethe direct lighting in the restaurant insidethe actual space.

Lighting of the cafe-teria. A ceiling-moun-ted luminaire (3)provides uniformlighting over this level.

The lighting compo-nents for the generallighting in the atrium(4) are mounted onpillars on the walls ofthe atrium. They radiatelight upwards. The lightis then reflected byceiling reflectors or by theatrium ceiling, therebyproviding indirectlighting. The pillars aresimultaneously accen-tuated by grazing lightdirected downwards.

Individual architecturalelements, e.g. the balastrades of the ad-joining sales floors, the lift car, the upperwall of the lift shaftand the opening of theatrium are accentuatedby a decorative, linearlighting components(6).

The free-standing pan-oramic lift is accentu-ated by grazing lightfrom below (5).

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Development of alighting concept forthe atrium of a largedepartment store. The representationsshow two vertical sec-tions set at right anglesto each other throughthe atrium with a cen-tral panoramic lift. The aim of a lightingconcept is to deter-mine the positions ofthe luminaires and thelighting quality, with-out defining luminairetypes or illuminancelevels.

The walkways leadingfrom the individual sales floors to the liftsreceive a curtain oflight from the directluminaires arrangedclosely together alongthe wall (7).

A series of recessedceiling downlights (8)provide generallighting in the adjoining sales spaces.

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3.3 Practical planning3.3.1 Lamp selection

Having completed the project analysisand developed a lighting concept the nextphase entails practical planning: decisions regarding the lamps and lumi-naires to be used, the arrangement and installation of the luminaires, theircontrol gear and the lighting controlequipment required. A detailed design canbe developed from a concept basedprimarily on lighting qualities, which willallow both illuminances and costs tobe calculated to a reliable degree.

Similar to the earlier planning phases,it is also not possible at this stage inthe planning process to stipulate a fixedor standard sequence of planning steps - it may be possible to decide on a lamp type at the beginning of a project, but it mayequally not be possible until an advancedstage in the planning process; thelighting layout may be the consequenceof the choice of a particular luminaire or, alternatively, the basis for the choice ofluminaire. Lighting design should be re-garded as a cyclical process, which alwaysallows the solutions that have beendeveloped to be aligned to the statedrequirements.

3.3.1 Lamp selection

The choice of light sources has a decisiveinfluence on the qualities of a lightinginstallation. This applies first and foremostto the technical aspects of the lighting;the costs for control gear that may be re-quired, the possibility of incorporating alighting control system and, above all, theoperating costs for the lighting installa-tion, depend almost entirely on the choiceof lamps. It also applies similarly tothe quality of light the lighting designeris aiming to achieve, e. g. the choice of luminous colour to create the atmospherein specific spaces, the quality of colourrendering or the brilliance and modellingnecessary for display lighting. The effect of the lighting does not depend solely onthe decision to use a specific lamp type,however; it is the result of the correlationof lamp, luminaire and illuminated envi-ronment. Nevertheless, the majority oflighting qualities can only be achievedwith the correct choice of light source. Itis just as impossible to create accentlighting using fluorescent lamps as it is toobtain acceptable colour rendering undersodium lamps.

The decision to select a particularlight source is therefore not to be takenlightly, but is dependent on the criteriadefined by the required lighting effect andbasic conditions pertaining to the project.From the wide range of lamp types availablethere will only be a limited numberwhich will fulfil the specific requirements.

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3.3

Wallwashers equippedwith (from the top downwards) halogenlamps, metal halidelamps and compactfluorescent lamps: thesame luminaire types with identicaldistribution characteri-stics produce differentluminous flux, lumi-nous colour and colourrendering qualitiesdepending on the lampused.

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3.3 Practical planning3.3.1 Lamp selection

vely independent of the luminous fluxemitted by the lamp.In contrast to lighting that produces mo-delling effects, brilliance does not requirethe light to be directed from one particu-lar direction. It only requires the lamps tobe point light sources. It is therefore not necessary to control the light usingreflectors - exposed light sources can be used to create brilliance, in which casethe light source itself and its effect onthe illuminated material is perceived asbeing brilliant.

Low-voltage halogen lamps are primarilyused for the creation of brilliance, as theyare extremely compact light sources withhigh luminance. Metal halide lamps canalso be used to produce brilliance, al-though their high luminous power mayundermine the creation of specular effects because the overall environment isgenerally brighter.

Brilliance can also be produced byclear versions of halogen lamps for mainsvoltage. Larger light sources with light-diffusing surfaces, such as frosted incan-descent lamps are less suitable, fluore-scent lamps and compact fluorescent lampsnot suitable at all.

3.3.1.2. Colour rendering

A light source can be said to have goodcolour rendering properties when thereare only slight deviations in colour be-tween a comprehensive range of coloursilluminated by the lamp in comparison to a standardised reference light source ofa corresponding colour temperature. Anystatement made or data given on colourrendering therefore refers to a specificcolour temperature. A colour renderingvalue that is valid for all luminous coloursdoes not exist. Colour rendering is an im-portant factor in lighting projects whereit is important to be able to judge thequality and effect of colours, e. g. formatching colours, for the lighting of worksof art or for the presentation of textiles.There are standards that stipulate theminimum colour rendering requirementsfor the lighting of workplaces.The colour rendering quality of a lightsource depends on the composition of thespecific lamp spectrum. A continuousspectrum provides optimum colour ren-dering, whereas line or band spectrumsmean poorer colour rendering. The spectraldistribution of the light is also of sig-nificance for colour rendering. Spectraldistribution that differs from that of thereference light source will also have adeteriorating effect on colour rendering values due to the fact that only specificcolour effects are emphasized.The highest colour rendering index (Ra 100),i. e. colour rendering category 1A, isobtained from all forms of incandescentlamps, including halogen lamps, sincethey represent the reference light source

3.3.1.1.Modelling and brilliance

Modelling and brilliance are effects thatcan be most easily achieved using directedlight. Compact light sources are the mostsuitable, as their light intensity can be in-creased significantly by using reflectors.

The modelling of three-dimensionalobjects and surfaces is emphasized by theshadows and luminance patterns produ-ced by directed light. Modelling is requiredwhen the material qualities emphasized(spatial form and surface structure) havean informative value - be it to check the quality of the material itself, for thelighting of a sculpture, the presentationof goods or the illumination of interestinglystructured room surfaces.

Modelling can only be effected bydirected light coming predominantly fromone direction. To produce modelling effects it is therefore only possible using effectively point light sources, where the intensity of light is frequently increasedusing reflectors or other control systems.For this reason the first choice is compactlamps with rotationally symmetrical re-flector systems. Linear light sources are notsuitable for producing modelling, thelonger the lamp, the less suitable it is, sincethe significant diffuse component ligh-tens shadows.

If extremely dramatic modelling is requi-red in confined areas low-voltage halogenlamps, which are very compact in form,are usually the most appropriate or, if in-creased luminous power is required, thenmetal halide lamps. To produce modellingeffects there are a variety of compactlamp types which can be used: from generalservice lamps, reflector lamps andhalogen lamps for mains voltage to high-pressure discharge lamps, whereby themodelling effect will inevitably be reducedas the size of the light source increases.Compact fluorescent lamps can produce areasonable degree of modelling, e.g. when they are used in downlights. Conver-sely, linear fluorescent lamps producepredominantly diffuse light.

Brilliance is produced by points of light of extremely high luminance. These maybe the light sources themselves, butbrilliance is also produced when the lightsources are reflected on glossy surfaces orwhen the light is refracted in transparentmaterials. Specular effects are frequentlyapplied in display lighting or in presti-gious environments to emphasize thetransparency or sparkling quality of theilluminated materials to enhance theirvalue or to create a festive atmosphere.Producing brilliance and specular effectsdemands more from the light source thanproducing modelling effects: it requiresconcentrated, practically point light sources.The sparkling effect depends predomi-nantly on the lamp luminance. It is relati-

127

Wallwashers for flu-orescent lamps (above)and halogen lamps(below). Uniform wall-washing can beachieved with the dif-fuse light produced by the fluorescent lampsor with the directedlight from the halogenlamps.

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for the warm white range. De-Luxe ver-sions of fluorescent lamps, plus some me-tal halide lamps have a colour renderingindex above 90 and are classified as colourrendering category 1A. The remainingfluorescent lamps and metal halide lampsare classified as colour rendering category1B or, as the luminous efficacy increasesat the expense of colour rendition, fallinto colour rendering categories 2A or 2B.High-pressure mercury and sodiumlamps with enhanced colour rendering areclassified at category 2B, with standardversions classified as category 3. Category4 only contains low-pressure sodiumlamps.

3.3.1.3 Luminous colour and colourtemperature

Similar to colour rendering, the luminouscolour of a light source is dependent onthe spectral distribution of the light emit-ted by the lamp. In the case of incandes-cent lamps this distribution is a result ofthe temperature of the filament, hencethe reference to colour temperature. In thecase of discharge lamps, however, a com-parative value must be used as a guideline- the most similar colour temperature. In practice it is not customary to provideexact colour temperature data. Luminouscolour is roughly categorized into warmwhite, neutral white and daylight white.Through the specific combination of lumi-nous substances it is possible, in the caseof discharge lamps, to create a furtherrange of special luminous colours, whichcannot be adequately described usingcolour temperature classification.

The luminous colour of a lamp affectsthe colour spectrum of illuminated ob-jects. Warm white lamps emphasize the redand yellow ranges of the spectrum, day-light white the blue and green, i. e. coldcolours. Luminous colour can be applied asa design factor for the presentation ofobjects which have defined colour ranges,for example. Some luminous colours areexpressly blended for the presentation ofspecific types of articles. Luminous colour also affects our subjective appre-ciation of a lighting situation; colderluminous colours at high illuminances andfrom diffuse lighting are comparable to the light of the sky, warm colour ap-pearances at lower illuminances in theform of directed light are comparable tocandlelight and considered to be pleasant.Recommended luminous colours are in-cluded in the published standards for thelighting of workplaces.

Light sources with exclusively warm whiteluminous colour comprise all forms of incandescent lamps plus high-pressuresodium lamps. There are also fluore-scent lamps, metal halide lamps and high-pressure mercury lamps available that are classified as being warm white. Light

3.3 Practical planning3.3.1 Lamp selection

sources with neutral white luminouscolour include fluorescent lamps, metalhalide lamps and high-pressure mercurylamps. Daylight white light sources in-clude fluorescent lamps and metal halidelamps. Fluorescent lamps are the onlylight sources available in special luminouscolours. The luminous colour of a lampcan, in fact, be manipulated, either byproviding the outer envelope with a specialcoating, as is the case for daylightquality incandescent lamps, or by apply-ing a conversion filter.

3.3.1.4 Luminous flux

The luminous flux of a lamp is especiallyimportant if the number of lamps withwhich the lighting is to be created hasbeen predetermined. It may be that the lighting is being designed using only afew high output lamps, or that a largenumber of low light output lamps are tobe used. The objective is not to select afew lamps of average luminous intensity,but to vary between large and small “lumen packages”. Low-voltage halogenlamps, conventional incandescent lampsand compact fluorecent lamps are exam-ples of small lumen packages. Halogenlamps for mains voltage, fluorescentlamps and high-pressure discharge lampshave higher luminous power. Metal halide lamps have the highest values.

3.3.1.5 Efficiency

The efficiency of a lighting installationdepends largely on the choice of lamps.The influence of other aspects, e.g. thechoice of control gear and control equip-ment is of less importance. When selec-ting lamps on the basis of their efficiencythere are a number of criteria that may be of primary importance, irrespective ofthe basic conditions inherent in thelighting task.

The luminous efficacy of a lamp is impor-tant when maximum luminous power,and illuminance, is to be achieved using aminimum of electric power. Incandescentlamps and halogen lamps have the lowestluminous efficacy at around 10-20 lm/w.The luminous efficacy of fluorescent lamps,high-pressure mercury lamps and metalhalide lamps is higher at 40-100 lm/w. Theexceptionally high luminous efficacy ofsodium lamps (up to 130 lm/w in the caseof high-pressure lamps) is achieved at the expense of colour rendering.

The rated life of a lamp is always importantwhen maintenance of the lightinginstallation results in considerable expenseor if conditions make maintenancedifficult, e. g. in the case of particularlyhigh ceilings or in rooms that are incontinual use. The rated life of incandescent

128

Colour rendering cat. ApplicationsQuality1A Textile, paint andOptimum printing industry

Prestigious spacesMuseums

1B Meeting roomsVery good Hotels

RestaurantsShop windows

2A Administration buildingsGood Schools

Sales spaces

2B Industrial manufacturingAcceptable plants

Circulation zones

3 Exterior lightingAdequate Warehouses4 Industrial hallsLow Exterior lighting

Floodlighting

Allocation of colourrendering categories inaccordance with theCIE and the colour ren-dering qualities oflamps and their typicallighting tasks.

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A, R, PARQTQT-LVTTCLSTHMT, HMEHIT, HIEHST, HSE

100 200 300 400 500P (W)

A, R, PARQTQT-LVTTCLSTHMT, HMEHIT, HIEHST, HSE

12020 40 80 100 14060 æ (lm/W)

A, R, PARQTQT-LVTTCLSTHMT, HMEHIT, HIEHST, HSE

2000 4000 6000 8000 10000t (h)

A, R, PARQTQT-LVTTCLSTHMT, HMEHIT, HIEHST, HSE

5000 TF (K)400030002000

A, R, PARQTQT-LVTTCLSTHMT, HMEHIT, HIEHST, HSE

20 40 60 80 100 Ra

3.3 Practical planning3.3.1 Lamp selection

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Colour rendering indexRa ranges for variouslamp types.

Colour temperatureranges TF for variouslamp types.

Service life t of various lamp types.

Range of power P forvarious lamp types.

Ranges of luminous efficacy h for variouslamp types.

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lamps is given as the average lamp life af-ter the failure of 50 % of the lamps; inthe case of discharge lamps the values referto lamp life in terms of light output, i.e.when there is a reduction in luminous fluxof up to 80 %. The actual rated life is,however, also affected by site conditions.In the case of incandescent lamps theoperating voltage has a critical influenceon the life of the lamp. In the case ofdischarge lamps it is switching frequencythat affects the rated life.

Incandescent lamps and halogenlamps have the shortest rated life at 1000 - 3000 h. The rated life of fluorescentlamps and metal halide lamps is con-siderably higher at 8000 h and 6000 h, respectively. Sodium lamps have a ratedlife of 10 000 h, high-pressure mercurylamps over 8000 h.

Lamp costs are another aspect of theefficiency of a lighting installation. Theyvary between values that can be ignoredwhen compared with costs for power andmaintenance, to values that are as high as these costs. The most economical lampsare conventional incandescent lamps,followed by fluorescent lamps and halogenlamps. Prices for high-pressure dis-charge lamps are substantially higher.

3.3.1.6 Brightness control

The dimming quality of light sources isimportant for the lighting of spaces withchanging activities and for environmentswhere different atmospheres are required.Dimmable lamps can also be used to ad-just the lighting to changing environmentalconditions, e. g. day and night-timelighting.

Conventional incandescent lamps andhalogen lamps for mains voltage can bedimmed easily and economically. Low-voltage halogen lamps and fluorescentlamps are technically more difficult to handle, but are also dimmable. From atechnical point of view high-pressuredischarge lamps should not be dimmed.

3.3 Practical planning3.3.1 Lamp selection

3.3.1.7 Ignition and re-ignition

Lamp behaviour when lamps are switchedon and reswitching after power failuremay be of significance in the design. Formany applications it is essential that thelight sources provide sufficient luminousflux immediately after switching (e.g.when a person enters a room). In the ma-jority of cases there is no time to allow a cooling phase before reigniting lampsthat have been switched off or are offdue to power failure. For the lighting oflarge meeting spaces and sports facilitiesthere are statutory requirements stipula-ting that the instant re-ignition of lampsmust be ensured.Incandescent lamps and halogen lampspose no problems here. They can simply beswitched on at any time. The same appliesto fluorescent lamps, which can be ignitedin a cold or warm state with negligibledelay. High-pressure discharge lampsrequire a substantial run-up period. Re-ignition is only possible without specialequipment, after a specific cooling time.If high-pressure lamps are to allow in-stant re-ignition, double-ended versionsequipped with special ignitors must beinstalled.

3.3.1.8 Radiant and thermal load

When dimensioning air-conditioning plantsthe lighting load has to be taken intoaccount. This is due to the fact that thepower used by the lighting equipment is, in fact, converted into heat, either di-rectly through air convection or whenlight-absorbing materials heat up. Thethermal load of a space increases, the lower the efficacy of the light sources, sincein the case of low efficacy for a givenlighting level more energy exists in theinfrared range.

In the case of some special lighting taskslimiting the radiant load on objects is a prime concern. This applies to accentlighting on heat-sensitive objects. Radia-tion problems occur most frequently inexhibition lighting, however. In the exhi-bition environment light, infrared and ultraviolet radiation, can all result in da-mage due to the acceleration in theageing of materials and fading of colours.

High proportions of infrared radiation andconvection heat are emitted by lightsources with predominantly low luminousefficacy, such as incandescent lamps andhalogen lamps. In the case of linear andcompact fluorescent lamps infraredradiation is considerably lower.

Ultraviolet radiation is theoreticallyemitted predominantly by high-pressuredischarge lamps. As the UV component is always reduced by obligatory front glasscovers, the highest ultrviolet load inpractice is produced by halogen lamps which

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Formula for calculatingthe operating costs ofa lighting installationon the basis of specificlamp costs K (DM/106

Imh). To calculate thecosts the lamp priceKLa, the wattage P, theluminous flux Ï, the

service life t and the cost per unit of electri-city a are required. De-pending on lamp typeand power the specificcosts can be betweenDM 3 and DM 30 per106 Imh.

[K = ( + ) . 106P . aÏ . 1000

KLaÏ . t

[K] = DM106 lm . h

[a] = DMkW . h

[KLA] = DM[P] = W[Ï] = lm[t] = h

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3.3 Practical planning3.3.1 Lamp selection

131

Relative damage factorD of optical radiationas a function of wave-length l. Damagedecreases exponenti-ally through the wave-lengths including themajority of the rangeof visible radiation.

Correlation of the irra-diance Ee on an exhibitat a given illuminanceE and the relative radiation peformanceof a lamp Ïe.

Wavelength ranges ofultraviolet radiation(UV), visible radiation(light) and infraredradiation (IR). UV andIR radiation are furthersubdivided into A, Band C categories, inaccordance with DIN5031 Part 7.

Relative radiation fluxÏe of different lamp types in relation to aluminous flux of 103

Im, classified accordingto the different wave-length ranges:UV (280 nm-380 nm),light (380 nm-780 nm),IR (780 nm-10000nm).

Range of exposure H asthe product of illumi-nance E (klx) and expo-sure time t (h) for thevisible fading of an ex-hibit as a function ofthe light fastness S ofthe exhibit ( in accor-dance with DIN 54004)and the type of lightsource used. The uppertolerance curve appliesto incandescent lamps,

the lower one to day-light. Halogen lampsand discharge lamps liewithin the band. Exam-ple: an exhibit classifiedas light fastness cate-gory 5 shows initialevidence of fading af-ter approx. 1200 klxhunder daylight, afterapprox. 4800 klxh un-der incandescent light.

Optical radiation l (nm)

UV-C 100 ≤ l < 280UV-B 280 ≤ l < 315UV-A 315 ≤ l < 380

Light 380 ≤ l < 780

IR-A 780 ≤ l < 1400IR-B 1400 ≤ l < 3000IR-C 3000 ≤ l < 10000

Lamp Ïe (W/klm)UV Light IR

A, R, PAR 0.05–0.10 5–7 35–60QT 0.10–0.15 5–6 25–30T, TC 0.05–0.15 3–5 6–10HME 0.20–1.00 2–3 10–15HIT 0.20–1.00 2–5 6–10HSE 0.01–0.05 2–3 4–6

100

50

20

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2

300 350 400 450 500 550

D (%)

¬ (nm)

10000

1000

2000

3000

4000

5000

6000

7000

8000

9000

1 2 3 4 5 6 7 8

H (klx . h)

S

[Ee = Ïe . E1000

[E] = lx

[Ïe] = Wklm

[Ee] = Wm2

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do not have an outer envelope. They emitminimal ultraviolet radiation, emittingthis freely through their quartz glass outerenvelopes. Disturbing infrared or ultra-violet components produced by the selectedlamps can in practice be reduced sub-stantially through the use of suitable re-flectors or filters.

Both infrared and ultraviolet radiation loadon persons or objects produced by lightsources used for interior lighting is negli-gible. The limit set for connected load is approximately 50W/m2, above which theeffect of the thermal load will have anoticable effect on the subjective feelingof well-being in the local area.

An exception exists in the case of specialfluorescent lamps, so-called “full spec-trum lamps”, whose spectral distributionis very similar to the global radiation ofthe sun and daylight, producing a “natural”light. The UV and infrared components are increased at the expense of the visibleradiation. There is no documentaryevidence on the advantages of these lampswith regard to health or technical bene-fits in the quality of light.

3.3.2 Luminaire selection

The choice of light sources outlines thetechnical qualities of the lighting designconcept and the limits to the lightingqualities that can be achieved. The light-ing effects that can be obtained withinthis range depend on the choice of lumi-naires in which the lamps are to be used.The choice of lamp and luminaire is there-fore closely related. Opting for a parti-cular light source will reduce the choiceof luminaire, and vice versa, the choice of luminaire will restrict the choice oflamp.

3.3.2.1 Standard product or custom design

In most cases the choice of luminaireswill be confined to the standard productsavailable, because they can be supplied at reasonably short notice, have clearly de-fined performance characteristics andhave been tested for safety. Standard lumi-naires can also be used in special con-structions, such as lighting installationsthat are integrated into the architecture(e.g. cove lighting or luminous ceilings).In the case of large-scale, prestigious pro-jects consideration may also be givento developing a custom designed solutionor even a new luminaire. This allowsthe aesthetic arrangement of luminaires inarchitecture or in a characteristicallydesigned interior and the solution of spe-cific lighting tasks to be effected incloser relation to the project than if onlystandard products are chosen.

3.3 Practical planning3.3.2 Luminaire selection

Additional costs for development andtime considerations must be included inthe calculation of overall costs for theproject.

3.3.2.2 Integral or additive lighting

There are two basic contrasting conceptsfor the arrangement of luminaires in an architectural space, which can allocatedifferent aesthetic functions to thelighting installation and provide a rangeof lighting possibilities. On the onehand, there is the attempt to integrate theluminaires into the architecture as far as possible, and on the other hand, the ideaof adding the luminaires to the existingarchitecture as an element in their ownright. These two concepts should not beregarded as two completely separateideas, however. They are the two extremesat either end of a scale of design andtechnical possibilities, which also allowsmixed concepts and solutions.

In the case of integral lighting theluminaires are concealed within the archi-tecture. The luminaires are only visiblethrough the pattern of their apertures.The planning does not focus on theapplication of the luminaires themselvesas design elements, but on the lightingeffects produced by the luminaires. Integrallighting can easily be applied in a varietyof environments and makes it possible tocoordinate luminaires entirely with thedesign of the space.

Integral lighting generally presents acomparatively static solution. The lightingcan only be changed using a lightingcontrol system or applying adjustable lumi-naires. There are therefore limits to adap-ting integral lighting to meet the changinguses of a space. Integral lighting alsorequires certain conditions relating to theinstallation. This may mean a suspendedceiling to allow recessed mounting, or theprovision of apertures for recessedmounting into ceilings or walls in newbuildings. The most extreme cases areforms of lighting that use architecturalelements to create lighting effects. These include luminous ceilings, cove ligh-ting or backlit elements.Recessed ceiling luminaires, i.e. the entirespectrum of downlights, from recesseddownlights to washlights, recessed direc-tional spotlights and specific louvred luminaires, are specifically designed as in-tegral lighting elements. Floor and ceiling washlights in particular can be integrated into walls.

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Main housing of thespotlight

Adapter with a circuitselector switch forthree-circuit track

Facetted reflector forspot or flood versions

Exchangeable lighthead

Spotlight for low-voltage halogen lampswith integral transfor-mer. Housing andremovable light headform a modular systemthat allows a widerange of lighting options

Capsule low-voltagehalogen lamp with pinbase

Power supply andlocking of light headonto main housing

Anti-dazzle cylindermade of blackenedhigh-grade steel

Integral, conventionaltransformer

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Custom designed lumi-naire for the board-room in the Hongkongand Shanghai Bank.The elliptical luminaire(9.1 x 3.6 m) corre-sponds to the form ofthe conference table.The inner ring of theluminaire contains aseries of directionalspotlights, which arealigned to the seating.The outer ring containsa prismatic diffuser,which provides ambientlighting and some spe-cular effects.

Custom designed lumi-naire based on a stan-dard product: the opti-cal system of aconventional louvredluminaire (below) isused as the direct ele-ment within a linear secondary reflector lu-minaire (above).

Custom designed lumi-naire for the cofferceiling in the new en-trance to the Louvre.Fluorescent lamps (1)illuminate the sides ofthe coffers and provide indirect lighting as an integral ceiling ele-ment. An additionalspotlight (2) canbe used for accentlighting.

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3.3 Practical planning3.3.2 Luminaire selection

In the case of additive lighting the lumi-naires are not integrated into the archi-tecture, but appear as elements in their ownright. Besides planning the lightingeffects which are to be produced by theseluminaires, the lighting designer has tospecify the luminaire design and plan thelighting layout in accordance with the architectural design. The range of planningpossibilities extends from harmonizingluminaires with available structural systemsto selecting luminaires that will have anactive influence on the overall visual ap-pearance of the space.

Luminaires typically used for additivelighting are light structures, spotlightsand surface-mounted downlights. Due tothe fact that they are a separate elementfrom the ceiling, light structures offerwide scope for a variety of applications:they allow both direct and indirect orcombined direct-indirect lighting. Spot-lights, which can be mounted directlyonto the ceiling or onto suspended trun-king systems, are especially suitable when flexible lighting is required, e.g. fordisplay and exhibition purposes. What isgained in flexibility is offset by the task ofharmonizing the visual appearance of thelighting installation with the environmentand avoiding visual unrest through themixing of different luminaire types or by aconfusing arrangement of light structures.

There are numerous intermediate options between the extreme forms ofcompletely integral lighting and totallyadditive lighting. Integral lighting usingdownlights comes close to an additivelighting concept if semi-recessed, surface-mounted or pendant downlights areinstalled. The lighting requirements met byspotlights in an additive lighting conceptcan also be met by using recessed direc-tional spotlights. Lighting design and theluminaire selection are therefore not bound by the decision to opt for a distinctlyintegral or additive lighting solution.Within the available options a decision canbe made on a concept that correspondsto the architectural, aesthetic and lightingrequirements.

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Integral and additivelighting: identicallighting effects pro-duced by recessed downlights and down-lights mounted on alight structure.

Custom designed lumi-naires based on stan-dard products: a pris-matic panel mountedat a specific distancebelow the ceiling aper-ture of a standard downlight controls luminance distribution.The ceiling is illumina-ted and the shieldingof the lamp is improved.

The darklight reflectorin a conventional downlight is used asthe direct element in a rotationally sym-metrical secondaryreflector luminaire.

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3.3 Practical planning3.3.2 Luminaire selection

sufficient to provide ambient light – general lighting can therefore be producedby accent lighting. This shows that there are no longer any grounds for dividinggeneral lighting and accent lighting into distinctly different forms of lighting.Both areas overlap, in fact, the two are no longer separate, the one can now becombined with the other.

Luminaires with wide-angle distributionare most suitable for general lighting, especially louvred luminaires and lightstructures designed for fluorescent lamps,as found in a majority of installationsdesigned for work-places. Uniform lightingcan be equally well effected using indi-rect lighting provided by ceiling washlights,wallwashers or secondary luminaires.Above all, for the lighting of prestigiousspaces, such as lobbies or large meetingrooms, a close arrangement of narrow-beam downlights recessed in the ceiling isappropriate.

The choice of luminaires for accentlighting is less extensive and limited toluminaires that are able to produce con-centrated, directed beams of light. Down-lights are generally used for the staticlighting of horizontal lighting tasks, themore variable version being recessed directional spotlights. Movable spotlightson track or light structures offer the maximum flexibility in beam direction andvariability.

3.3.2.3 Stationary or movable lighting

The decision to opt for a stationary orvariable lighting installation overlaps thedecision to go for an integral or additivesolution; it is determined by the lightingrequirements the installation has tomeet rather than by design criteria.

There are different ways of making alighting installation flexible. Time-relatedor spatial changes can be produced in allpermanently fitted systems, whether theyconsist of recessed luminaires, surface-mounted luminaires or suspended struc-tures, by using a lighting control system.Individual luminaires or groups of lumi-naires can be dimmed or switched to ad-just the lighting to suit the changing usesof the space. The next step towards in-creased flexibility is the application ofpermanently fitted luminaires that can bedirected, such as directional spotlights orspotlights installed on singlets. The hig-hest degree of flexibility, as required forthe lighting of temporary exhibitions anddisplay lighting, is provided by movablespotlights mounted on track or trunkingsystems. This means that the lighting canbe adjusted using a lighting controlsystem, completely rearranged, realignedor individual luminaires substituted. Inthe decision to go for a more static or avariable lightig system there is a seamlesstransition between the extremes, whichallows the lighting to be adjusted to suitthe specific requirements.

3.3.2.4 General lighting and differentiatedlighting

The decision to design predominantly uni-form general lighting or more distinctlydifferentiated accent lighting depends onthe lighting task – it only makes sense to emphasize individual areas using light ifthere is a noteworthy difference in theinformation content between significantareas or objects and their surroundings. If the distribution of lighting tasks andinformation content is uniform across anarea, correspondingly general lighting will be appropriate.

Whereas uniform general lightingusually means a standard lighting designconcept, which is generally the case for the lighting of workplaces, a lighting designconcept that aims to create isolatedaccents may be regarded as an exception.As a rule, accent lighting will alwayscontain a general lighting component to allow the viewer to perceive the spatialarrangement of illuminated objects andprovide for orientation within the space.This general lighting can be produced bycertain luminaires, the ambient light theyproduce providing a background againstwhich significant areas can be picked outusing accent lighting to produce “focalglow”. Scattered light from the areas illu-minated by accent lighting is frequently

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Stationary and movableluminaires: identicallighting produced by directional spotlights and track-mounted spotlights.

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3.3.2.5 Direct or indirect lighting

The decision whether to plan direct orindirect lighting affects the proportion ofdirected or diffuse lighting in the spacesignificantly. This decision results in alighting concept which, in the case of in-direct lighting, is designed to producediffuse general lighting, whereas a directlighting concept may comprise both direct and diffuse light and both generaland accent lighting.

Indirect lighting provides the advantagethat it produces very uniform, soft lightand creates an open appearance due tothe bright room surfaces. Problems arisingfrom direct and reflected glare do not occur, making indirect lighting an ideal solution for critical visual tasks, such as work at VDTs.

It should be noted, however, thatindirect lighting alone produces very poormodelling and spatial differentiation.In addition, there is no accentuation of thearchitecture or the illuminated objects.The result may be a flat and monotonous environment.

Indirect lighting is achieved by thelight from a primary light source beingreflected by a substantially greater, mostlydiffuse reflecting surface, which inturn adopts the character of a large-scalesecondary reflector luminaire. The re-flecting surface may be the architectureitself: the light may be directed onto the ceiling, the walls or even onto the floor,from where it is reflected into the room.There is an increase in the number of so-called secondary reflector luminaireswhich are being developed. They consist ofa primary light source with its ownreflector system and a larger secondaryreflector. This design allows improvedoptical control of the emitted light.

Direct lighting, mostly using louvred luminaires, can also be used to producegeneral lighting with a predominant diffuse component. It may well also havea component of directed light. This givesrise to distinctly different lighting qualities,above all considerably enhanced mo-delling and more clearly defined surfacestructures.

A lighting design concept based ondirect lighting means that individual areaswithin the space can be purposefully lit from almost any location. This allows agreater degree of freedom when designingthe luminaire layout.

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Direct and indirectlighting: direct lightingusing downlights(above), indirectlighting using wall-mounted ceiling wash-lights (below).

General lighting anddifferentitated ighting:general lighting pro-vided by a regulararrangement of louvredluminaires and down-lights. Both compo-nents can be switchedand dimmed separatelyto produce a timeddifferentiation (above).Spatial differentiationis achieved by thearrangement of wall-washers and the grou-ping of downlights(below).

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by using downlights, especially thosedesigned for incandescent lamps, directedlight can be produced that accentuatesthe qualities of materials more intenselyand produces greater differentiationin the lighting of a space; this can be usedeffectively for the illumination ofprestigious spaces and for display lighting.A combination of both luminaire types is possible to create spatially differentiatedlighting or to increase the portion ofdirected light in general.

The illumination of horizontal surfacescan also be provided using indirect light.In this case the walls, or preferably theceiling, are illuminated to produce uniform,diffuse ambient lighting using thesesurfaces to reflect the light. Indirect lightconsists of vertical components to pro-vide a bright atmosphere in the space andhorizontal components for the actuallighting of the working area or floor. This canbe used for the lighting of corridors, forexample, to create a spacious impressionin spite of low illuminances. Indirectlighting is glare-free, which makes it es-pecially suitable for lighting visual tasksthat can be easily undermined by distur-bing reflected glare, e.g. at workstations. If more modelling is required to enhancethe three-dimensional quality of illumi-nated objects or to accentuate architecturalfeatures indirect lighting can be supple-mented by directed lighting, which providesthe required accentuation. In some casesvery little modelling is required, whichmeans that indirect lighting pro-vides anoptimum solution. It should be noted thatenergy consumption for an indirectlighting installation may be up to threetimes higher than that for a directlighting system due to restricted reflectionfactors.

In future, a combination of direct andindirect lighting will gain in significanceas opposed to exclusively direct orindirect lighting, in which case the indirectcomponent will provide general lightingwith a high degree of visual comfort, andthe direct component accent lighting for the working area and inherent visualtasks. Besides the combination of direct andindirect luminaires, either as individual luminaires or as integral luminaires inlight structures, secondary luminaires canalso be used. They emit both direct andindirect light and allow optical control ofboth.

3.3.2.6 Horizontal and vertical lighting

In contrast to the decision to opt for anintegral or additive lighting installation, orfor a static or variable concept, theextreme forms of exclusively horizontal orvertical lighting are hardly significantin practice: a portion of the missing form oflighting is almost always automaticallyproduced through the reflections on roomsurfaces and illuminated objects. In spite of this interdependence the cha-racter of a lighting installation is predo-minantly determined by the emphasis laidon either horizontal or vertical lighting.

The primary decision to provide horizontallighting is frequently in line with thedecision to plan functional, user-orientedlight. This is especially true in the case of lighting for workplaces, where the ligh-ting is predominantly designed as uni-form lighting for horizontal visual tasks.In such cases vertical lighting com-ponents are predominantly produced bythe diffuse light that is reflected by thehorizontal illuminated surfaces.

The decision to plan vertical lightingmay also be related to the task to fulfilfunctional requirements, especially in thecase of the lighting of vertical visualtasks, e.g. the reading of wall charts or theviewing of paintings. however, verticallighting frequently aims to present andcreate a visual environment; in contrastto horizontal, purely functional lighting,vertical lighting is intended to emphasisethe characteristic features and dominantelements in the visual environment. Thisapplies first and foremost to architecture,whose structures can be clearly portrayedby purposefully illuminating the walls, aswell as to the accentuation and modellingof objects in the space. Vertical lighting is also essential in order to facilitate com-munication, to ensure people’s facialexpressions are not concealed by the heavyshadows produced by single-componenthorizontal lighting.

3.3.2.7 Lighting working areas and floors

One of the most common lighting tasks is the illumination of horizontal surfaces.This category includes the majority oflighting tasks regulated by standards forworkplaces and circulation areas. This may be the lighting of the working plane(0.85 m above the floor) or the lighting of the floor itself (reference plane 0.2 mabove the floor).

The illumination of these planes can be effected by direct light, and a largenumber of luminaires are available forthis task. A variety of lighting effects canbe achieved depending on the choice of luminaires. Louvred luminaires or lightstructures for fluorescent lamps produceuniform general lighting, which is prima-rily required for workplaces. Conversely,

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Horizontal and verticallighting: the sameluminaire layout can beused for downlightsfor horizontal lightingas well as for wall-washers for verticallighting.

Horizontal generallighting from differentceiling heights: as arule, narrow-beamluminaires are used forhigh ceilings and wide-beam luminaires forlow ceilings to ensurethat the light beamsoverlap.

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3.3.2.8 Wall lighting

Wall lighting can fulfil a variety of tasks. It can be directed at vertical visual tasks onthe walls, e. g. textual information oncharts or posters, objects such as paintings,or retail goods, architectural structures or the wall surface itself. Wall lighting mayalso be intended to present the wall in its function as a room surface; finally, walllighting can be a means for providingindirect general lighting in a space.

To accentuate certain areas of wall orobjects on the wall spotlights and recesseddirectional spotlights are particularly suitable, depending on the degree of flexi-bility required. In the case of reflectingsurfaces, e.g. oil paintings or pictures fra-med behind glass, attention must be paid to the angle of incidence of the lightto avoid disturbing reflections that mayarise in the observer’s field of vision, if theangle is too low, or heavy shadowsthat may occur, e.g. shadows of the pictureframes on the pictures, if the angle ofincidence is too steep.

Grazing light provided by downlightsis especially suitable for accentuatingsurface structures. This type of lighting canalso be used exclusively for illuminatingwalls, if a scallop effect is required. Incorridors and exterior spaces in particulargrazing light on walls can be effectedusing uplights or combined uplight anddownlights. In any case the distribution ofthe scallops over the wall should be inline with the proportions of the space andfollow a regular rhythm. Asymmetricalspacing, which may be required dueto special features of the particular wallsurface, e.g. the positions of doors orobjects, is also possible.

If the wall is not to be revealed as aroom surface as such, but an open im-pression of a wall is required, then uniform,transitionless lighting should be used.Washlights are the most appropriate lumi-naires in this case. There are variousmodels available, including fixtures for linear walls, for walls with recesses andcorners, and for parallel walls in narrowspaces such as corridors. Washlights have aspecial reflector segment that producesdistinctly more uniform illumination of the wall than downlights in their basicform.

Totally uniform wall lighting is ob-tained using wallwashers, which, likewashlights, are available for recessed orsurface mounting or for mounting ontrack or trunking systems. Lighting wallsusing wallwashers or washlights alsoprovides uniform lighting of vertical visualtasks as well as indirect general lighting.

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General lighting(above), direct-indirectlighting of the work-place with directlighting in the circula-tion areas (below).

Direct light on theworking area togetherwith wall lighting(above), secondary re-flector luminairesprovide light on theworking plane (centre),indirect generallighting and lightingfor the workplace usingthe ceiling as a reflec-tor (below).

Indirect generallighting (above), direct-indirect lighting of the workplace with di-rect lighting in thecirculation areas(centre), directed lighton the working planewith indirect lightingin the circulation areas (below).

Illumination of work-ing areas in an office:different lightingconcepts can be applied,depending on the type of room and howit is used.

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The greater the cut-offangle, the greater thevisual comfort provi-ded by the luminairedue to improved glarecontrol. The samelighting layout willproduce different distributions on thewalls. As the cut-offangle increases, so the beam spread willdecrease, as is the casefor the combinationsshown for the 30°, 40°and 50° angles illustra-ted.

Wall lighting using ro-tationally symmetricalluminaires (from leftto right): lens wall-washer, directionalwashlight, washlights,wallwasher, track-mounted wallwasher.

Wall lighting using linear luminaires (fromleft to right): wall-washer for fluorescentlamps, wallwasher withprismatic element,wallwasher with lou-vred reflector, adjust-able wallwasher, track-mounted wallwasher.

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3.3.2.9 Ceiling lighting

Ceiling lighting can be the sole purpose oflighting this room surface, especiallywhen the ceiling has an informative valueof its own due to paintings or architec-tural structures. Ceiling lighting is generallyused as a means for providing indirectgeneral lighting of a space. This means thatthe ceiling becomes the brightest roomsurface and as such does not correspond tothe relative information content. Whenusers spend longer periods of time in thespace the ceiling luminance – like anovercast sky – can therefore be felt to bedisturbing or is ultimately a source ofglare; this applies to luminous ceilings inparticular, where it is not the ceiling that is illuminated, but where the ceilingitself becomes an extensive luminaire.

Ceiling lighting can be created usingceiling washlights for mounting on orinto the wall; a particularly relevant formof ceiling lighting is cove lighting. If it is not possible to install luminaires on thewalls, as is often the case in historicalbuildings, then free-standing ceiling wash-lights can be installed. Ceilings can also be illuminated using pendant luminaires orlight structures that light the upper half of the space. This option is only applicableif there is sufficient room height, as allluminaires must be mounted above headheight to avoid direct glare and they mustbe installed at a suitable distance fromthe ceiling to ensure uniform light distri-bution. If certain areas of the ceilingare to be accentuated, this can be achievedusing uplights; this method is also suitable for rooms with low ceilings.

3.3.2.10 Luminance limitation

The question of how to control glare variesdepending on whether the luminaires are stationary or movable. In the case ofdirectional luminaires, such as recesseddirectional spotlights, glare does dependon the light distribution of the luminaire.The glare primarily occurs if the luminaireis not adjusted correctly and the lightsource becomes visible, either in the lumi-naire itself or through a reflection of the lamp from specular room surfaces.

In the case of stationary luminaires,such as downlights, louvred luminaires orlight structures it is necessary to distin-guish between the elimination of directglare and reflected glare. In the case ofdirect glare the quality of glare limitationdepends on the light distribution of theluminaire. Standards exist for the lightingof workplaces, which stipulate minimumcut-off angles or highest permissible lumi-nances in the cut-off range. For work-stations with VDTs there are specificrequirements.

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Wall lighting using washlights (above) andwallwashers (below).

Application of narrow-beam downlights forgrazing wall lightingwith decorative scallops.

Ceiling lighting usingwall-mounted ceilingwashlights, pendantindirect luminaires anda wall-mounted direct-indirect luminaire(from left to right).

Free-standing lumi-naire providing asym-metrical indirectlighting, free-standingluminaire providingsymmetrical indirectlighting, free-standingluminaire providingasymmetrical direct-indirect lighting (fromleft to right).

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To ensure that lumi-naires are electricallysafe they are requiredto meet specific safetystandards. These stan-dards require all metalparts which users cantouch not to be live ifa fault occurs. The pro-tection class indicatesthe measures of safetyprovided.

Luminaires are protec-ted against the ingressof foreign bodies andwater. The Mode ofProtection (IP) is an in-ternationally recogni-sed system comprisingtwo digits XY, whereby

X refers to protectionagainst foreign bodiesand Y protectionagainst water. The minimum requirementslaid down for lumi-naires in interior spaces is IP 20.

Conventional IP XYclassification for lumi-naires.

Symbols used to indi-cate special qualitiesand safety require-ments.

Protect. class Protection measures

I The luminaire has a connection point for an earthed conductor, to which all metal partswith which users may come into contact must be connected. Connection to the mains earthconductor is imperative.

II The luminaire is insulated such that there are no metal parts which users can touch that maybe live if a fault occurs.

There is no earth conductor.III The luminaire is operated on low-voltage up to

42 V, supplied via safety tranformers or batteries.

Luminaire with discharge lamp, suitable for mounting on parts of buildings com-prising materials with an ignition point of >200°C (e.g: wooden ceilings)

Luminaire with discharge lamp with a limited surface temperature, suitablefor installation in areas exposed to dustor containing inflammable materials orin danger of explosion

Luminaire suitable for installation in or surface mounting on furniture made of standard inflammable material (coated, veneered or paintedwood)

T

TT

M

X Degree of protection against foreign bodies Y Degree of protection against water

0 No protection1 Drip-proof: water/spray from above

2 Protection against foreign bodies > 12 mm 2 Drip-proof: water from an angle(protection against manual contact) (up to 15° to the vertical )

3 Protection against foreign bodies > 2.5 mm 3 Protected against spray(up to 15° to the vertical)

4 Protection against foreign bodies > 1.0 mm 4 Protected against spray from alldirections

5 Protection against dust 5 Protected against jets of water from alldirections

6 Dust-proof 6 Water-proof: flooding7 Water-proof: immersible8 Water-proof: may be submerged

Luminaire suitable for installation in orsurface mounting on furniture with unknown inflammable properties

Safety distance (X) in the direction ofbeam

X6 • • •5 • • • •4 • • •32 • • •

0 1 2 3 4 5 6 7 8 Y

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Air-conditioning similarly gives rise to a number of questions; requirements laiddown by the lighting and the aircondi-tioning have to be coordinated to ensurethat the ceiling design is harmoniousand no conflicts arise in the organisationof ducting. Air-handling luminaires resultin a considerable reduction of ceilingapertures and contribute towards creatinga uniform ceiling layout. Depending ontheir design these luminaires can handleair supply, air return, or both air supplyand return. If more luminaires are requiredthan for air-conditioning purposes, air-handling dummies can be used that areidentical in appearance to the air-handlingluminaires, but are not connected to theventilation system. Air-handling versionsof both louvred luminaires and down-lights are available.

3.3.2.13 Accessories

A wide variety of luminaires can beequipped with accessories to change theirlighting or mechanical properties. Theseinclude filters to change the luminouscolour or to reduce the UV or infraredradiation, spread lenses to change distribu-tion characteristics, anti-dazzle equip-ment or mechanical shields, e.g. for pro-tection relating to ball games. For furtherdetails, refer to section 2.6.5.

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In the case of luminaires with mirror re-flectors direct glare control improves thegreater the cut-off angle, i. e. narrowbeam spreads. The standard cut-off anglesare 30° and 40°. It is not possible to limitreflected glare by increasing the cut-offangle, however. Correct positioning of the luminaires is essential in order to avoidreflected glare. Any luminaire installed in the critical area of the ceiling over aworkplace is a potential source of reflectedglare. The critical area can be defined as that portion of the ceiling which is seenby the user in a mirror covering theworking area.

3.3.2.11 Safety requirements

Luminaires are required to meet the safetyrequirements in all cases; in Germany this is usually guaranteed through the pro-vision of a VDE seal of approval. In somecases there are other requirements thathave to be met and the luminaires mar-ked accordingly. This applies primarily tofire safety when luminaires are installedin or on furniture or other inflammable ma-terials. Special requirements also have to be fulfilled by luminaires that are to beoperated in damp or dusty atmospheres,or in rooms where there is a danger of ex-plosion.

Luminaires are classified according to their Mode of Protection and ProtectionClass, whereby the protection class in-dicates the type of protection providedagainst electric shock, and the Mode ofProtection its degree of protection againstcontact, dust and moisture. Luminaires for application in environments exposed todanger of explosion must meet a furtherset of requirements.To ensure safety against fire, luminairesdesigned for discharge lamps, which areto be mounted on inflammable or easilyinflammable materials, must meet the cri-teria to be marked with the T symbol.

Luminaires to be mounted on furniturerequire the M seal of approval if they are to be installed on or in inflammablematerials. If the flammability of thematerials is not known, the MM symbol isrequired.

3.3.2.12 Relation to acoustics and airconditioning

The acoustics are of primary importancein concert halls, theatres, auditoriums andmultipurpose spaces. Acoustical criteriaare therefore treated with priority when theceiling is designed; this may have an in-fluence on the choice and arrangement ofthe luminaires. Recessed downlights have been proven to be the most suitablefor this kind of lighting task, as they have the smallest surface area which maybe acoustically significant.

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3.3.2.14 Lighting control and theatricaleffects

Theatrical effects are increasingly beingapplied in the field of architectural lighting.These include dramatic contrasts, theuse of coloured light and projections usingmasks and gobos.

Some of these effects can be obtainedusing conventional luminaires, throughstriking qualities such as coloured light, orby dramatic modelling, by using accentlighting to divide up the space or by usingsuitable lighting control. Some luminairescan be equipped with filters and lens systems that allow distribution characte-ristics to be changed and projections of effects using masks and gobos which areparticularly suitable for such lightingtasks.

If a high degree of flexibility is requiredalong with the possibility to controllighting effects with respect to time andlocation, then special luminaires arerequired that allow colour changing andthe variability in light distribution, orpossibly even direction control by remotecontrol. Such luminaires, which havebeen used primarily for show lighting todate, are now being developed forinterior and exterior architectural lighting.

3.3.3 Lighting layout

Depending on the specific lighting project,there may be a number of conditions that determine the lighting layout. Thefirst is related to the particular lightingtasks. Differentiated lighting for differentparts of the room or functional areasmay result in the luminaires having to bearranged accordingly, e.g. the arrange-ment of downlights above a seating areaor the positioning of downlights andfloodlights in a modern control room.Uniform lighting will require the luminairesto be arranged regularly across the area.

The lighting layout may also dependon the form of the ceiling; existing ceilinggrids and modules, but also ceiling joistsor other ceiling shapes form structures thathave to be taken into account whenplanning the lighting layout. In some casesit is also necessary to coordinate plan-ning with the engineers responsible for air-conditioning and acoustics to ensure that the cabling installation is carried outsafely and that the ceiling appearance is acceptable.

The lighting layout should not be basedentirely on technical or functional condi-tions; in spite of all the preconditionsthere is wide scope for arranging the lumi-naires in accordance with the designconcept. The lighting should not be confi-ned by purely technical considerations, but also take into account the aestheticsof ceiling design. In quantitative lightingdesign it has become common practice to

3.3 Practical planning3.3.3 Lighting layouts

plan the lighting layout of ceiling-mountedluminaires to produce a completely uni-form grid, with the aim of providing uni-formly distributed lighting. By super-imposing light distribution patterns it ispossible to produce uniform lighting also by means of a differentiated lightinglayout. On the other hand, differentiatedlighting can also be achieved with a uni-form arrangement of various luminaires.Consequently, there is no direct link betweenlighting layout and lighting effect; byexploiting the wide range of luminairesavailable it is possible to achieve a de-signed pattern of lighting effects using avariety of lighting layouts. The lightingdesign should make use of this scopeproducing ceiling designs that combinefunctional lighting with an aestheticlighting layout that relates to the archi-tecture.

It is neither possible nor practical topresent a comprehensive formal languagefor the design of lighting layouts; the ceiling design of a lighting installation isdeveloped in each specific case from the correlation of lighting tasks, technicalprerequisites, architectural structuresand design ideas. It is, however, possibleto describe a series of basic conceptswhich show some general approaches to theform and design of luminaire patterns on ceiling sufaces.

One approach is to consider the point as a basic design element. In the broadestsense the point can be any individualluminaire, or even any compact and spati-ally isolated group of luminaires. This category of design elements not only in-cludes downlights, but also larger lumi-naires such as louvred luminaires and evengroups of these individual elements, pro-vided that their total surface area is smallin relation to the overall surface of theceiling.

The simplest layout of these points is a regular grid, in a parallel or staggered ar-rangement. A regular pattern of identicalluminaires can easily result in a monoto-nous ceiling appearance, plus the factthat differentiated lighting is practicallyout of the question. An alternating gridof different individual luminaires or lumi-naire combinations can produce moreinteresting arrangements; in this case lumi-naires of the same or different types canthen be purposefully combined. The useof different luminaire types, by alternatingpositioning or through combinations, allows the lighting qualities of a visualenvironment to be carefully controlled. A further step towards more complex de-sign forms is the linear arrangement ofpoint sources. In contrast to simple ligh-ting layouts in grid patterns, the ceilingdesign in this case relates more closely tothe architecture of the space – the ceiling is no longer simply covered witha grid of luminaires, but is designed along the lines dictated by the architectural

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Linear arrangement ofceiling luminaires follows the length ofthe long walls. The endwall is illuminated separately, by a linear arrangement of reces-sed floor luminaires.

Point sources: regularand staggered layouts.

The point sources maybe luminaires of diffe-rent shapes and sizes,or compact groups of luminaires.

Point sources: linear arrangements.

Luminaire arrangmentscan follow architectu-ral structures or createpatterns of their own.

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A regular arrangementof ceiling luminairesprovides the ambientlighting in the space.The long walls are accentuated separatelyby recessed floor lumi-naires.

Linear and point ele-ments: regular andstaggered arrange-ments.

The combination ofdifferent elements gives rise to a broadrange of design possi-bilities, includingdecorative solutions.

Linear elements: regular and staggeredarrangements.

The rectangular arrangement of track isin line with the form of the space. This allowsflexible lighting of all wall surfaces andaccentuating of objectsin the space.

Linear structures: linear and rectangular arrangements of track.

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tween the wallwashers should not exceedone and a half times the distance to thewall.

When illuminating paintings or sculp-tures using spotlights, the luminairesshould be arranged so that the angle ofincidence of the light is approximately30°, the so-called “museum angle”; thisproduces maximum vertical lighting and avoids reflected glare that may disturbthe observer.

form of the space. This may involve follo-wing the existing lines or purposefullyarranging the luminaires in contrast to theexisting formal language. Linear ar-rangements allow greater design scope,but do entail more stringent designrequirements. As the linear arrangementof the luminaires does not necessarilyrelate to an actual line – the course a wallfollows, ceiling projections or joists – theluminaire arrangement can only be createdon the basis of the perception of gestalt.These laws of gestalt must receive specialattention during the planning phase. The crucial criteria are the proximity of theluminaires and their equidistance.

Whereas linear arrangements consistingof series of points are only produced indi-rectly by the perception of the gestalt,they can be directly formed of linear ele-ments. These linear elements can be parti-cular types of luminaires, e.g. louvred luminaires, or even trunking systems. Con-tinuous systems, light structures andalmost all track arrangements or othertrunking systems belong in this designcategory.

The formal language of linear arrange-ments is identical to that of rows ofpoints. As the visual forms produced whenlinear luminaires are used are real and not only implied, more complex arrange-ments can be planned with no danger of distortion through perception. Creative

design allows both the alternating appli-cation of different luminaire forms andthe use of spotlights on lighting structuresor trunking systems. This allows differen-tiated lighting without individual lumi-naires disturbing the in-trinsic form of thestructure.

The application of linear elements also allows the transition from linear arrange-ments to more planar layouts. Lightstructures and trunking systems are parti-cularly suitable in this regard. The formallanguage of such networking dependsprimarily on the connectors available forthe specific structures. Adjustableconnectors allow specially variable design.In general, connectors are available withfixed angles of 90° and 45°, 120° and 60°.Each of these angles can produce a widerange of forms, from rectangular forms atangles of 90° to honeycomb-shaped arrangements at angles of 120°.

Apart from basic design concepts it is possible to compile a set of general rulesfor some aspects of lighting layouts; in the case of regular lighting layouts thisapplies above all for the distances be-tween the luminaires and from the walls.

For ceiling-mounted downlights thedistance to the wall should be about halfthe distance between the downlights. In the case of wallwashers the recommen-ded distance to the wall is around onethird of the room height, the distance be-

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An arrangement of several hexagonal lightstructures subdividesthe ceiling area irre-spective of the sur-rounding architectureand becomes an activedesign element in thespace.

Light structures using90°, 135° and 120°angles in arrange-ments: individual andcombined structures.

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The recommendeddistance of downlightsto the wall is generallyhalf the distance be-tween the downlights.Corner-mountedluminaires should bemounted on the 45°line to produce identi-cal scallops on bothwalls.

The distance of wall-washers and wash-lights from the wallshould be 1/3 of theroom height; the dis-tance between the lu-minaires themselvesshould not exceed oneand a half times the distance to the wall.

In spaces with domi-nant architectural fea-tures the lighting lay-out should harmonizewith the architecturalelements.

In the case of mirrorwalls the lighting lay-out should be plannedsuch that the arrange-ment of luminairesappears consistent inthe mirror image.

The optimum angle ofincidence for the illu-mination of paintingsand sculptures is 30°.

Overlapping light beams (beam spreads60°, 80° and 100°) onthe working plane at a spacing to height toheight ratio of 1:1.

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Critical areas (excluded zones) forVDT workstations ( left),horizontal visual tasks(centre) and verticalvisual tasks (right). Luminances falling onthe visual tasks fromthe zones indicated re-sult in reflected glare.

Lighting solutions forhorizontal visual tasksfree of reflected glare:direct lighting usingluminaires positionedoutside the excludedzone, indirect lighting.

Lighting solutions forvertical visual tasksfree of reflected glare:(from left to right): if the reflective surfaceis arranged transver-sely, the luminaires canbe mounted in front of the excluded ceilingzone. If the reflectivesurface is arrangedvertically, then next to

the excluded ceilingzone (centre). If theentire wall surface isreflective, the lumi-naires must be moun-ted within the exclu-ded zone; the cut-offangles must be plan-ned such that the ob-server is not disturbedby reflected light.

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3.3.4 Switching and lighting control

In the simplest case a lighting installationmay consist of a single circuit. An instal-lation of this kind can only be switched onand off and therefore only produces onelighting arrangement. Lighting frequentlyhas to meet changing requirements,however, which means that additional con-trol options must be provided.

Even if the space is always used in thesame way, daylight conditions change radi-cally during the course of the day. In thedaytime artificial lighting must competewith sunlight, and our perception is adap-ted to high levels of brightness on theroom surfaces. In the evening and at nightlower illuminances and pools of light areaccepted. This fact presents a significantplanning criterion for a wide range oflighting tasks. In some cases, e.g. thelighting of exclusive restaurants, it is likelyto be a prime consideration and require a lighting installation to meet both envi-ronmental situations.

As the use of the space changes, so thedemand for variability and flexibility willincrease. For example, the lighting providedin lecture rooms should consist of accentlighting for podium discussions with com-paratively high levels of lighting in theauditorium; the lighting installation shouldalso be suitable for slide presentations,where the speaker is seen in accentlighting and the ambient light is just suf-ficient for the people in the audience totake notes. If films or videos are to beshown, lighting control requirements willbe extended accordingly.

In many cases, the creation of a differen-tiated lighting installation cannot be re-stricted to the development of a conceptthat meets a clearly defined set of require-ments with an equally fixed, exclusivelyspatially differentiated lighting layout.Changing environmental conditions anddifferent uses may demand the creation oftemporal differentiation – that is to say,the transitions from a fixed lighting situationto a series of optional light scenes thatare dependent on the time of day or givensituations.

The first way of creating a light sceneis to arrange individual luminaires in an installation to form groups that can beswitched separately. These groups mayconsist of lighting arrangements that arecompletely independent of one anotherand designed to fulfil different lightingtasks, and individual components of anoverall installation, which may be operatedseparately or together.

As a rule, the definition of a lightscene does not simply cover the simpleswitching of groups of luminaires, butalso involves varying the levels of bright-ness. Besides the switching of separatecircuits, dimming equipment is requiredfor the separate groups of luminaires.

3.3 Practical planning3.3.4 Switching and lighting control

Once the required level of brightnesshas been identified, it is then possible toplan differentiated lighting to meet speci-fic requirements. The potential range oflight scenes increases considerably even ifthe number of luminaires and the swit-ching remains the same. The distributionand level of brightness of the lighting canbe accurately controlled in individualareas within the space and the overall levelof a light scene adjusted to the changingrequirements–e.g. to the time of day or thedaylight available.

The switching and dimming of individualgroups of luminaires can be controlledmanually, either using conventional swit-ches and controllers or by infrared remotecontrol, which allows groups of lumi-naires to be controlled even if there areonly a minimal number of circuits.

This method still makes it difficult toreproduce defined light scenes or toadjust them at a fixed rate. If the require-ments the lighting control has to meet are complex, or if a larger number of groupsof luminaires are to be controlled, it is advisable to use an electronic controlsystem. This allows precisely defined lightscenes to be recalled at the touch of abutton, or a change of light scene to beprogrammed to take place over a givenperiod of time. It is also possible to con-trol the light in accordance with daylightor the use of the spaces using sensors;other functions apart from lighting canalso be operated by coupling the lightingcontrol system with the building manage-ment system.

Further developments in lightingcontrol can also be used to create theatricaleffects in architectural lighting. Besidescontrolling brightness, this may includechanging luminous colour, beam spreador even the direction of the luminaires.

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3.3 Practical planning3.3.4 Switching and lighting control

151

Diagram of the lightinglayout in a multifunc-tional space with theluminaires allocated todifferent circuits. Circuits: 1 wall lighting;2, 3 general lighting; 4 decorative compo-nents; 5–10 track.

Conference: high level of horizontalgeneral lighting,average level on walls.

Lecture: reduced generallighting, emphasis ofwall surfaces, accentlight on speaker.

Scene 1 Reduced night-timelighting Scene 2 Morning lighting Scene 3 Daylight-relatedlighting to supplementdaylight

Time-related lightscenes in a hotel foyer.Transition betweenlight scenes withfading times of up to15 mins.

Scene 4 Warm early eveninglightingScene 5 Festive lighting for theevening Scene 6 Reduced festivelighting

Slide presention: general lighting redu-ced for people to take notes by, minimumwall lighting, accentlight on speaker.

Film or video projec-tions: minimum general lighting.

Dining: low wall lighting,festive atmosphereproduced by decorativecomponents 4,accentuation of pointsof interest on tablesand buffet using track-mounted spotlights.

Reception: room proportions areemphasised by the walllighting, festive atmos-phere due to decora-tive components 4,accentuation of pointsof interest in the spaceusing track-mountedspotlights.

Switching and dim-ming status of circuits1–10 for different light scenes:

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a

b

3.3 Practical planning3.3.5 Installation

3.3.5 Installation

A wide range of luminaire types – e.g.spotlights, combined uplights-downlightsand light structures – are exclusivelydesigned to be installed as additive ele-ments. They may be mounted on track or carrier systems, suspended from the ceiling (pendant luminaires) or surface mounted onto the wall or ceiling. The rangeof downlights and louvred luminairesavailable is so vast and their designs differsubstantially, which means that numerousmodes of installation are required. In thecase of wall or floormounting the lumi-naires may be surface-mounted or recessedinto the fabric of the building. Ceilingmounting allows a variety of possiblities:pendant mounting, surface mounting,semi-recessed or recessed mounting. Lightstructures can be handled in a similarway, i.e. depending on their design, theycan either be surface-mounted or recessed.

3.3.5.1 Ceiling mounting

Luminaires can be recessed into concreteceilings or suspended ceilings; the mode ofrecessing depends essentially on thespecific ceiling type.

For recessed mounting into concreteceilings the luminaire apertures are createdwhen the ceiling is cast. One method forproviding the apertures is to fix polystyreneblocks in the form of the required spaceonto the concrete shuttering; when theceiling has been cast the blocks are re-moved, providing apertures of the requiredsize. Another possibility is to install pre-fabricated housings, which are also attachedonto the concrete shuttering and remainin the ceiling. It is essential to check thatthe planned lighting layout is compatiblewith the structure of the ceiling, whetherspecific installation locations must beavoided, for example, due to concealedjoists or whether the reinforcement of theceiling should be coordinated with thelighting layout.

Shaped concrete ceilings, e.g. mouldedcoffer ceilings, can be used as effectivelighting elements. This may be to produceindirect lighting components and glare-freelighting, and will inevitably accentuatethe ceiling structure. The luminaires can beinstalled in the coffers to illluminate the sides of the coffers; the more conven-tional method is to install the luminairein the coffer as a pendant fitting, providingdirect lighting in the space and indirectlighting through the illumination of theceiling coffer.

152

Mounting recessedluminaires using aconcrete housing ( left),with a polystyreneblock and a substruc-tion (right).

the luminaire and building surfaces bthere must be at least25 mm. In the case of luminaires with anT mark no gap isrequired between theupper surface and the building surface.

Installation of recessedluminaires accordingto the European stan-dard (EN 60598): the minimum distancea between the sides of the luminaires andbuilding surfaces mustbe 50–75 mm. Betweenthe upper surface of

Methods of mounting recessed luminaires(from the top down-wards): mounting intoplaster ceilings using a plaster ring, mountinginto dry ceilings withluminaire attachment,mounting from abovewith mounting ring.

Semi-recessed moun-ting using a spacerring (above), or surface-mounted luminairesusing a mounting ring(below).

Mounting recessed luminaires in inclinedceilings: tiltabledouble-focus down-light (above), recesseddirectional spotlight(centre) and downlightwith special accesso-ries (below).

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3.3 Practical planning3.3.5 Installation

The recessed mounting of luminaires into suspended ceilings varies dependingon the type of ceiling system.

In the case of flat suspended ceilings,e.g. plasterboard ceilings, the luminairescan almost always be arranged irrespectiveof the suspended ceiling grid. The lumi-naires are fixed firmly in the ceiling aper-tures provided; if necessary, the weight ofthe luminaire must be carried by additionalsuspensions fixed onto or in close proxi-mity to the luminaire. If the ceiling is to beplastered, plaster rings are required forthe luminaire apertures.

There are various versions of suspendedceilings available made of individualpanels. They vary according to the material,grid dimensions and load-bearing capacity. The ceiling grid will automaticallydetermine the possible layout, which is to be taken into account when positioningthe luminaires.

Smaller luminaires, such as down-lights, can be installed in ceiling panels,following the same mounting instructionsas for flat ceilings. Larger luminaires, es-pecially louvred luminaires, can be installedin place of individual ceiling panels;different modes of installation are requiredfor mounting into different ceiling types.Metal plank ceilings present a special case:luminaires are not only installed betweenthe ceiling panels, but also from the carriersystem. Suspended ceilings made of in-dividual panels may require the luminairesto have additional brackets to take theweight of the luminaires.

For open grid ceilings and honey-comb-grid ceilings there are recessed cassettes available complete with suitableapertures for the recessed mounting ofdownlights. The cassettes are dimensionedto suit the respective ceiling grids. Theycan replace a ceiling panel or allow theinstallation of luminaires between ceilingpanels which would otherwise not besuitable to take the static load.

Semi-recessed mounting of luminaires issimilar to recessed mounting, with therecessed depth naturally being shallower.Some luminaire types are specificallydesigned for semi-recessed mounting. Withspecially developed recess accessories, luminaires for both recessed and surfacemounting can be adapted for semi-recessed mounting.

Pendant mounting can be effected in a variety of ways. Light-weight luminairesare usually suspended by the connectingcable. Heavier luminaires require a sepa-rate suspension device. This may take the form of a stranded wire cable or a pen-dant tube, which generally contains theconnecting cable.

153

Pendant mounting of louvred luminaires:with two suspensionpoints, four suspensionpoints, two and foursuspension cablesconnected to one ceiling mounting plate.

Recessed mounting oflouvred luminaires intovarious ceiling systems(from the top down-wards): recessed mountinginto ceilings withexposed and concealedprofiles, recessed mounting into flat,suspended ceilings andpanelled ceilings.

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3.3 Practical planning3.3.6 Calculations

3.3.5.2 Wall and floor mounting

Luminaires can be mounted onto wallsurfaces or recessed into the wall. The latter can be in either concrete or hollowwalls. Installation of floor-mounted lu-minaires can only be recessed. The luminairecover must be robust and provide pro-tection against the ingress of moisture.

3.3.5.3 Suspension systems

Suspension systems are generally designedfor pendant mounting from the ceiling, in the same way as for luminaires usingwire cables or pendant tubes. In somecases it is also possible to mount carriersystems onto walls by means of cantileverbrackets.

Track can be mounted in a variety ofways. It can be suspended from the ceiling or mounted directly onto walls orceiling. Recessed mounting into walls or ceiling is also possible in the case ofcertain versions or it can be used as part of a carrier system in a suspended ceiling.

Wide-span carrier systems are aspecial case. They can be suspended fromthe ceiling, spanned between two walls or erected as a free-standing structure.

3.3.6 Calculations

When planning a lighting installation it is necessary to perform a series of calcu-lations. In general, these refer to theaverage illuminance required or exact illu-minance levels in specific parts of thespace. It may also be of significance tocalculate the luminance of specific partsof the space, or different lighting qualities,such as shadow formation and contrastrendition, or the costs for a lighting instal-lation.

3.3.6.1 Utilisation factor method

The utilisation factor method is used toacquire a rough estimation of the dimen-sioning of a lighting installation; it allowsthe designer to determine the number of luminaires required to produce the de-fined illuminance on the working plane,or, vice versa, the illuminance on the working plane produced by a given num-ber of luminaires. This method does notprovide exact illuminances at specific pointsin the space, which means that othermethods must be applied to calculate theuniformity of a lighting installation or to determine illuminance levels at specificpoints. The utilisation factor methodis based on the fact that the average ho-rizontal illuminance for a space of a given size can be calculated from the over-all luminous flux produced by the lumi-naires installed, the light output ratio andthe utilance. In general terms, it describes

154

Mounting track (fromthe top downwards):surface-mounted, forrecessed mountinginto solid ceilings, sus-pended flanged trackwith ceiling panels.

Installation of recessedfloor-mounted lumi-naires: the housing isinserted into the floor.The luminaire itself is secured into the housing and is flushwith the floor surface.

Pendant mounting oftrack and structural systems (from left toright): pendant tubewith ceiling canopy forelectrical connection,wire suspension withceiling canopy for electrical connection,wire suspension with adjustable height.

Luminaires mountedon wall brackets (fromthe top downwards):cantilever bracket,bracket with integraltransformer, bracketfor partition walls.

Mounting of wall lumi-naires (from the topdownwards): recessedmounting into masonry,hollow walls, surface-mounting onto walls.

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3.3 Practical planning3.3.6 Calculations

the portion of luminous flux emitted bythe light sources, which falls on theworking plane after interaction with lumi-naires and room surfaces. The decidingfactor in this calculation is the utilance,which is derived from the geometry ofthe space, the reflectance of the room sur-faces and the efficiency and the distri-bution characteristics of the luminairesused.

To be able to calculate the appropriateutilance in each individual case, there are tables available, which contain theutilance of a standardised space withchanging room geometry, changing re-flection factors and luminaires with avariety of distribution characteristics. Thebasic, idealised space is presumed to beempty and of regular shape and propor-tions, i.e. rectangular and having the ratioof length to width approx. 1.6 to 1. The luminaires are presumed to be arrangedin a regular pattern on the ceiling, eithermounted directly onto the ceiling or sus-pended from the ceiling. These standar-dised values have a decisive influence onthe accuracy of the calculations for theapplication. If the conditions inherent inthe basic concept are in line with those inthe model space, the results will be rea-sonably accurate. The more the basic con-ditions deviate from the standardisedconditions, e.g. if the lighting layout is distinctly asymmetrical, it must be acceptedthat an increasing number of errors willoccur in the calculation.

When using the utilisation factor method an appropriate utilance table hasto be used for each type of luminaire. Thecorresponding standard luminaire classifi-cation table can be used for this purpose.Luminaire classification in accordancewith DIN 5040 and the German LightingEngineering Society is made up of oneletter and two digits, a combination indi-cates a number of luminaire qualities. The letter defines the luminaire class andindicates whether a luminaire emits light primarily in the upper or lower partof the space, i.e. direct or indirect ligh-ting. The first digit refers to the proportionof luminous flux falling onto the workingplane in the lower part of the space. Thesecond digit indicates the correspondingvalue for the upper part of the space. It isoften not necessary to use the standardtable of luminaire classification, as exacttables are supplied by the lighting manu-facturers.

155

Light output ratio hLB:ratio of the luminousflux emitted by a lumi-nair ÏLe under opera-ting conditions to theluminous flux of thelamp ÏLa.

Utilisation factor method: formula forcalculating the nominal illuminance EN for a given number of lumi-naires or the numberof luminaires n for a given illuminance.

Typical light output ratios hLB for direct luminaires with variouscut-off angles and lamp types.

Luminaire Lamp type hLB

Louvred luminaire 30° T26 0.65–0.75Louvred luminaire 40° T26 0.55–0.65Louvred lumin. square TC 0.50–0.70Downlight 30° TC 0.60–0.70Downlight 40° TC 0.50–0.60Downlight 30° A/QT 0.70–0.75Downlight 40° A/QT 0.60–0.70

EN (lx) Nominal illuminancen Number of luminairesa (m) Length of spaceb (m) Width of spaceÏ (m) Luminous flux per luminairehR UtilancehLB Light output ratioV Light loss factor

ÏLa

ÏLe

æLB = ÏLeÏLa

EN = V . n . Ï . æR . æLBa . b

n = . En . a . bÏ . æR . æLB

1V

SEAN MAC
SEAN MAC
SEAN MAC
SEAN MAC
SEAN MAC
SEAN MAC
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3.3 Practical planning3.3.6 Calculations

156

The room index k describes the influenceof the room geometryon the utilance. It iscalculated from thelength and width ofthe room, and theheight h above the

Utilance values hR fortypical interior lumi-naires (from the topdownwards): narrow-beam luminaires (A 60,DIN 5040)

working plane underdirect luminaires (roomindex k) and height h'above the workingplane under predomi-nantly indirect lumi-naires (room index k').

Light loss factor V inrelation to the degreeof deterioration in thespace.

Wide-beam luminaires (A 40, DIN 5040)

Indirect luminaires (E 12, DIN 5040)

The appropriate utilance is calculatedfrom the specific roomindex k (k ') and thecombination of the reflectance factors ofceiling (RC), walls (RW )and floor (RF).

V Degree of Deterioration

0.8 Normal deterioration0.7 Increased deterioration0.6 Heavy deterioration

hR RC 0.70 0.70 0.70 0.70 0.70 0.50 0.50 0.20 0.00RW 0.70 0.50 0.50 0.20 0.20 0.50 0.20 0.20 0.00RF 0.50 0.20 0.10 0.20 0.10 0.10 0.10 0.10 0.00

k0.60 1.04 0.86 0.84 0.81 0.80 0.84 0.80 0.80 0.781.00 1.17 0.95 0.92 0.90 0.88 0.91 0.88 0.87 0.851.25 1.26 1.06 0.98 0.98 0.95 0.97 0.95 0.94 0.921.50 1.30 1.04 1.00 1.00 0.97 0.99 0.97 0.96 0.942.00 1.35 1.07 1.02 1.04 1.00 1.01 0.99 0.98 0.972.50 1.38 1.09 1.03 1.06 1.02 1.02 1.01 0.99 0.973.00 1.41 1.11 1.05 1.08 1.03 1.03 1.02 1.00 0.994.00 1.43 1.11 1.05 1.09 1.03 1.03 1.02 1.00 0.98

hR RC 0.70 0.70 0.70 0.70 0.70 0.50 0.50 0.20 0.00RW 0.70 0.50 0.50 0.20 0.20 0.50 0.20 0.20 0.00RF 0.50 0.20 0.10 0.20 0.10 0.10 0.10 0.10 0.00

k0.60 0.63 0.43 0.42 0.31 0.31 0.41 0.31 0.30 0.261.00 0.87 0.63 0.61 0.51 0.50 0.59 0.49 0.49 0.441.25 0.99 0.73 0.70 0.62 0.61 0.68 0.60 0.59 0.551.50 1.06 0.79 0.76 0.69 0.67 0.74 0.66 0.65 0.612.00 1.17 0.88 0.83 0.79 0.76 0.81 0.75 0.73 0.702.50 1.23 0.93 0.89 0.86 0.82 0.86 0.81 0.79 0.763.00 1.29 0.98 0.92 0.91 0.87 0.90 0.86 0.84 0.814.00 1.34 1.02 0.96 0.96 0.91 0.94 0.90 0.88 0.85

hR RC 0.70 0.70 0.70 0.70 0.70 0.50 0.50 0.20 0.00RW 0.70 0.50 0.50 0.20 0.20 0.50 0.20 0.20 0.00RF 0.50 0.20 0.10 0.20 0.10 0.10 0.10 0.10 0.00

k'0.60 0.27 0.14 0.14 0.07 0.07 0.11 0.05 0.03 01.00 0.43 0.25 0.25 0.15 0.15 0.19 0.11 0.05 01.25 0.50 0.31 0.30 0.20 0.20 0.23 0.14 0.07 01.50 0.56 0.36 0.35 0.25 0.24 0.26 0.18 0.08 02.00 0.65 0.43 0.42 0.32 0.31 0.30 0.22 0.10 02.50 0.71 0.49 0.47 0.38 0.37 0.34 0.26 0.11 03.00 0.76 0.53 0.51 0.43 0.41 0.36 0.29 0.12 04.00 0.82 0.58 0.55 0.49 0.47 0.40 0.34 0.14 0

k = a . bh (a+b)

k = 1.5 . a . bh' (a+b)

90˚-90˚300

600

900

60˚-60˚

30˚-30˚

1200

A 60 (DIN) I (cd/klm)

ab

h' h

0˚30˚

90˚

-30˚

-90˚150

300

450

600

60˚-60˚

A 40 (DIN) I (cd/klm)

90˚

60˚30˚

-90˚

-60˚ -30˚

100

200

300E 12 (DIN) I (cd/klm)

SEAN MAC
SEAN MAC
1.00 = 0.631.15 = o.691.25 = 0.73
SEAN MAC
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UTILANCE
SEAN MAC
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SEAN MAC
SEAN MAC
SEAN MAC
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3.3 Practical planning3.3.6 Calculations

When the appropriate table has beendrawn up, the room index k can be deter-mined from the room geometry. The uti-lance can then be read off the table fromthe column showing the correspondingroom index and line showing the appro-priate combination of reflectance factorsor, for greater accuracy, calculatedthrough interpolation. The average hori-zontal illuminance is the result of the totalluminous flux produced by all the lampsinstalled per room surface in the space,corrected by the light output ratio (whichis provided by the lighting manufacturer),by the calculated utilance and light lossfactor V, which takes into account theageing of the lighting installation and isusually taken to be 0.8. Should a lightinginstallation consist of several types of lumi-naire of varying classification, e.g. wide-beam lighting provided by louvred lumi-naires and a narrow-beam componentprovided by downlights for incandescentlamps, then the illuminance has to be cal-culated separately for each componentand then added.

There are computer software programsavailable for calculating the utilisationfactor. They not only calculate the illumi-nance, but also locate the appropriatetables and and can handle the complexinterpolation between the individualtables or values contained in the tables, if required.

3.3.6.2 Planning based on specific connec-ted load

Another method of providing the roughdimensioning of a lighting installationderived from the utilisation factor methodis based on the specific connected loadavailable. This method allows the calcula-tion of the required connected load for an average illuminance provided by a givenluminaire and light source, or vice versa,the average illuminance that can be ob-tained given a specific connected loadand a light source.

Planning a lighting installation basedon a specified connected load relies onthe fact that every type light source has aspecific luminous efficacy practically irre-spective of the power consumption.When using the utilisation factor methodit is possible to substitute the overall lu-minous flux by the connected load correc-ted by the respective luminous efficacy.Taking this as a basis it is possible to cal-culate the connected load per m2 which isrequired for a given combination of lumi-naire and light source to obtain an aver-age illuminance of 100 lx in a space withstandardised room geometry and reflec-tance factors. Values obtained in this wayonly apply with accuracy to the particularstandard room. A correction factor mustbe included in the calculations to takeaccount of conditions that deviate fromthe standard.

157

Standard values forspecific connectedload P* for differentlamp types in direct luminaires.

Lighting calculationsbased on a specificconnected load oflamps (P*). Formulae forcalculating the nominal illuminance EN for a given number of lumi-naires, or the numberof luminaires requiredn for a given illumi-nance.

Correction factor f takes into account theeffect of the roomgeometry and the re-flectance factors onthe illuminance ornumber of luminaires.The appropriate value

is calculated from thebasic area A, the roomheight h and the reflec-tance factor of the ceiling (RC), walls (RW)and floor (RF).

Example of a roughcalculation of the illu-minance for a roomwith a combination oftwo different luminairetypes.

Luminaire type 1 (A)

n = 12PL = 100 WP* = 12 · W

m2 · 100 lx

Luminaire type 2 (TC)

n = 9PL = 46 W

(2 · 18 W + ballast)

P* = 4 · Wm2 · 100 lx

EN1 = 9o lxEN2 = 93.2 lxEcom = 183.2 lx

Room data

Length a = 10 m Width b = 10 m Height h = 3 m R = 0.5/0.2/0.1 f = 0.9

Lamp P* (W/m2· 100 lx)

A 12QT 10T 3TC 4HME 5HIT 4

EN (lx) Nominal illuminancen Number of luminairesPL (W) Connected power for one

luminaire incl. control gearP* (W/m2 · 100 lx) Specific connected loadf Correction factora (m) Length of roomb (m) Width of room

f RC 0.70 0.50 0.00RW 0.50 0.20 0.00RF 0.20 0.10 0.00

A (m2) h (m)20 ≤ 3 0.75 0.65 0.6050 0.90 0.80 0.75

≥ 100 1.00 0.90 0.8520 3–5 0.55 0.45 0.4050 0.75 0.65 0.60

≥ 100 0.90 0.80 0.7550 ≥ 5 0.55 0.45 0.40

≥ 100 0.75 0.60 0.60

1 2

n = . P* . EN . a . b100 . PL

1f

EN = f . 100 . n . PLP* . a . b

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h

I

Eh

h

Eh

åIå

Ev

å Iå

d

Ev

å Iå

d

Eh = lh2

Eh = . cos3 ålåh2

Ev = . cos3 (90–å)låd2

Eind = . ®M1–®M

ÏLeAges

[E] = lx[l] = cd[h] = m[d] = m

3.3 Practical planning3.3.6 Calculations

A by-product of this method of calculationis that for each lamp type a typical valuecan be defined for the specific connectedload. This means, for example, that a lu-minous flux of around 20000 lm can beobtained from conventional incandescentlamps with a connected load of 1500 W,without strict regard for whether ten 150 Wlamps, fifteen 100 W lamps or twenty 75 Wlamps are used. The connected power re-quired for specific lamp types can be usedfor rough planning and, above all, toenable a quick comparison to be made ofdifferent light sources.

3.3.6.3 Point illuminance

In contrast to the utilisation factor method,which only allows average illuminancesfor an entire space to be calculated, usingthe inverse square law illuminance levelscan be calculated for specific points in thespace. The results in this case are veryexact, errors only arise if light sources areincorrectly presumed to be point sources.Indirect components are not included in thecalculation, but can be included throughan additional calculation. The calculationof illuminance at specific points can becarried out for the lighting provided by onesingle luminaire or for situations wherethe contribution of several luminaires is tobe taken into account.

The manual calculation of point illu-minance at specific points can be appliedfor the lighting design of confined spacesilluminated by individual luminaires; calcu-lations for numerous points within thespace and a large number of luminairestake too much effort and are not justi-fied. Computer software is generally usedfor calculating the illuminances for anentire space.

The basic function provided by theseprograms is the calculation of illuminan-ces for all room surfaces, working planes orclearly defined zones, in which indirectlighting components are included in thesecalculations. Using this basic data it ispossible to derive further values, such asthe luminance of the illuminated areas,shadow formation or contrast renditionfactors at specific points in the rooms.

Programs of this kind usually offer avariety of possibilities for the graphicpresentation of the results, ranging fromisolux diagrams and isoluminance dia-grams for individual room surfaces or zonesto three-dimensional renderings.

158

Formula for the roughcalculation of the indi-rect illuminance com-ponents (Eind ). Usingthe overall luminousflux produced by all theluminaires installed inthe space ÏLe, the aver-age reflectance RM andthe sum Acom of allroom surfaces.

Calculating illuminanceat specific points. Therelation between illu-minance E at a specificpoint and the luminousintensity I of one lumi-naire (from the top downwards): horizontal

illuminance Eh directlybelow a luminaire. Horizontal illuminanceEh at an angle å to theluminaire. Vertical illu-minance Ev at an angleå to the luminaire.

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Eh

P

A L

h

Eh

P

L

å

Ev

Eh

3.3 Practical planning3.3.6 Calculations

3.3.6.4 Lighting costs

When calculating the costs for a lightinginstallation it is necessary to differentiatebetween the fixed costs and the variablecosts. The fixed costs do not apply to theoperating time of the lighting installation,they comprise the amotised costs for the luminaires, for their installation andcleaning. The variable costs are dependenton the operating time. They comprise costsfor energy, material and wages for staffcarrying out lamp replacement. On thebasis of these values it is possible to cal-culate the different qualities of a lightinginstallation.

The annual costs of a lighting instal-lation are of particular interest. It is oftenadvisable to compare the economic effi-ciency of different lamp types in the plan-ning phase. This data can be calculatedeither as annual costs or as costs for theproduction of a specific quantity of light.The pay-back time is important in bothcompletely new projects and refurbishmentprojects, that is to say the period of timewithin which the operating costs that havebeen saved can be set off against theinvestment costs for the new installation.

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Horizontal illuminanceEh at point P, producedby luminous surface Aof luminance L at angle ™.

Horizontal illuminanceEh at point P, producedby a circular luminoussurface of luminance L,whereby the surfaceextends to an angle 2 å.

Vertical illumnancee Ev,produced by luminanceL from one half of thespace.

Horizontal illuminanceEh, produced by lumi-nance L from one halfof the space.

Formula for calculatingthe costs of a lightinginstallation K from thefixed costs K' and theannual operating costsK".

Formula for calculatingthe pay-back time t of a new installation.

Comparison of thepay-back time t of twonew installations, whereby installation Bhas higher investmentcosts and lower opera-ting costs.

Calculating illumi-nances from the lumi-nance of flat lightsources.

a (DM/kWh) Energy costs K (DM/a) Annual costs for a

lighting installationK' (DM/a) Fixed annual costsK" (DM/a) Annual operating costsK1 (DM) Costs per luminaire incl. mountingK2 (DM) Costs per lamp

incl. lamp replacementK l (DM) Investment costs (n · K1)

n Number of luminairesp (1/a) Interest payments for the installa-

tion (0.1–0.15)P (kW) Wattage per luminaireR (DM/a) Annual cleaning costs

per luminairet (a) Pay-back timetB (h) Annual operating timetLa (h) Service life of a lamp

Eh = . cos4 ™L . Ah2

Eh = ! . L . sin2 å

[E] = lx[l] = cd/m2

[h] = m[A] = m2

K = K' + K''K' = n (p . K1 + R)

K'' = n . tB (a . P + )K2tLa

K = n [p . K1 + R + tB (a . P + )]K2tLa

t = Kl (new)K'' (old) – K'' (new)

t = Kl (B) – Kl (A)K'' (A) – K'' (B)

Eh = ! . L EV = . L!2

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3.3.7 Simulation and presentation

Visual presentations of lighting installationsand the effects they produce in the ar-chitectural space play a significant part inlighting design. There is a wide rangeof possibilities for presenting a lightingconcept ranging from technically orientedceiling plans to graphic illustrationsof varying complexity to computer-aidedrenderings and three-dimensional archi-tectural models or models of the lightinginstallation.

The aim of such presentations is to provide information. This may be by way ofthe technical qualities of a lighting instal-lation, the spatial design or the lightingeffects in the luminous environment.Computer-aided renderings and models canalso be used to simulate the lightingeffects of a planned installation and to gainnew information.

One of the first forms of presentation oflighting installations are technical dra-wings and diagrams. The reflected ceilingplan is the most important. It providesexact information about the type and arrangement of luminaires. This documen-tation can be supplemented by illumi-nance values entered on the ceiling planor isolux diagrams, or additional drawingsshowing different perspectives of theluminous environment. All these help toillustrate the lighting layout and its effectin the space.

Graphic material of this kind allowsthe lighting designer to derive technicalinformation about the installation andgain a realistic impression of the lightingeffects produced. This cannot be expectedof other persons involved in the planningprocess who are not so experienced intechnical or lighting matters. It is thereforeadvisable not always to place too muchreliance on technical documentation whenpresenting a lighting concept.

To illustrate a lighting concept it is there-fore better to opt for presentation materialthat reflects the architecture and thelighting installation and the lighting effectsthat can be expected. From the pointof view of drawings, simple sketches maysuffice. The larger the project, the moredetailed the graphic presentation will haveto be to show the differentiated lightingeffects in the luminous environment.

With the exception of drawings thatare based on existing installations orsimulations, even the more complex formsof representation will reproduce lightingeffects in the form of diagrams, whichdo not demonstrate the complexity of theactual lighting effects. This need notnecessarily be a disadvantage; when ex-plaining an overall concept a simple yeteffective sketch can illustrate the intendedlighting effects much better than an ap-parently realistic representation with arti-ficially staggered luminance levels. In most

3.3 Practical planning3.3.7 Simulation and presentation

cases a drawing is an economical way of presenting an idea, is adaptable and canbe prepared quickly.

Graphically, lighting effects can best beillustrated in the form of beams of light,which either appear as an outline of thebeam, as a coloured area or in a shade of grey that will allow them to stand outagainst a background colour. If luminancepatterns are also to be represented,this can be produced using special shadingtechniques or by free-hand drawingsusing pencil or chalks. If more contrast isrequired in the drawing to be able to re-present a greater range of luminances, thiscan be produced using hand-drawn whitelines against a grey shaded background.For greater differentiation a methodusing backlit transparent paper, a collageof foils with different transmittancequalities provides an extremely broad scaleof luminances from black to the lu-minance of the lightest source applied.

Besides drawings, it is also possible to usecomputer programs to illustrate lightinginstallations and the effects produced.Lighting calculations programs generallycomprise simple spatial representationswith different illuminance levels repre-sented by black/white shading. That is tosay, besides producing lighting data in tables and diagrams computer programsare also able to give a rough visual im-pression of the lighting concept. Creatingmore complex computer graphics with a more differentiated representation ofluminances, colour and the furnishings in the luminous environment requires advanced hardware and software.

Similar to a drawing, computergraphics only provide a simplified pictureof the actual lighting effects; grading luminances too strictly will often give riseto a rigid, artificial impression. In contrastto drawings, computer graphics do notproduce a subjective idea of the lightingeffects that can be expected, but are based on complex calculations; they aretherefore not only a presentation aid, butalso an effective means of simulation.

Although it does take some time toenter the data concerning the archi-tecture, lighting installation and possiblyfurniture, this may be justified because it does allow more flexibility to try outdifferent luminaire types and lightingconcepts. It is frequently advisable to dowithout detailed computer graphics toillustrate the effect of the light in a givenspace and to make drawings based on the lighting data produced by the computercalculations instead.

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Graphic presentationof a lighting concept.

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3.3 Practical planning3.3.7 Simulation and presentation

161

A graphical representa-tion of the lightingconcept for the audito-rium of a theatre. Thelight beams are repre-sented by hand-drawnwhite lines against agrey background. Thepresentation is confi-ned to the representa-tion of luminaire posi-tions, beam directionsand beam spreads.

It conveys a qualitativeoverall impression ofthe distribution oflight in the space anddeliberately providesno quantitative data.

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B'

A'

F

A

B

a

b

S

c

d

D

D'

C'

C

E

B

A DC

F1 F2

G

Ed

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S

3.3 Practical planning3.3.7 Simulation and presentation

162

and bc with the per-spective plane. Base-line G is then selectedand entered to scale in line with vanishingpoints F1 and F2 (eyeheight of a personstanding) together withthe height of point D.Lines DA and DC aredefined by extendingthe vanishing lines F1Dand F2D. The last pointin the perspective, B, is defined by extendingthe vanishing lines F1Aand F2C.

Perspective construc-tion of a lightingstructure (dual-pointperspective): observa-tion point S and per-spective plane E arealso selected first, forreasons of simplifica-tion the perspectiveplane once again liesat the furthermostpoint to the rear of theplan a, b, c, d. The ver-ticals of the perspec-tive are derived fromthe projection ofpoints a, b, c, d on theperspective plane, theverticals of the vani-shing points from thepoints of intersection ofthe parallels to the edges of the plan ba

Central perspective: a perspective drawingis to be created fromthe plan a, b, c, d andthe lighting layoutentered. First, the ob-servation point S andperspective plane E areselected. For reasons ofsimplification, the per-spective plane is iden-tical to the rear wall ofthe space, so thatheights and distancescan be entered to scaleon the rear wall of theperspective; the obser-vation point is locatedon the extension of the left-hand wall. Theverticals of the per-spective are the resultof the projection ofpoints a, b, c, d on theperspective plane. Thenthe base line AD of therear wall is selected in the perspective andthe room height AA',DD' and the height of

the vanishing point AF(in this case eye heightof a person seated) areentered to scale. Thisin turn defines the rearwall. By extending thevanishing lines FD andFD' the right-hand sidewall DC and D'C' isdefined. The horizontalsBC and B'C' completethe perspective as thefront base and ceilinglines. Ceiling grid andluminaire positions inthe perspective are de-rived from the straightlines drawn from va-nishing point F andfrom the projection ofwall points from obser-vation point S on theperspective plane E.

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3.3 Practical planning3.3.7 Simulation and presentation

163

Linear, rectangularrecessed ceiling lumi-naire. Cross section andlongitudinal sectionwith ceiling connection,0°/30°isometric viewfrom below.

Linear, suspended lumi-naire or light structureelement. Cross sectionand longitudinalsection, 0°/30°isometricview.

Circular luminaires.Cross section and iso-metric view of recessedand surface-mounted ceiling luminaires.

Side and front view of a spotlight inclinedat an angle of 30°,0°/30°isometric view.

Illustrations of lumi-naires for technicalpurposes and presen-tation drawings. Indetailed drawings ofluminaires crosssections illustrate the

technical constructionand function of theluminaire, whereas theisometric drawingsillustrate the designand visual impression ofthe luminaire.

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ß

å

3.3 Practical planning3.3.7 Simulation and presentation

164

mately from one an-other; between å and !the resulting angle isusually 10°.

Illustration of lightingeffects in technical descriptions and pre-sentation drawings:diameters of light beams on the floor arethe result of the beamspread !, whereas scallops can be createdon the walls by usingthe cut-off angle !. If only one value isknown, beam spreadand cut-off angle canbe derived approxi-

Cross section of theroom on the luminaireaxis showing cut-offangle å and beamspread ! of the luminai-res.

Plan of the space withreflected ceiling planand diameters of lightbeams, which are defined by the beamspread of the lumi-naires.

Wall elevation withscallops, the heightand pattern defined bythe cut-off angle ofthe luminaires.

Perspective drawing of the space with lumi-naires and lighting effects on the roomsurfaces.

Sectional drawing andwall elevation showinga light beam with a particular beam spread.

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3.3 Practical planning3.3.7 Simulation and presentation

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Calculation and visua-lisation of lightingdata using a computer.

Plan of the room withreflectedceiling planand calculation points. Calculation results re-presented by curves ofidentical illuminanceon the working plane(isolux curves).

Graphic representationillustrating illuminancedistribution in thespace by means of anisometric drawing withilluminance relief representation.

Graphic representationof illuminance distri-bution on the roomsurfaces by means of a perspective represen-tation with isoluxcurves illustrated inshades of grey. Takingreflectance factors intoaccount, similar re-presentations can becreated to indicateluminance distribution.

Simulation of lightingeffects in the spacebased on the spatialdistribution of lumi-nance. A photo-realistic luminancepattern is achievedthrough the fine gra-dation of the lumi-nance values.

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1

2

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2

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166

an adjustable parabolichalogen projector (2)attached to a rotatingswivel arm (1), which iscomputer-controlledto take up the positionof the sun for any location or time of dayor year, or follow thecontinuous path of thesun over the course ofone day at any givenlocation and time ofyear.

Daylight and sunlightequipment in ERCO’slighting laboratory, simulation takes placein a 5 x 5 x 3 m spacewith a central adjust-able table. A textile ceiling illuminatedfrom behind by fluores-cent lamps togetherwith a surroundingmirrored wall serve tosimulate diffuse day-light; the illuminationlevel can be conti-nuously controlled. Directed sunlight is simulated by means of

Principle of a modularsystem for creating simulation models withvariable room geome-try (1:10, 1:20). Withthe aid of support pil-lars ceilings and wallscan be arranged asrequired. Models ofthis type are used fordaylight simulationand for the simulationof artificial lighting.The base of the modelis open to allow light-meters, endoscopesand micro-video came-ras to be inserted.

Adjustable table (3) forvariable positioning ofmodels for sunlightingtests. With the aid ofan integral coordinatedesk (1) luxmeter ele-ments, endoscopes andmicro-video cameras(2) can be computer-controlled to take upany position and direc-tion.

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3.3 Practical planning3.3.7 Simulation and presentation

The use of models for daylight simulationsis particularly widespread. In this case the problem of recreating luminaires toscale does not arise; sunlight and daylightare readily available if the model is takenoutside. The alternative is an artificial skyand a sunlight simulator, which can beused to produce the required effect. In thecase of daylight simulation in the openair, an instrument similar to a sundial isused to position the model to correspondto a specific geographical location at aspecific time of day and year at a specificangle of incident sunlight. If sunlightsimulation equipment is used, the sun isrepresented by a movable, artificial sun. In both cases it is possible to carry outaccurate observations of the effect of thelight in and on the building on small-scale models and make constructive designsfor solar protection and daylight control.Observations can be recorded usingendoscope cameras, while micro videocameras allow the documentation ofchanges in the lighting conditions over thecourse of the day or year.An artificial sky can be used to simulatelighting conditions under an overcast skyand also allows daylight factors to be measured (according to DIN 5034).

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In addition to drawings and computeraidedtechniques the construction of models isa practical way of demonstrating a lightinginstallation and the lighting effects itcreates. Similar to computer graphics, themodel can be used for presentation andsimulation purposes.

The clear advantage of models is thatlighting effects are not only illustrated,but they can actually be shown and ob-served in all their complexity. The degree ofaccuracy of the simulation is only limitedby the size and degree of accuracy of theproportions of the model. The mostrealistic simulations are made on mock-upmodels on a 1:1 scale.

The scale chosen for the model de-pends on the purpose of the test and thedegree of accuracy the simulation is topresent. Models made to scales of 1:100or even 1:200 only allow observation ofthe daylight effect on the entire building,whereas with 1:20 to 1:10 models itis possible to observe detailed lighting effects in individual areas.

The most critical detail, especially onsmall-scale models, is generally the lumi-naire itself, because even small deviationshave a direct effect on the lighting effect.There are similarly limits to the accuracywith which luminaires can be representeddue to the dimensions of the light sourcesavailable. Through the application ofoptical fibres, which convey the light froman external light source to several lumi-naire models, a higher degree of accuracyis possible. When evaluating the effect of a specially developed luminaire or lumi-naires that are integrated into the archi-tecture, it is advisable to create a mock-upof the luminaire, or of the specific ar-chitectural element on a 1:1 scale. This isusually possible without too great an ex-pense, whereas it is only justified for entirerooms in the case of large-scale projects.

Fibre optic system usedto simulate artificiallighting in models ofinterior spaces. Theends of the fibres re-present the individualluminaires in the model. By using specialconstructions on theends of the fibres different luminaire types can be simulated(wide and narrow-beam downlights, directional spotlights,wallwashers and exposed lamps).

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3.3 Practical planning3.3.8 Measuring lighting installations

3.3.8 Measuring lighting installations

Measuring the lighting qualities of alighting installation can serve a number ofpurposes. In the case of new installationsmeasurements are taken to check that theplanned values have been obtained.Measurements recorded on existing instal-lations help the planner to decide whatmaintenance or renovation work is required.Measurements can also be taken duringthe planning process for the evulation andcomparison of lighting concepts. Thefactors that are measured are initially illu-minance and luminance. Other values,such as shadow formation or the contrastrendering factor (CRF) can be obtainedusing appropriate techniques.

To ensure that results of measurementstaken are usable the measuring equip-ment must be of a suitably high quality.In the case of equipment for measuringilluminance this applies predominantly tothe correct measurement of inclined in-cident light (cosine-corrected photometer)and the V (lambda) correction of thephotometer.

When measuring a lighting installation, a series of parameters have to be takeninto account and documented in a report.This initially involves the recording ofspecific qualities of the environment, suchas reflectance factors and colours ofroom surfaces, the time of day, the amountof daylight and the actual mains voltage.Features of the lighting installation arethen recorded: the age of the installation,the lighting layout, the types of lumi-naires, the type and condition of the lampsand the overall condition of the instal-lation. The type of measuring equipmentand the class of accuracy of the measuringdevice has to be recorded.

To record illuminances for an entirespace (in accordance with DIN 5035, Part 6)a floor plan is made of the space andhas to include furniture. The arrangementof luminaires and the points at whichmeasurements are to be taken are thenentered. The measuring points are thecentral points on a 1-2 m grid, in the caseof high rooms up to a 5 m grid. Measure-ments can also be taken at individualworkplaces, in which case an overall tightmeasuring grid is created for the area.Horizontal illuminances are measured atthe individual measuring points at theheight of the working plane of 0.85 m or0.2 m respectively, cylindrical illumi-nances for determining the formation ofshadows on a 1.2 m plane of reference.Luminance measurements for calculatingglare limitation are carried out at work-places in offices at eye level (1.2 or 1.6 m).

168

Measuring horizontalilluminance on theworking plane usingmeasuring equipmentwith an integral photo-cell (1).

Measuring horizontalilluminance using measuring equipmentwith a separatephoto-cell (2)

Measuring cylindricalilluminance using measuring equipmentwith a separatephoto-cell (3)

Measuring the lumi-nance of luminaires orroom surfaces usingmeasuring equipmentwith an integral view finder.

Measuring the contrastrendering factor (CRF)for the evaulation of reflected glare atworkplaces on the basis of a standard reflection value.

2 3

1

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3.3 Practical planning3.3.9 Maintenance

3.3.9 Maintenance

The maintenance of a lighting installationgenerally comprises lamp replacementand the cleaning of the luminaires, andpossibly also re-adjustment or realign-ment of spotlights and movable luminaires.

The main objective of maintenance is toensure that the planned illuminance ismaintained, i. e. to limit the unavoidablereduction of luminous flux of a lightinginstallation. The reasons for the reductionin luminous flux may be defective lampsand the gradual loss of luminous flux bythe lamps or a decrease in light outputdue to soiling of the reflectors or attach-ments. In order to avoid a reduction in luminous flux and illuminance below a given level all lamps must be replaced and luminaires cleaned at regular intervals.It is practical to effect both maintenanceprocedures at the same time, since timeand technical equipment, such as liftingtrucks and cleaning equipment, are essen-tial costly factors in maintenance.

By stipulating a light loss factor whenplanning the lighting, the intervals atwhich maintenance is to be carried out canbe controlled. By keeping light loss fac-tors low the lighting level will initially behigher and the period during which lu-minous flux is gradually reduced to belowthe critical value extended. Using thelight loss factor, lamp replacement and thecleaning of luminaires can be timed totake place simultaneously. In dusty environ-ments, for example, a low light lossfactor can be stipulated (e.g. 0.6 insteadof the customary 0.8) to extend theintervals between the cleaning of the lumi-

naires and co-ordinate them with theservice life of the lamps.

It is advisable to have an adequatesupply of the required lamp types, both forregular and individual lamp replacement.This will ensure that only lamps of the samepower, luminous colour and with thesame technical qualities will be used in thelighting installation. In the case of specificlamp types, e. g. halogen lamps for mainsvoltage, the products supplied by diffe-rent manufacturers deviate so greatly fromone another that uniform lighting effectscan only be obtained if the luminaires areall equipped with the same brand.

Besides quantative issues there are a number of qualitative aspects that maybe decisive for maintenance. When onelamp fails in a geometric arrangement ofdownlights, or in a continous row ofluminaires, it may have little effect on theoverall illuminance in the space, but theinterruption in a pattern of bright lumi-naires may be visually disturbing. This also applies to the effects created by theluminaires; a missing beam of light in aseries along one wall is just as disturbingas an abrupt drop in luminance due to adefective wallwasher. It is therefore morepractical in this case not to wait untilthe regular lamp replacement is due, but toreplace the defective lamp immediately.The adjustment of luminaires is alsoclassified as maintenance in the interestof the qualitative aspects of the lightinginstallation. In the field of display lightingluminaires frequently have to be re-aligned to emphasise specific areas to accommodate the layout of a new arran-gement, or the repositioning of stands, shelves or showcases in retail spaces.

The task of the lighting designer is todraw up a maintenance plan that meetsthe requirements of the given situationand to provide the necessary informationfor the maintenance staff. The mainten-ance plan should enable the operator toservice the installation at regular intervals,checking whether the technical require-ments are being met and the lighting isperforming as planned.

169

Measuring illuminan-ces on the workingplane in empty or openfurnished spaces is made according to aregular grid of 1 to 2metres.

Measuring points forthe measurement of illuminances at work-places.

Formula for calculatingthe average illumi-nance –E from a measu-ring grid with n measu-ring points and themeasured values Ex.Calculating the unifor-mity g of a lightinginstallation from thelowest value Emin andthe average illumi-nance –E.

E— = . Ín

1Ex1

n

g = EminE—

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Examples of lighting concepts

4.0

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Downlight

Track-mounted spotlight

Downlight, asymmetricalwallwasher, washlightDouble washlight

Corner washlight

Square luminaire

Square luminaire,asymmetricalLouvred luminaire

Spotlight, directional spotlight

Louvred luminaire,asymmerical

Light structure with track

Light structure withlouvred luminaireLight structure with pointlight sourcesDownlight withemergency lightingSquare luminaire with emergencylightingLouvred luminaire withemergency lightingSinglet

Light structure

4.0 Examples of lighting concepts

In the preceding chapters qualitativelighting design has been depicted as acomplex process involving the considera-tion of functional, psychological andarchitectural requirements appertainingto specific tasks. When dealing withproject-related design concepts the scopeand limits of a set of standard designexamples soon become apparent.

In fact, standard solutions should beavoided at all costs. They may appear to be easy to transfer to any kind of lightingproject, but they can never meet the requirements of individual, task-relatedsolutions.

Analysing designs that have alreadybeen implemented is equally not easy. It is admittedly possible to demonstratethe various aspects of a differentiated,pur-posefully planned solution taking aspecific project as an example, but it ispractically out of the question to transferthis concept onto another set of task-oriented criteria.

If a handbook of qualitative lightingdesign concepts is to do more thanprovide the technical basics and a list ofplanning requirements, it must limit itselfto presenting general concepts as exam-ples of applications, which will serve as a basis and a source of ideas for planningof greater relevance relating to specificsituations.

The examples of lighting concepts given in this chapter intentionally avoidgoing into detail. This would only be valid for a defined room situation anda prescribed set of tasks. This appliesabove all to the provision of illuminancelevels and exact lamp data. With a fewexcep-tions, floor plans and sections areon a 1:100 scale to provide comparabledimensions of the spaces and lighting in-stallations. The choice of luminaires ispurposefully limited to the standard equip-

ment applicable to architectural lighting.Decorative luminaires and custom de-signed fixtures, as frequently applied withinthe framework of individual concepts, are only found in a few cases.

The aim of presenting these examplesis to provide a series of basic conceptswhich may serve as a basis for a wide va-riety of unique solutions. Considerationhas only been given to the general re-quirements to be observed for a particulararea of planning, which neverthelessincludes the aspects that deserve specialattention regarding planning functional,architectural or perception-orientedlighting. Taking this as a basis, a range ofalternative design concepts have beenproposed that comprise the selection ofappropriate light sources and luminairesand arrangement of equipment in accor-dance with the lighting requirements andthe architectural design.

The task of lighting design is to alignthe stated concepts to the requiredlighting quality, the conditions laid downby the users of the space and the archi-tectural design in every specific case, tomodify them or expand them through the application of decorative luminairesand lighting effects – in short, to usegeneral basic concepts to create individuallighting solutions.

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Luminaire symbolsused in the reflectedceiling plans in thechapter: Examples ofdesign concepts.

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4.0 Examples of lighting concepts4.1 Foyers

4.1 Foyers Foyers are spaces that link a building withthe outside world; they serve as entrancearea, reception and waiting areas, andalso provide access to internal areas of thebuilding. As foyers are usually unfamiliarenvironments, one of the main tasks of thelighting is to provide clear orientation.This means providing calm, non-dramaticambient lighting to elucidate the archi-tectural structure of the space and avoidaccentuating additional structures, whichmay cause confusion. The next task is to draw attention to essential focal areas.

The first of these is the entrance.Attention can be drawn to this area viaincreased illuminance levels. It is also pos-sible to use a different luminous colourhere or an individual arrangement of lu-minaires in the ceiling. Other areas to be accentuated are the reception desk andwaiting areas, entrances to corridors,staircases and lifts.

As a transition zone between the out-side world and the interior of the buildinga foyer should also coordinate the diffe-

rent lighting levels inherent to these twoareas. It may be practical to install alighting control system that can be pro-grammed to handle daytime and night-time requirements. Systems adjusted tothe availability of daylight or user fre-quency can also contribute to the economicefficiency of an installation.

If the foyer has an image function, therequired atmosphere can be achieved viathe purposeful selection of light sourcesand luminaires, or by providing deco-rative sparkle effects and light sculptures.Clear views through the space should not be hampered by confusing structuresor an excess of competing visual stimuli.

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4.0 Examples of lighting concepts4.1 Foyers

Daytime and night-time lighting are clearlydifferent. During the daytime pendantdownlights supplement the daylight pou-ring in through the glazed facade androof. The entrance is accentuated by inte-gral downlights; there is no additionalaccent lighting on the reception desk or inthe waiting area.

After dark the architectural structuresare emphasized by wall-mounted com-bined uplight and downlights and ceilingwashlights. The ambient lighting is produ-ced by reflected light, with accent lightingon the entrance.

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Pendant downlight forHIT lamps.

Combined uplight/downlight for halogenlamps or compact fluorescent lamps.

Ceiling washlights forhalogen lamps or com-pact fluorescent lamps.

Recessed downlightsfor low-voltage halogen lamps.

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4.0 Examples of lighting concepts4.1 Foyers

A suspended light structure carries thelighting equipment. During the daytime thelobby is lit by daylight, with the wallbehind the reception desk illuminated bywallwashers and the entrance accentua-ted by downlights. The area beneath thefirst floor ceiling is illuminated using surface-mounted downlights.

The accent lighting is maintained at night, and is supplemented by an illu-mination of the room surfaces by indirectluminaires mounted on the light struc-ture. The reception desk has received indi-vidual lighting from task lights.

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Light structure withintegral indirect lumi-naires for fluorescentlamps and integraltrack to take wall-washers.

Surface-mounted downlight for compactfluorescent lamps.

Recessed downlight for low-voltage halogenlamps.

Task light for compactfluorescent lamps.

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4.0 Examples of lighting concepts4.1 Foyers

The luminaires are mounted on a load-bearing lattice beam with integral track.The reception desk is accentuated byspotlights, the entrance by downlights.Ambient lighting and the accentuating ofarchitectural structures is effected byflush-mounted ceiling panels with wall-washers. The waiting area beneath the first floor ceiling is illuminated by wall-washers mounted on a track recessed in the ceiling.

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Load-bearing latticebeam with integraltrack to take spotlightsor panels with wall-washers equipped withPAR 38 reflector lamps.

Track for wallwashersfor halogen lamps.

Recessed downlight for low-voltage halogenlamps.

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4.0 Examples of lighting concepts4.1 Foyers

Recessed double focus downlights alongboth end walls provide ambient lighting.The entrance is accentuated by recesseddownlights, the reception desk by track-mounted spotlights; projectors are usedto create lighting effects on the wall. The area beneath the first floor ceiling isilluminated by recessed downlights.

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Double-focus down-light for metal halidelamps or halogenlamps.

Recessed downlight for low-voltage halogenlamps.

Track with spotlightsand projectors.

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4.0 Examples of lighting concepts4.1 Foyers

The luminaires are mounted on a wide-span lighting structure. A series of minia-ture low-voltage halogen lamps make for specular effects on the lower side ofthe structure. After dark the architecture is accentuated by integral, indirect luminai-res, with additional accent providedby spotlights. Downlights accentuate theentrance and the edge of the first floorceiling.

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Wide-span system with track-mounted spotlights, miniaturelow-voltage lamps onthe lower side of thestructure and integralindirect luminaires for fluorescent lamps.

Recessed downlight for low-voltage halogenlamps.

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4.0 Examples of lighting concepts4.1 Foyers

Recessed wallwashers illuminate the long walls, with reflected light creating theambient lighting. The reception deskhas received individual lighting using tasklights. Additional accentuation of theentrance is effected by downlights. The area beneath the first floor ceilingis illuminated by recessed washlights.

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Decorative recesseddownlight for low-voltage halogen lamps.

Recessed wallwasherfor PAR 38 reflectorlamps.

Recessed washlight forgeneral service lamps.

Task light for compactfluorescent lamps.

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4.0 Examples of lighting concepts4.2 Lift lobbies

4.2 Lift lobbies People have to be able to find lifts quickly,which is why lift lobbies should be illu-minated so that they stand out from theirsurroundings. Accentuation can be effec-ted by means of independent lighting ele-ments or by concentrating larger numbersof the elements that provide the lightingin the surrounding area around the lift lobby.The lighting inside the lift car shouldalso harmonize with the overall lightingconcept to avoid glare or any unreaso-nable changes in brightness when enteringor leaving the lift.

The lighting in lift lobbies and liftsshould provide an adequate vertical com-ponent to facilitate communication andrecognition when the doors open. Verticallighting components should be achievedusing wide-beam luminaires with adequatecut-off angles or by indirect lighting; this presumes that there is adequate reflec-tance from the room surfaces, especiallythe walls.

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Downlights for compact fluorescent lampsprovide economically efficient generallighting. Low-voltage downlights have beenused to accentuate the lift lobby. Thedownlights provide horizontal lighting andproduce effective grazing light over thelift doors.

Indirect luminaires illuminate the lift lobby.The area directly in front of the lifts isaccentuated by wall-mounted downlights.The grazing light over the walls creates an interesting architectural feature andprovides diffuse lighting.

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Recessed downlight for compact fluorescentlamps.

Pendant indirect lumi-naire for fluorescentlamps.

Wall-mounted down-light for halogen reflector lamps.

Recessed downlight for low-voltage halogenlamps.

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4.0 Examples of lighting concepts4.2 Lift lobbies

The objective is to create a prestigiousatmosphere. The area directly in front of thelifts is accented by means of speculareffects produced by a series of miniaturelamps and downlights arranged in pairs.Both lighting components are mounted ona suspended track system.

General lighting is provided by wall-mounted ceiling washlights. The lift doorsare accentuated using recessed louvredluminaires for fluorescent lamps.

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Louvred luminaire forfluorescent lamps.

Wall-mounted ceilingwashlight for compactfluorescent lamps orhalogen lamps.

Track system with miniature lamps and a double row ofdownlights for halogenreflector lamps.

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4.0 Examples of lighting concepts4.2 Lift lobbies

General lighting is provided by a staggeredarrangement of decorative downlights,which produce adequate illuminance levelsand attractive specular effects. In addi-tion, lighting at floor level is provided bya series of floor washlights.

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Recessed floor wash-light for compact fluorescent lamp.

Decorative recesseddownlight for low-voltage halogen lamps.

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4.0 Examples of lighting concepts4.3 Corridors

Corridors provide access to differentrooms or constitute a link between partsof buildings. They may receive daylightthrough windows or skylights, but fre-quently run through the interior of buil-dings and have to be lit artificially all day.

One of the main tasks of the lightingin corridors, like foyers, is to provide clearorientation. Non-dramatic, communica-tive lighting is required here to express thearchitectural structure of the space.Central points of interest, such as entrance,exit and doors to adjacent rooms shouldreceive additonal accentuation to ensurethat the user is supplied with the neces-sary information. If the design of thebuilding is such that it is difficult to find

the way from place to place, it is advisableto assist orientation by means of infor-mation signs, symbols or colours.

Corridors located in the interior of abuilding are often dark or appear thesame. This effect can be counteracted byilluminating the walls and providinglighting that structures the space, makingit more easily legible. In such corridors it is advisable to arrange luminaires in ac-cordance with the architectural design.Accent lighting can also contribute towardsremoving the feeling of monotony in the space, by dividing it up into sectionsor views.Continous lighting in corridors inevitablyleads to long switching times, which

means that ways have to be found to saveenergy. One means is the use lamps withhigh luminous efficacy, such as fluorescentlamps. In buildings where corridorsalso have to be lit at night, it is advisableto include night lighting in the designconcept, and reduce the lighting level fortimes of when the corridors are lessfrequently used. This may be effected bydimming, switching specific groups ofluminaires off or by installing a speciallydesigned night lighting system.

4.3 Corridors

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Recessed downlights provide generallighting in the corridor of a hotel withstaggered arrangement of doors. The area around the doors is accentuated byrecessed louvred luminaires.

Washlights for recessed mounting illumi-nate the circulation zones. The extremelydiffuse light they produce lends the spacea bright and friendly atmosphere. Down-lights are positioned above the doors toaccentuate the area around the doors.

General lighting is provided by floor washlights. The areas around the doors areaccentuated by downlights mounted onthe side walls. This produces a clear con-trast between the horizontal lightingin the circulation zone and the verticallighting in the area around the doors.

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Recessed washlightsfor halogen lamps.

Wall-mounted down-light for compact fluorescent lamps.

Floor washlight forcompact fluorescentlamps.

Recessed downlight for compact fluorescentlamps.

Recessed downlight for compact fluorescentlamps.

Recessed louvredluminaire for fluore-scent lamps.

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Wall-mounted ceiling washlights provideuniform, indirect lighting in the corridor,which makes for a bright and friendly atmosphere.

The corridor lighting in an administrationbuilding is provided by a matching seriesof bracket-mounted wallwashers. Theseprovide both indirect ambient lighting viathe light reflected by the walls and directlighting of information signage.

A light structure spanned between thewalls provides indirect light for the ambientlighting. The luminaires are arranged sothat an information sign can be aligned toeach door.

4.0 Examples of lighting concepts4.3 Corridors

186

Wall-mounted ceilingwashlights for com-pact fluorescent lampsor halogen lamps.

Bracket-mounted wall-washers for fluorescentlamps.

Light structure withindirect luminaires for fluorescent lamps,and information signs.

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4.0 Examples of lighting concepts4.3 Corridors

Economically efficient corridor lighting by means of a regular arrangement of lou-vred luminaires equipped with compactfluorescent lamps.

The lighting components are mounted ona multifunctional trunking system thatruns the length of the corridor and takesdirect luminaires, sections of track forspotlights to accentuate specific wallareas, plus loudspeakers and emergencylighting.

Recessed louvred luminaires make foruniform, efficient lighting. The luminairesare arranged crosswise to the length ofthe corridor.

187

Recessed louvredluminaire for compact fluorescent lamps.

Trunking system withrecessed louvred lumi-naires for fluorescentlamps, and track-mounted spotlights.

Recessed louvredluminaire for fluore-scent lamps.

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4.0 Examples of lighting concepts4.4 Staircases

4.4 Staircases The primary objective of staircase lightingis to provide an aid to orientation. Light is used to make the structure of the envi-ronment legible and hazardous areasvisible, without creating any additional,confusing structures. The structure of the staircase should be easily recognizable,and the individual steps clearly visible.Since staircases are usually illuminated forlong periods of times, it is advisable touse energy-saving light sources.

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4.0 Examples of lighting concepts4.4 Staircases

Pairs of recessed louvred luminaires illu-minate the landings and flights of stairs.

Direct and indirect luminares in a lightstructure suspended in the stairwell.The structure follows the course of the stair-cases and crosses the landings betweeneach flight of stairs. This avoids any com-plicated constructions above the centre of the landings.

189

Recessed louvred lumi-naire for compact fluorescent lamps.

Suspended light struc-ture with integral di-rect or indirect lumi-naires for fluorescentlamps.

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4.0 Examples of lighting concepts4.4 Staircases

A direct-indirect light structure spannedbetween the walls of the stairwell abovethe landings provides direct and reflectedlight for the lighting of the adjacentflights of steps.

A direct-indirect wall-mounted luminaireprovides adequate lighting levels on thestairs and landings.

190

Light structure withintegral direct-indirectluminaires for fluore-scent lamps.

Wall-mounted direct-indirect luminaire for fluorescent lamps.

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4.0 Examples of lighting concepts4.4 Staircases

Two different types of luminaire are usedto illuminate the flights of stairs and landings. Floor washlights provide thelighting for the flights of stairs, whereasthe landings are illuminated by recesseddownlights.

Wall-mounted downlights installed abovethe foot and top of each flight of stairsand above the doors on the landings illu-minate the staircases. This arrangementof luminaires produces excellent visualconditions. Mounting the luminaires onthe walls also makes this lighting solutionsuitable for open staircases, where instal-lation can sometimes be difficult.

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Floor washlight forcompact fluorescentlamps.

Recessed downlight for compact fluorescentlamps.

Wall-mounted down-light for compact fluorescent lamps.

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4.0 Examples of lighting concepts4.5 Team offices

4.5 Team offices The lighting of team offices for smallgroups is required to fulfil a number ofconditions, as laid down in the standardsfor the lighting of workplaces. The re-quirements include the following qualitycriteria: the level and uniformity of thelighting, luminance distribution, limitationof direct and reflected glare, the directionof light and shadow, luminous colour andcolour rendering.

Other requirements that may have to be met may concern the correlation ofdaylight and artificial light, the presenceof drawing boards, and above all the lightingof spaces with personal computers. Lumi-nances in the space should be balanced andspecial attention paid to optimum glarecontrol through the installation of suitableluminaires. The luminaires used for thelighting of spaces with personal computersare required to meet especially stringentstandards to avoid reflected glare oncomputer screens. Luminaires constructedin accordance with the standards arereferred to in Germany as VDT-approvedluminaires and can be used withoutreservation for the illumination of suchworkplaces. It should be pointed out,however, that VDT-approved luminairesdo have the following disadvantages in spite of their glare limiting qualities:the low vertical lighting they produce, the fact that the luminaires have to bearranged in close proximity to one another,and the increased reflected glare onhorizontal visual tasks. For the lighting ofspaces with positive image screens or if luminaires are installed outside the cri-tical area of the screens, it is advisable to install wide-angle luminares and satin finished reflectors, and to only use theVDT-approved fixtures as a solution for themost critical cases concerning the lightingof personal computers.

One way of lighting team offices is to provide uniform illumination using lumi-naires arranged according to a set grid,where character and glare limitation canbe influenced by the choice of luminairesand whether they are direct, indirect ordirect-indirect fixtures. Another possibilityis to provide equally uniform, but lowerambient lighting supplemented by tasklights. For team offices which are clearlysubdivided into individual areas (workingarea, circulation zone, social area, confe-rence area) it is possible to develop azonal concept, lighting each area in accor-dance with the activity that takes placethere. By switching different combinationsof luminares the lighting can be adjustedto suit the use of the space, e.g. by combi-ning luminaires for fluorescent lampsand halogen lamps. It is also possible toprovide daylight-related switching of lu-minaires located near windows.

For economically efficient lightingit is advisable to use conventional or com-pact fluorescent lamps. Efficiency can be further increased by the use of electroniccontrol gear, which also enhances visualcomfort through the avoidance of flick-ering effects.

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4.0 Examples of lighting concepts4.5 Team offices

A regular arrangement of recessed louvredluminaires for the ambient lighting. The lighting is not related to individualworkplaces, which means that officelayouts can be changed without changingthe lighting.

A staggered arrangement of recessedlouvred luminaires provides uniform am-bient lighting. A linear prismatic lenspositioned in the centre of the reflectorproduces batwing-shaped light distri-bution, which completely avoids reflectedglare, achieves good CRF values through-out the space and allows flexible furniturelayout.

194

Recessed louvredluminaire for compact fluorescent lamps.

Recessed louvredluminaire for fluore-scent lamps.

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4.0 Examples of lighting concepts4.5 Team offices

A regluar arrangement of recessed down-lights with cross-blade louvres providesuniform ambient lighting.

The lighting components are mounted onmultifunctional channels that run parallelto the windows. They take the louvred luminaires for the ambient lighting and directional spotlights for accent lighting.Ventilation or air-handling systems can beintegrated into these installation channels.

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Recessed downlightwith cross-blade louvrefor compact fluore-scent lamps.

Trunking system/instal-lation channel forlouvred luminaires forfluorescent lamps and recessed directionalspotlights for halogenlamps.

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4.0 Examples of lighting concepts4.5 Team offices

Secondary reflector luminares are used toilluminate the office. The ratio of directand indirect light and glare limitation canbe controlled by the appropriate choice of luminaires. This will in turn produce therequired atmosphere.

Diffuse, glare-free ambient lighting pro-duced from free-standing ceiling wash-lights. In addition, each workplace has itsown task light.

196

Direct-indirect secon-dary reflector lumi-naires for recessed mounting into ceilingsfor fluorescent lamps.

Free-standing ceilingwashlight for metalhalide lamps.

Task light for compactfluorescent lamps.

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4.0 Examples of lighting concepts4.5 Team offices

The lighting is provided by a suspendedlight structure, which takes both direct-indirect luminaires and downlights. Thiscombination allows efficient lightingusing fluorescent lamps for office workduring the day, and low-voltage down-lights for meetings that may take place atthe end of the day.

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Suspended light struc-ture with integral, direct-indirect lumi-naires for fluorescentlamps, and integral downlights for low-voltage halogen lamps.

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4.0 Examples of lighting concepts4.6 Cellular offices

4.6 Cellular offices The same design criteria basically applyfor cellular offices as for team offices. Foroffices with a high daylight componentlower illuminances are sufficient; it is alsoadvisable to install the luminaires so thatfixtures near the windows can be switchedseparately when there is sufficient day-light available.

Whereas in the case of team offices it can be of extreme importance to controlthe luminance of luminaires, especially in spaces with personal computers, thisaspect is not so critical in cellular officesdue to the geometry of the space. Distur-bing glare, especially reflected glare ondisplay screens, may however be caused bythe windows.

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Ambient lighting is provided by louvredluminaires for fluorescent lamps arrangedparallel to the window. The lighting lay-out is workplace-related, with lower illumi-nance in the circulation area between the doors. The wide-angle luminaires make for en-hanced contrast rendition; the direct light component is reduced by the linearprismatic lens.

Integral direct-indirect luminares forfluorescent lamps and track-mounted spot-lights mounted on a light structure sus-pended in the space. The ambient lightingis workplace-related and is produced bythe luminaires for fluorescent lamps. Thespotlights are used to accent points of interest on the walls.

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Recessed louvred lumi-naires for fluorescentlamps.

Suspended light struc-ture with integral direct-indirect lumi-naires for fluorescentlamps and integraltrack-mounted spot-lights.

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4.0 Examples of lighting concepts4.6 Cellular offices

General lighting is provided by recessedsecondary reflector luminaires. The ratio ofdirect and indirect light and glare limita-tion can be controlled by the appropriatechoice of luminaires, which in turn pro-duces the required atmosphere.

Ambient lighting is provided by a preciselypositioned group of four downlights with cross-blade louvres for compact fluorescent lamps.

Office lighting using louvred luminaires forcompact fluorescent lamps. A linearprismatic lens can be inserted above thecross-blade louvre. This produces batwinglight distribution, which in turn leads toenhanced contrast rendition.

200

Secondary reflector luminaire for recessedmounting for fluores-cent lamps.

Recessed downlightwith cross-blade louvre for compact fluorescent lamps.

Recessed louvredluminaire for compactfluorescent lamps.

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4.0 Examples of lighting concepts4.6 Cellular offices

Wall-mounted ceiling washlights provideindirect ambient lighting and create abright and friendly atmosphere in the space.A task light on the desk provides directlight on the working plane when required.

Track system spanned from wall to wall withlow-brightness luminaires as well asspotlights for the accentuation of specificpoints of interest or importance.

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Wall-mounted ceilingwashlight for fluore-scent lamps or compactfluorescent lamps.

Task light for compactfluorescent lamps.

Track system with low-brightness luminairesfor fluorescent lamps,and spotlights.

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4.0 Examples of lighting concepts4.6 Cellular offices

The ambient lighting in the office is provi-ded by four recessed indirect secondaryreflector luminaires. The indirect compo-nent is reflected into the space by thesatin finished reflector. The luminaire lay-out is workplace-related with lowerilluminance in the circulation area.

Office lighting illuminance is provided by two suspended light structure elementsparallel to the windows, with integral direct-indirect luminaires and integral directional luminaires to accentuate thedesk and other points of interest.

202

Recessed secondaryreflector luminaires forcompact fluorescentlamps.

Light structure withintegral direct-indirectluminaires for fluore-scent lamps and down-lights for low-voltagehalogen lamps.

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4.0 Examples of lighting concepts4.7 Executive offices

4.7 Executive offices An office of this kind may be the work-place of a manager or the office of a self-employed person. It consists of a workingarea and conference area, each area withspecific lighting requirements.In contrast to the purely functional lightingin the other office spaces, atmosphereand prestigious effect are also importantaspects in this case.As rooms of this kind are used for a varietyof activities, it is advisable to develop adesign concept that allows the switchingand dimming of different groups of lu-minaires to meet changing requirements.

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4.0 Examples of lighting concepts4.6 Executive offices

Recessed downlights arranged in a rec-tangle around the perimeter of the roomprovide ambient lighting. A task light isinstalled on the desk.

Washlights on the end walls provide thegeneral lighting in the room. The desk receives direct light from two directionalspotlights. A group of four downlights accentuate the conference table.

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Task light for compactfluorescent lamps.

Recessed downlight forgeneral service lamps.

Recessed downlight for low-voltage halogenlamps.

Recessed directionalspotlight for halogenreflector lamps.

Recessed wallwasherfor general servicelamps.

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4.0 Examples of lighting concepts4.6 Executive offices

The lighting equipment is mounted onthree multifunctional channels that runparallel to the windows. They contain two louvred luminaires for the lighting ofthe desk, downlights for the illuminationof the desk and conference table and direc-tional spotlights to illuminate the cup-boards. Outlets are available for spotlightsfor the illumination of the remaining wallsurfaces.

Wallwashers aligned with the cupboardsprovide the ambient lighting. The deskhas a task light, a double-focus downlightaccentuates the conference table. Sur-face-mounted spotlights pick out pointsof interest on the remaining wall surfaces.

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Recessed louvredluminaire for fluore-scent lamps.

Recessed directionalspotlight for halogenlamps.

Recessed downlight forhalogen lamps.

Recessed wallwasherfor halogen lamps.

Recessed double-focusdownlight for low-voltage halogen lamps.

Task light for compactfluorescent lamps.

Singlet with spotlight.

Singlet with spotlight.

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4.0 Examples of lighting concepts4.8 Executive offices

Recessed louvred luminaires illuminatedesk and conference table. Track-mountedwallwashers provide vertical lighting onthe end walls and produce a bright andfriendly atmosphere.

Recessed washlights provide uniformlighting of the wall lined with cupboardsand one of the end walls; the reflectedlight also provides the ambient lighting.Desk and conference table are accentua-ted by spotlights mounted on a recessedtrack. Other points of interest are pickedout by further spotlights.

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Track-mounted wall-washers equipped withhalogen lamps.

Recessed louvredluminaire for fluore-scent lamps.

Recessed washlightsand corner washlights for general servicelamps.

Track with spotlights.

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4.0 Examples of lighting concepts4.8 Conference rooms

4.8 Conference rooms Conference rooms are used for a varietyof purposes: for discussions, seminars,small-scale presentations, or even a wor-king lunch. The lighting design conceptmust therefore be multifunctional andinclude the possibility of creating aprestigious atmosphere.Conference lighting requires a balancedratio of horizontal and vertical lighting.Horizontal lighting makes for good shapingqualities and and adequate bright-ness.Vertical components produce a bright andfriendly atmosphere and promote com-munication. Extreme direct or diffuse lightconditions should be avoided.

The presentation of pictures, products,notes made on the board or on a flip-chartrequire additional accent lighting on the end walls of the conference room. Thelighting on the walls must be reduced to a suitable level to allow people to writeby when slides or overhead foils areprojected. It is therefore practical to plan alighting installation comprising circuitswhich can be switched and dimmed sepa-rately, or even a programmable lightingcontrol system, which allows preprogram-med scenes to be recalled at the touch of a button.

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Ceiling washlights provide indirect lightfor the general lighting of the room. Theend walls can be illuminated by track-mounted spotlights or washlights, if re-quired. Two rows of recessed downlightsprovide direct light on the table, whichcan serve as the main lighting for a working lunch or dinner, or for people towrite by when slides are being shown.

Secondary luminaires arranged along theside walls provide general lighting withbalanced horizontal and vertical compo-nents. The luminaire design, which har-monizes with the geometry of the spacemakes for optimum control of direct andreflected glare. Two rows of downlights forrecessed mounting in the ceiling providedirect, prestigious light on the table,which can serve as the main lighting fora working lunch or dinner, or for peopleto write by when slides are being shown.Track-mounted spotlights in front ofthe end walls can be used to accentuatevisual aids.

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Track with spotlights.

Wall-mounted ceilingwashlight for halogenlamps.

Recessed downlight for halogen lamps orgeneral service lamps.

Recessed downlight forlow-voltage lamps.

Integral secondaryluminaire for fluore-scent lamps.

Track with spotlights.

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4.0 Examples of lighting concepts4.8 Conference rooms

Direct-indirect luminaires suspendedabove the table provide ambient lightingin line with the layout or the officefurniture. Downlights arranged along theside walls brighten the overall environ-ment. The end walls can receive additionallighting via wallwashers; luminairesalong the side walls can be dimmed toprovide lower lighting levels, for example,for people to write by when slides arebeing shown.

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Pendant direct-indirect luminaire forfluorescent lamps.

Recessed wallwasherfor fluorescent lamps.

Recessed downlight for halogen lamps orgeneral service lamps.

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4.0 Examples of lighting concepts4.8 Conference rooms

The lighting is installed in a suspendedceiling positioned at a set distance to thewalls. The light consists of two rows oflow-voltage downlights, which producespecular effects on the surface of the table.These downlights comprise the mainlighting on representative occasions orlight for people to write by in the case ofslide projections. Above the edge of theceiling there are tracks with washlights forindirect lighting, and spotlights. Thespotlights and the washlights, which havefluorescent lamps, adjacent to the sideand end walls can be switched and dim-med separately.

Washlights provide direct lighting over thetable and ambient lighting by the lightreflected by the walls. The luminaires areequipped with general service lamps,which means that they can be easily dim-med to the required lighting level; the alignment of the lighting to the seatingensures optimum visual comfort. Thepairs of luminaires nearest the end wallscan be switched separately for projectionlighting. Tracks mounted parallel to the endwalls can take spotlights for the illumi-nation of the walls or presentations.

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Track with spotlightsand wallwashers forfluorescent lamps.

Recessed downlightsfor low-voltage lamps.

Downlight for generalservice lamps.

Track with spotlights.

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4.0 Examples of lighting concepts4.8 Conference rooms

Luminaires equipped with fluorescentlamps and mounted on a suspended lightstructure provide the lighting over the table. Dimmable wallwashers for halogenlamps are mounted on the end sections.Spotlights accentuate points of interest onthe walls. The latter can be dimmedduring slides projections to provide lightto write by.

211

Light structure withlouvred luminares forfluorescent lamps,wallwashers for halo-gen lamps and spot-lights.

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4.0 Examples of lighting concepts4.8 Conference rooms

General lighting in the conference roomis provided by a series of wallwashers. Downlights equipped with general servicelamps provide light to write by. Tracksmounted parallel to the end walls can takespotlights for the illumination of thewalls or demonstrations.

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Recessed downlight forgeneral service lamps.

Track with spotlights.

Recessed wallwasherfor fluorescent lamps.

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4.0 Examples of lighting concepts4.9 Auditoriums

4.9 Auditoriums Auditoriums are rooms that can be usedto give a variety of talks or presentations toan audience. They may be used simply for the presentation of special papers, fortalks supported by slide, film or videoprojectors, or overhead projectors, for ex-perimental demonstrations and productpresentations or for podium discussions andseminars. Lighting for auditoriums shouldtherefore be based on a multi-functionalconcept which allows the lighting to be adapted to meet a variety of differentrequirements.

The main feature of the lighting inauditoriums is the functional separation ofspeaker’s platform from the audience. On the speaker’s platform the lighting isfocussed on the speaker, or on the objectsor experiments presented. When overheadfoils, slides, films and videos are shownthe lighting must be reduced – especiallythe vertical lighting on the end wall – soas not to interfere with the projections.

In the area where the audience are seatedthe lighting primarily serves the purpose of orientation and allows people to takenotes. During slide projections and thelike the lighting is reduced to a level forpeople to write by. It is important thatthe lighting should allow eye contact be-tween the speakers and the audience, and between the people in the audience,to allow and promote discussion, inter-action and feedback.

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Recessed wallwashers illuminate the endwall of the auditorium. Downlights thatcan be switched and dimmed separatelyplus a series of singlets for additionalspotlights provide accent lighting on thespeaker’s platform.

The lighting over the seating areaconsists of two components. Downlightsfor compact fluorescent lamps arrangedin a staggered pattern provide ambientlighting during the talk. A series ofdimmable downlights for halogen lampsare arranged between the first setof downlights and provide controllablelighting when slides are being shown.Both luminaire types can be operated se-parately or in unison.

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Recessed downlight-wallwasher for PAR 38reflector lamps.

Singlet with spotlight.

Recessed downlight for compact fluorescentlamps.

Recessed downlight forhalogen lamps.

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A row of wallwashers illuminate the endwall. The speaker’s platform is accentuatedby track-mounted spotlights.

Wallwashers arranged along the sidewalls provide light for orientation. There isalso a series of recessed double-focus downlights for halogen lamps arranged ina regular pattern across the ceiling. Thisset provides lighting during the talk andcan be dimmed down to allow people to take notes during slide or video projec-tions.

The ambient lighting in the auditorium is provided by louvred luminaires alignedto the long side walls and a series ofdimmable downlights in alternate rowsbetween them. This pattern is continued on the speaker’s platform in a condensedform. The end wall receives additionallighting from a series of wallwashers.Singlets along the side walls can take additional spotlights to accentuate specialpoints of interest, if required.

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Recessed double-focusdownlight for halogenlamps.

Recessed wallwasherfor halogen lamps.

Recessed louvred lumi-naire for fluorescentlamps.

Downlight-wallwasherfor general servicelamps.

Singlet with spotlight.

Recessed downlight forgeneral service lamps.

Track with spotlights.

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4.0 Examples of lighting concepts4.9 Auditoriums

Two runs of track over the speaker’s areatake wallwashers for the illumination of the end wall and spotlights for accentlighting.

Floor washlights positioned along oneside wall in the auditorium sectionprovide lighting for orientation. The mainlighting is provided by a suspended lightstructure with direct-indirect luminairesfor fluorescent lamps and dimmable downlights for low-voltage halogen lamps.

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Track with spotlightsand wallwashers for halogen lamps.

Suspended light struc-ture with integral direct-indirect lumi-naires for fluorescentlamps and integral downlights for low-voltage halogen lamps.

Wall-mounted floorwashlight for compactfluorescent lamps.

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4.0 Examples of lighting concepts4.10 Canteens

4.10 Canteens Canteens are spaces where large numbersof people are provided with meals. Thefood is generally served from a counter;people eating in canteens are only therefor a short period of time. The lightingdesign concept should also allow for thespace to be used for other functions suchas parties or meetings.

The prime objective is to provide anefficient lighting installation with highaverage illuminance levels. The atmospherein the room should be bright and friendlywith sufficient vertical lighting to make fora communicative atmosphere. It is ad-visable to plan a second component thatcan be switched separately when brilliant,warm white light is required for festivelighting for a party or a large gathering.

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The lighting is provided from a suspendedlight structure. The ambient lighting comes from luminaires for fluorescentlamps mounted beneath the structure.Spotlights are mounted in track below thelight structure to provide accent lightingover the counter.

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Light structure withluminaires for fluores-cent lamps and integraltrack for spotlights.

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4.0 Examples of lighting concepts4.10 Canteens

A staggered arrangement of square louvredluminaires equipped with compact fluo-rescent lamps provide efficient ambientlighting. A series of recessed downlights for halogen lamps arranged alternately be-tween the louvred luminaires create a prestigious atmosphere. The louvred lu-minaires and the downlights canbe switched separately or in unison.

A combination of fluorescent and halogenlighting. The fixtures used are louvredluminaires equipped with conventionalfluorescent lamps and arranged in parallelrows throughout the space. The counterarea is accentuated by positioning the luminaires closer together.

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Recessed louvred luminaire for compactfluorescent lamps.

Recessed downlight forhalogen lamps.

Recessed louvredluminaire for fluore-scent lamps.

Recessed downlight forhalogen lamps.

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4.0 Examples of lighting concepts4.10 Canteens

Efficient, uniform lighting of the canteen is achieved by direct-indirect luminairesequipped with fluorescent lamps and mounted on a suspended light structurearranged in parallel rows throughout the space.

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Suspended light struc-ture with direct-indirectluminaires for fluore-scent lamps.

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4.0 Examples of lighting concepts4.11 Cafés, bistros

4.11 Cafés, bistros The term café, or bistro, covers a varietyof catering establishments that offer aservice somewhere between the functionalcanteen and the up-market restaurant; a spectrum ranging from fast food restau-rant to ice-cream parlours and cafés to bistros. The clientele comprises smallgroups who tend to stay for longerperiods of time, using the establishmentas a meeting place as well as somewhere to eat.

In contrast to the canteen, the lightingrequired in this case is of a more pre-stigious nature, the lighting level on thewhole lower. The interior design and the accentuation of the individual tablesis more important here than efficient,overall lighting. The objective neverthelessis not to produce very low ambientlighting with strongly illuminated and welldefined individual areas (tables); theentire space should be generally bright andfriendly and promote a communicative

atmosphere. The actual lighting designconcept depends to a large extent on therequired atmosphere and the target clien-tele. It may range from uniform lightingconcepts to the integration of dramaticforms of lighting and lighting effects.

Cafés and bistros are open through-out the day, which results in differentlighting requirements by day and by night.It is therefore advisable to develop aconcept that allows different componentsto be switched and dimmed separately, or to include a programmable lightingcontrol system.

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Three rows of track are proposed to runthe length of the space. Wallwashers aremounted on the track nearest the wall,producing reflected light for the ambientlighting. Spotlights are mounted on thetrack aligned with with the position of thetables. The counter is accentuated by arow of decorative downlights installed ina suspended ceiling.

Ceiling-mounted light structure with direct luminaires arranged in a diagonalpattern across the ceiling provides thelighting on the tables. Surface-mounteddownlights accentuate the counter. A series of singlets along one side wall allow the installation of spotlights to pick out focal points.

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Track with spotlightsand wallwashers.

Decorative recesseddownlight for low-voltage halogen lamps.

Surface-mounted downlight for halogenlamps.

Surface-mounted lightstructure with directluminaires for fluore-scent lamps.

Singlet for spotlights.

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4.0 Examples of lighting concepts4.11 Cafés, bistros

A series of directional spotlights aremounted on installation channels arrangedacross the width of the room. Theseprovide lighting over the individual tablesand accentuate the counter.

Integral directional spotlights arranged in a regular pattern across the ceilingaccentuate the tables. The counter is em-phasized by a linear arrangement ofdecorative downlights.

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Installation channelwith directional low-voltage spotlights.

Integral directionalspotlight for low-voltage halogen lamps.

Decorative recesseddownlight for low-voltage halogen lamps.

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4.0 Examples of lighting concepts4.11 Cafés, bistros

Recessed wallwashers produce reflectedlight for the general lighting in the space.Recessed double-focus downlightsprovide direct light on the tables. The twocomponents are arranged in a regularpattern. The counter is accentuated bydownlights.

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Recessed wallwasherfor halogen lamps.

Recessed double-focusdownlight for low-voltage halogen lamps.

Recessed downlight for low-voltage halogenlamps.

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4.0 Examples of lighting concepts4.12 Restaurants

4.12 Restaurants The difference between restaurants andcafés and bistros lies in the quality andrange of food offered and in the atmos-phere. Lunches and dinners comprisingseveral courses mean that guests generallystay for longer periods of time. Peopledining require a pleasant, prestigious at-mosphere in which to enjoy their foodand conversation with friends or businesscolleagues. Guests also require an ele-ment of privacy in a restaurant. The inte-rior furnishings and the lighting shouldbe chosen and designed to limit visualand acoustic disturbance caused by occu-pants in other parts of the room. Eachgroup of guests should have the feelingthat they have their own private space.

The design concept should thereforeaim to provide illumination that allowsthe surroundings, food and guests to beseen in their most favourable light.

The average illuminance level is low, thegeneral lighting gives way to localisedcelebratory lighting of the individual tables.Paintings, plants or other decorativeelements may be accentuated to createpoints of interest in the environment.“Play of brilliance” in the form of candle-light, decorative luminaires or lightsculptures can also be extremely effectivein the restaurant environment.

To meet the different requirements fordaytime and night-time lighting, it isadvisable to develop a concept that allowsthe switching and dimming of differentgroups of luminaires.

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The ambient lighting in the restaurant isprovided by decorative wall-mountedwallwashers. The tables are illuminated byrecessed directional spotlights; decorativerecessed downlights accentuate the barand the entrance area. Uplights locatedbetween the plants project a leafy patternon the ceiling.

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Decorative recesseddownlight for low-voltage halogen lamps.

Directional spotlightfor low-voltage halogenlamps.

Uplight for PAR 38 reflector lamps.

Decorative wallmountedceiling washlight forgeneral service lamps.

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The indirect general lighting in the entranceand seating area is provided by wall-washers. A regular arrangement of double-focus downlights provide direct lightthroughout the main restaurant area. Asupplementary row of directional spot-lights illuminate the plants between theseated area and the bar. The bar is accentuated by a series of downlights thatfollow the shape of the bar.

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Recessed wallwasherfor halogen lamps.

Recessed downlight for low-voltage halogenlamps.

Recessed directionalspotlights for low-voltage halogen lamps.

Recessed double-focusdownlight for low-voltage halogen lamps.

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4.0 Examples of lighting concepts4.12 Restaurants

Indirect general lighting is provided byceiling washlights arranged along the sidewalls. A staggered layout of decorative recessed downlights provides accentlighting on the tables and bar. Track-mounted spotlights illuminate the plantsand entrance area.

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Wall-mounted ceilingwashlight for halogenlamps or general servicelamps.

Decorative recesseddownlight for low-voltage halogen lamps.

Track-mountedspotlights.

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4.0 Examples of lighting concepts4.13 Multifunctional spaces

4.13 Multifunctional spaces Multifunctional spaces are used as meetingrooms for a variety of events. They can be found in hotels and congress centres,in public buildings and on industrialpremises. They are most frequently usedfor conferences and seminars, but also forreceptions and parties. A multifunctionalspace can often be divided by means ofa removable partition, which allows anumber of small meetings or events to takeplace simultaneously; this requires alighting layout that is symmetrically alignedto the dividing line, in relation to boththe overall space and to the potential in-dividual spaces.

The lighting should be variable tocorrespond to the multifunctional natureof the space. It should be both functionaland prestigious. The lighting installationwill generally comprise several compo-nents, which can be switched or electro-nically controlled separately or in unison.Functional, efficient ambient lighting can

be provided by louvred luminaires equippedwith fluorescent lamps, for example, withadjustable spotlights for the presentationof products or teaching aids and down-lights for general service lamps for accentlighting or dimmed lighting. Dependingon the design of the space, decorative lu-minaires may be used for effect.

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Multifunctional spaces are used fora variety of events. The lighting in thesespaces is not only expected to be func-tional, but also suitable for presentationsand festive occasions. Rooms that can be divided require special attention whendesigning the lighting installation.

Two lighting layouts comprising squarelouvred luminaires designed for compactfluorescent lamps and downlights equippedwith halogen lamps produce both efficientand accentuated, dimmable lighting.

Two runs of track mounted flush withthe ceiling at both ends of the room takespotlights for lighting presentations or astage area. The twin lighting layout allowsthe room to be divided and both partsused separately.

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Seminar.

Recessed louvredluminaire for compact fluorescent lamps.

Double-focus down-light for halogen lamps.

Track with spotlights.

Conference. Gala dinner withindividual tables and buffet.

Gala event withcabaret and dance floor.

Simultaneous use:small party and meeting.

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The ambient lighting in the multifunc-tional space is produced by a symmetrical arrangement of luminaires in both parts of the room. Downlights equipped withcompact fluorescent lamps and pairs of double-focus downlights with halogenlamps are arranged in a uniform pattern.The fluorescent downlights provide efficientlighting for functional events, whereasthe dimmable halogendownlights are usedfor lighting festive occasions and providelighting for people to take notes duringslide or video presentations.

Recessed track with spotlights forpresentation lighting or accent lighting.

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Recessed downlightwith cross baffles forcompact fluorescentlamps.

Recessed double-focusdownlight for halogenlamps.

Track with spotlights.

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4.0 Examples of lighting concepts4.13 Multifunctional spaces

The ambient lighting in the multifunc-tional space is produced by three parallel lines of luminaires that run the length of the room and consist of an alternatingarrangement of louvred luminairesequipped with fluorescent lamps anddownlights with general service lamps.Wallwashers located along the end wallsprovide lighting over the wall surfaces.Four downlights are arranged along thewalls, combined with two singlets for additional spotlights for accent lighting.

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Recessed louvredluminaire for fluore-scent lamps.

Singlet with spotlight.

Recessed downlight forgeneral service lamps.

Recessed wallwasherfor general servicelamps.

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4.0 Examples of lighting concepts4.13 Multifunctional spaces

The lighting is carried on four rectangular,symmetrically aligned suspended lightstructures. The ambient lighting is producedby uplights, with direct light on thetables and floor produced by pairs of down-lights. Spotlights can also be mounted on the structure, if required, to emphasizefocal points on the walls.

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Light structure withuplights designed forcompact fluorescentlamps, downlights forhalogen lamps, andtrack-mounted spot-lights.

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4.0 Examples of lighting concepts4.13 Multifunctional spaces

Ambient lighting in the multifunctionalspace is produced by indirect luminairesmounted on six linear light structuresinstalled across the width of the space. Downlights for halogen lamps are arran-ged between the suspended structures.These downlights can be dimmed for specialoccasions or for people to take notesduring slide or video presentations. Singletsarranged along the side walls take spot-lights for accent lighting, if required.

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Suspended light struc-ture with indirect luminaires for fluore-scent lamps.

Recessed downlight forhalogen lamps.

Singlet with spotlight.

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4.0 Examples of lighting concepts4.13 Multifunctional spaces

The lighting layout in this multifunctionalspace is based on a regular grid, with downlights illuminating the centre of thespace and washlights arranged along the end walls. The track installed betweenthe rows of luminaires take additionalspotlights for accent lighting. The down-lights and washlights are equipped withhalogen lamps, which makes for a presti-gious atmosphere; individual groups ofluminaires can be dimmed to allow thelighting to be adjusted to different requi-rements.

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Recessed washlight forhalogen lamps.

Recessed downlight forhalogen lamps.

Track-mounted spotlights.

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4.0 Examples of lighting concepts4.14 Museums, showcases

4.14 Museums, showcases In many museums, especially those wherearchaeological, ethnological or scientificinformation is presented, the exhibits areprimarily displayed in showcases. Whendeveloping the lighting design concept theshowcases must be treated as the priority.The architecural lighting in this case is of secondary importance. It is importantto avoid creating competition to theobjects on display by over-accentuatingarchitectural elements in the surroun-dings.

The first task of the lighting is toilluminate the exhibits in accordance withtheir particular qualities. It may be theform or structure, the glossy or transparentquality of surfaces or colour that are ofparticular significance and therefore requirepurposefully designed lighting – this mayinvolve diffuse or accent lighting, orlighting with especially good colour ren-dering qualities.

Apart from pure presentation, curato-rial aspects also play an essential part in the development of the lighting designconcept. Depending on the type of ma-terials that are to be illuminated, choice oflamp, filtering and illuminance controlmust be investigated carefully so as not toaccelerate the damage to the exhibits.Apart from loading damage caused by visiblelight, ultraviolet and infrared radiation,overheating in showcases due to convec-tion is also an aspect to be considered; in the case of sensitive exhibits it may benecessary to install integral luminaires in a separate compartment of the showcase.

The recommended illuminance formuseum lighting is 150 lx. This value refersto the lighting of oil paintings and a largenumber of other materials. Less sensitivematerials, such as stone and metal, can be subjected to higher illuminances; toensure that the contrast to adjacent spacesthat are lit at a lower illuminance level is not too strong, it is advisable to take300 lx as the limit. In the case of highlysensitive materials, especially books, water-colour paintings or textiles 50 lx shouldbe regarded as the maximum; this requirescareful balancing of the exhibitionlighting and the ambient lighting, thelatter being considerably lower.

When lighting showcases it is especiallyimportant to avoid reflected glareon horizontal and vertical glass surfaces.Careful attention must be paid to thepositioning and direction of luminaireswhen illuminating the showcase from theoutside. Potential reflected glare throughwindows should also be taken into account and, if necessary, eliminated bythe provision of adequate shielding (e.g. vertical blinds).

High showcases can be illuminated withthe aid of lighting components integratedinto the case soffit. Transparent materials – e. g. glassware – can be illuminated bylighting integrated into the base of theshowcase. As light sources, halogen lampsare generally used for accent lightingand compact fluorescent lamps for wide-area lighting. Fibre optic systems can alsobe of value if thermal load and danger to exhibits due to lamps inside the casesare to be avoided, or if the showcase di-mensions do not allow the installation ofconventional luminaires.

In addition to integral showcaselighting separate ambient lighting is inva-riably required. Depending on the requi-red atmosphere and the illuminance laiddown in curatorial stipulations ambientlighting may range from a lighting leveljust above the level of the showcaselighting down to orientation light producedby spill light from the showcases.

When lighting showcases from the out-side, exhibition lighting and the ambientlighting both come from the ceiling. Thisform of lighting is especially suitable forglass showcases and flat display casesviewed from above, where it is not possibleto integrate luminaires inside the cases.Both daylight and general lighting can con-tribute towards the illumination ofexhibits, as can light from spotlights, allrequiring consideration in the accentua-tion of specific objects. The lighting layoutmust be related to the position of the showcases to avoid reflected glare.Fixed luminaires can only be used incombination with fixed showcases, forexample; in spaces where temporaryexhibitions are held it is advisable to choosean adjustable lighting system, e.g. track-mounted spotlights.

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4.0 Examples of lighting concepts4.14 Museums, showcases

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The lighting in the tall showcases is pro-duced by integral luminaires. Recessed downlights provide ambient lighting andlighting for the flat display cases. The downlights have a narrow beam spreadfor better control of reflections on theglass surfaces of the cases.

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Downlight for low-voltage halogen lamps.

Accent lighting insidethe showcase is pro-vided by recessed low-voltage directionalspotlights. The lumi-naires are equippedwith covered reflectorlamps to avoid dangerto the exhibits.

Showcase lightingusing spotlights. Theshowcase is shielded by a filter attachmentand an anti-dazzlescreen. The upper sec-tion of the showcasecan be ventilated sepa-rately.

Wide-beam lighting ofthe showcase using awashlight for compactfluorescent lamps orhalogen lamps.

Recessed downlight for incandescent lampsor halogen lamps.

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4.0 Examples of lighting concepts4.14 Museums, showcases

Lighting of glass showcases. A series of spotlights are mounted on a suspendedlight structure. This solution also providesambient lighting.

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Showcase lighting usinga fibre optic system.One central light sourcesupplies a number of light heads. Integrallighting of this kindcan be installed in thesmallest of spaces.

Track-mounted spot-lights. The spotlightscan be equipped withfilters to reduce UVand IR radiation, or witha variety of anti-dazzlescreens to limit glare.

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4.0 Examples of lighting concepts4.14 Museums, showcases

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Identifying the “forbid-den zones” for verticalreflecting surfaces.Windows must also betaken into account andshielded, if necessary.

Identifying the “forbid-den zones” for horizon-tal reflecting surfaces.No lamp luminancesshould be reproducedon the reflecting surfa-ces from these areas of the ceiling. It isacceptable to positionluminaires in theseareas, provided theyare directed or shieldedso as not to produceglare effects.

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4.0 Examples of lighting concepts4.14 Museums, galleries

4.15 Museums, galleries In contrast to museums which primarilyexhibit objects in showcases, in gallerieswhere paintings and sculptures areon display architectural lighting is also anessential part of the lighting designconcept. In both historical buildings andmodern museums the architecture isfrequently in competition with the exhibits.The objective of the lighting designconcept will usually be to continue tobalance the importance of the art to thearchitecture.

Museums frequently also use daylightas well as artificial lighting. The lightingdesign concept must aim to control thedaylight and coordinate the natural lightwith the artificial lighting. Daylight can be controlled by the architecture to a cer-tain extent; supplementary devices andequipment may be necessary to controlilluminance in accordance with specificcuratorial stipulations. Electronic controlsystems are now available that allowcombined control of incident daylight usingadjustable louvres as well as the artificiallighting, when daylight is excessive or in-adequate. The lighting system shouldprovide appropriate levels of illuminanceat all times of day and night.

The exhibits to be illuminated aremainly paintings and drawings on the wallsand sculptures in the centre of the spaces.The works of art on the walls can be illu-minated by uniform wall lighting providedby wallwashers or accent lighting usingspotlights. In both cases it is imperative tomake sure that the angle of incidence hasbeen calcuated correctly to avoid distur-bing reflections on glass or shiny surfaces.An angle of incidence of 30° to the ver-tical (angle of incidence for museums) hasbeen proven to be a good guideline,because it handles reflected glare, illumi-nance and frame shadows optimally.Sculptures generally require directed lightto reveal their three-dimensional qualityand surface structure. They are usually il-luminated by spotlights or recesseddirectional spotlights.

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The lighting installation consists of asuspended light structure with uplightsproviding indirect ambient lighting andwallwashers providing direct lighting ofthe walls.

Daylit museum with a luminous ceiling.Wallwashers mounted parallel to the lumi-nous ceiling supplement daylight andprovide lighting in the hours after dark.Track-mounted spotlights allow addi-tional accent lighting.

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Light structure withuplights for compactfluorescent lamps or halogen lamps andwallwashers forPAR 38 reflector lamps.

Track with spotlights.

Wallwasher for fluore-scent lamps.

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4.0 Examples of lighting concepts4.14 Museums, galleries

The lighting of a historical museum buil-ding. As it is not permissible to mount luminaires on the walls or ceiling, thelighting is produced by free-standingwashlights which provide lighting of the walls and the ceiling.

Luminaires mounted on the cornice con-sist of a wallwasher component and aprismatic louvre in the upper part of theluminaire, which directs light onto theceiling.

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Free-standingwashlight for halogenlamps.

Museum luminaire for fluorescent lamps,equipped with awallwasher reflectorand prismatic louvre for the lighting of the ceiling.

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4.0 Examples of lighting concepts4.14 Museums, galleries

The lighting is installed in a suspendedceiling and positioned at a specific distancefrom the walls. Wallwashers are mountedon track behind the edge of the suspendedceiling; the alternating arrangement ofwallwashers for halogen lamps and fluore-scent lamps means it is possible to pro-duce different lighting levels and lightingqualities on the walls. Recessed direc-tional spotlights are installed in the suspen-ded ceiling for the lighting of sculptures.

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Wallwasher for halogenlamps and wallwasherfor fluorescent lamps,both track-mounted.

Recessed directionalspotlight for reflectorlamps.

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The lighting is provided by a rectangulararrangement of wallwashers for fluores-cent lamps, supplemented by a regulararrangment of downlights for halogenlamps. A series of singlets allow additionalaccent lighting using spotlights.

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Wallwasher for fluore-scent lamps.

Recessed downlight forhalogen lamps.

Singlet with spotlight.

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4.0 Examples of lighting concepts4.14 Museums, galleries

Wallwashers arranged parallel to the walls provide lighting of the walls. Trackinstalled in a square in the central areatakes spotlights for accent lighting.

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Recessed wallwasherfor halogen lamps.

Track-mounted spotlights.

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4.0 Examples of lighting concepts4.14 Museums, galleries

Museum lighting based on a luminous ceiling illuminated using fluorescent lamps.Track runs around the edges of the lumi-nous ceiling and crosswise across the cei-ling. This allows the lighting to be supple-mented by spotlights and washlights, asrequired.

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Track-mounted spot-lights and washlights.

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4.0 Examples of lighting concepts4.14 Museums, galleries

The lighting is installed on recessed trackarranged in two superimposed rectangles.The outer track takes wallwashers forthe uniform lighting of the walls, the innertrack spotlights for the accentuationof sculptures. The alternating arrangementof wallwashers for halogen lamps andfluorescent lamps means it is possible toproduce different lighting levels andlighting qualities on the walls.

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Wallwasher for halogenlamps and wallwasherfor fluorescent lamps,both track-mounted.

Track-mounted spotlights.

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4.0 Examples of lighting concepts4.16 Vaulted ceilings

4.16 Vaulted ceilings Vaulted ceilings are usually found in historical buildings. As a rule, one of themain tasks of the lighting, therefore, is to express the architectural design and architectural elements, e.g. by illumina-ting the structure of the ceiling or thefrescos. The design concept will incor-porate indirect or direct-indirect lighting,which will in turn serve to illuminate thearchitecture and provide ambient lighting.

Since penetration of the historicalceiling surfaces is to be avoided, integrallighting or systems that are complicatedto install are out of the question. Thelighting is therefore generally installed onpillars and walls or, alternatively, isapplied in the form of pendant luminairesand light structures.

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A square suspended light structure withuplights for indirect lighting is installed in each vault. Spotlights can be mountedon the lower part of the structure for accent lighting.

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Light structure withuplights for halogenlamps and track-mounted spotlights.

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4.0 Examples of lighting concepts4.16 Vaulted ceilings

The vaulted ceiling is illuminated by com-bined up/downlight luminaires mountedon the pillars. Each free-standing pillar hasfour luminaires and each pilaster oneluminaire. This provides sufficient ambientlighting to make the architecture visible,and for visitors’ and users’ orientation.

When only indirect, uniform lighting of thevaulted ceiling is required this can beachieved using ceiling washlights mountedon the pillars. If installation on the pillarspresents a problem, free-standing lumi-naires can be used.

Groups of four ceiling washlights are mounted on a suspended light structureinstalled on the central axis of the vaults.These washlights provide indirect lighting.Spotlights can be mounted on the lowerpart of the structure for accent lightingpurposes.

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Light structure withpairs of ceiling wash-lights for halogen lampsplus track-mountedspotlights.

Free-standing orwallmounted ceilingwashlights for halogenlamps or metal halidelamps.

Combined up and downlight for halogenlamps.

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4.0 Examples of lighting concepts4.17 Sales areas, boutiques

4.17 Sales areas, boutiques When developing lighting design conceptsfor boutiques or similar sales areas thetasks that require attention are accentlighting for the presentation of goods, anattractive entrance area, and ambientlighting. The lighting of the cash-desk asa workplace should be treated separately.

In general it can be stated that the level of lighting increases with the qualityof the goods and the more exclusive thelocation; at the same time the generallighting is reduced in favour of differen-tiated lighting. Cheaper articles can be displayed under uniform, efficientlighting, whereas high-quality goods re-quire presentation using accent lighting.

As opposed to standard installed loads of15W/m2 for ambient and accent lightingrespectively, the connected load with highlevels of accent lighting may amount toover 60 W/m2.

The lighting design concept will fre-quently go beyond the standard reper-toire of lighting effects and luminaires inorder to create a characteristic atmos-phere. Dramatic lighting effects, such ascoloured light or projection lighting, are also possible, as are distinctive lightstructures or decorative luminaires.

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The ambient lighting in the boutique isprovided by a group of six recessed down-lights; low-voltage downlights arrangedclosely together accentuate the entrance“welcome mat”. Track-mounted spotlightsprovide accent lighting in shop-windows,on shelves and for displays. The cash-desk, treated as a workplace, is additionallyilluminated by a track-mounted spotlight,making it easier for customers to find.

The lighting of the boutique is based on a regular layout, in which two componentsare arranged in a staggered pattern. Thedownlight component provides uniformambient lighting, the second componentconsists of pairs of directional spotlightsfor accent lighting of the shelves and dis-plays. The shop-window displays are il-luminated separately using track-mountedspotlights.

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Recessed downlight formetal halide lamps.

Track with spotlightsfor metal halide lampsand low-voltage halo-gen lamps.

Recessed directionalspotlight for low-voltage halogen lamps.

Recessed downlight for compact fluorescentlamps.

Track-mounted spotlights.

Recessed downlight for low-voltage halogenlamps.

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4.0 Examples of lighting concepts4.17 Sales areas, boutiques

This project has been given an architecturallighting concept. Integral directionalwashlights are mounted in a suspendedceiling installed around the walls. In thecentral area are a series of light structuresarranged parallel to each other withintegral, indirect luminaires. Spotlights arefitted in the track for accent lighting of garments and cash-desk. Shop-windowdisplays are illuminated by track-mountedspotlights.

Directional spotlights are recessed into an L-shaped suspending ceiling to produceaccent lighting on the walls. A doubleportal comprising a lattice beam structurewith integral track is a main feature in the boutique and takes spotlights toaccentuate displays. Shop-windowdisplays are illuminated by track-mountedspotlights.

In the centre of the area lens projec-tors create special lighting effects on thewall or floor (e.g. coloured beams of light,patterns or a company logo). A series ofdownlights accentuate the entrance areaand create a “welcome mat” effect.

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Light structure withintegral indirect lumi-naires for fluorescentlamps and spotlightsmounted on integraltrack.

Track-mounted spotlights.

Recessed directionalwallwasher for metalhalide lamps, high-pressure sodium lampsor halogen lamps.

Recessed directionalspotlight for low-voltage halogen lamps.

Lattice beam structurewith integral track for the mounting ofspotlights and lensprojectors.

Downlight for low-voltage halogen lamps.

Track-mounted spotlights.

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4.0 Examples of lighting concepts4.17 Sales areas, boutiques

The ambient lighting in the boutique isprovided by two light structures runningthe length of the space and equippedwith indirect luminaires for the lighting ofthe shallow ceiling vaults. Three runs oftrack are recessed in the ceiling parallel tothe light structures and take spotlightsfor accent lighting on shelves and displays.Two groups of six directional spotlightsprovide accent lighting in the shop-window.

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Light structure withindirect luminaires forfluorescent lamps.

Directional spotlightfor low-voltage halogen lamps.

Track-mounted spotlights.

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4.0 Examples of lighting concepts4.18 Sales areas, counters

4.18 Sales areas, counters Sales areas where customers are served bystaff at counters are mainly found inretail outlets where customers require con-sultation, e.g. a jeweller’s shop. Thecounter itself creates a dividing elementin the space, the resulting areas eachrequiring their own lighting. The main cir-culation area requires general lighting.Shelves or showcases require vertical dis-play lighting, the counter itself glare-freehorizontal lighting.

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The lighting is mounted on a suspendedlight structure. Ambient lighting is providedby indirect luminaires. Spotlights moun-ted on the structure accentuate shelvesand counter; spotlights mounted on aseparate track provide direct lighting inthe shop-window.

Recessed downlights with various beamangles illuminate the entrance and thecounter. The shelves are accentuated bydirectional floodlights and directionalspotlights; track-mounted spotlights pro-vide direct lighting in the shop-window.

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Recessed downlight for low-voltage halogenlamps.

Recessed directionalspotlight for halogenlamps.

Track-mounted spotlights.

Directional floodlightfor compact fluorescentlamps.

Light structure withindirect luminaires for fluorescent lamps,and spotlights.

Track-mounted spotlights.

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4.0 Examples of lighting concepts4.18 Sales areas, counters

The lighting is mounted in a U-shaped installation channel. Symmetrical louvredluminaires provide the ambient lighting,asymmetrical louvred luminaires the ver-tical lighting of the shelves, and additionaldirectional spotlights accent lighting onspecial offers. Track-mounted spotlightsprovide direct lighting in the shop-window.

The lighting is mounted on a suspendedlight structure. Panels are inserted in thestructure above the counter which take decorative downlights. Spotlights are usedto accentuate shelves and focal points on the walls. Spotlights mounted on a se-parate track provide direct lighting in the shop-window.

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Installation channelwith direct lightingfrom recessed louvredluminaires for fluore-scent lamps and directional spotlightsfor low-voltage halo-gen lamps.

Recessed wallwasherfor fluorescent lamps.

Track-mounted spotlights.

Light structure withpanels, decorativerecessed downlights forlow-voltage halogenlamps and tracks withspotlights for low-voltage halogen lamps.

Track-mounted spotlights.

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4.0 Examples of lighting concepts4.19 Administration buildings,

public areas

4.19 Administration buildings, public areas

Spaces where office space and publicareas meet can be found in a wide varietyof buildings: local authorities, insurancecompanies or banks. There is usually acounter or a row of individual countersbetween the public area and the officespace.

Both room areas and the counter area itself require specific lighting. Thelighting in the public area can be compa-red with that in a lobby, whereas thelighting in the office area must meet therequirements of the workplaces. It is ad-visable that the lighting over the counter

matches the shape and marks it clearly. If direct access is available from the street– as is often the case with banks – the lighting of the entrance area must betreated as a separate lighting entity.

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public areas

The public area is illuminated by a stag-gered layout of downlights. The entrancearea is illuminated separately, also bydownlights. Lighting for the office area isprovided by square louvred luminiaresarranged in a regular pattern across theceiling. A light structure with direct louvred luminaires is suspended above theservice counter; task lights provide addi-tional lighting on the information desk.Spotlights mounted on the light structureaccentuate focal points.

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Recessed louvredluminaire for compact fluorescent lamps.

Recessed downlight for compact fluorescentlamps.

Recessed downlight formetal halide lamps.

Light structure withlouvred luminaires for fluorescent lampsand spotlights.

Task light for compactfluorescent lamps.

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4.0 Examples of lighting concepts4.19 Administration buildings,

public areas

The public area is illuminated by wash-lights, with additional downlights accen-tutating the entrance. The office area isilluminated by a staggered arrangementof louvred luminaires. A light structurewith direct-indirect louvred luminaires issuspended above the counter.

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Recessed louvredluminaire for fluore-scent lamps.

Light structure with direct-indirect louvredluminaires for fluore-scent lamps.

Recessed washlight forhalogen lamps.

Recessed downlight forhalogen lamps.

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4.0 Examples of lighting concepts4.19 Administration buildings,

public areas

Pairs of combined up/downlights are in-stalled along the one side wall. They provideindirect light and the beams of light theyproduce subdivide the wall. Downlights positioned in front of thecounter produce increased illuminance.Decorative downlights create a “welcomemat” effect in the entrance area. A lightstructure with luminaires equipped withfluorescent lamps is suspended above thecounter. The office area is illuminated by a staggered arrangement of downlightswith cross baffles.

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Light structure withluminaires for fluore-scent lamps.

Recessed downlight forhalogen lamps.

Wall-mounted com-bined up/downlight forPAR 38 reflector lamps.

Recessed downlightwith cross baffles forcompact fluorescentlamps.

Decorative recesseddownlight for low-voltage halogen lamps.

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4.0 Examples of lighting concepts4.19 Administration buildings,

public areas

The indirect lighting in the public area isprovided by ceiling washlights. A series ofdownlights in the entrance area create a“welcome mat” effect. A suspended ceiling with integral downlights followsthe course of the counter. The office areais illuminated by a light structure arran-ged diagonally to the main axis and fittedwith direct-indirect louvred luminaires.

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Recessed downlight for low-voltage halogenlamps.

Wall-mounted ceilingwashlight for halogenlamps.

Light structure with direct-indirect louvredluminaires for fluore-scent lamps.

Recessed downlight formetal halide lamps.

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4.0 Examples of lighting concepts4.20 Exhibitions

4.20 Exhibitions A frequent task of exhibition lighting is to create defined presentation area withina larger space. This kind of lighting isfrequently required in halls or pavilions attrade fairs, at airports and other travelterminals. Such areas are used for the ex-hibition of specific products in depart-ment stores or car showrooms, or even forfashion shows in hotels or congresscentres.

Since it is usually a case of providingtemporary lighting, sometimes onlyfor a few days, it is advisable to go for ademountable, adaptable construction on which to install the lighting. Modularlattice beam structures meet theserequirements best. They can be erectedirrespective of the surrounding archi-tecture, and varied in size and shape dueto their modular construction. It is mostcustomary to use load-bearing structuresonto which luminaires can be mountedmechanically. Structures with integral trackare practical because they save having to wire the structure; integral track allowsa large number of luminaires to bemounted and controlled easily.

Power tripods present an especially ver-satile solution, which allows lighting tobe set up quickly and easily.

As in the case of all exhibitionlighting accent lighting is by far the moreimportant component; ambient lightingthat also serves as the base lighting for thesurrounding architecture is usually onlyrequired on stands at trade fairs. Spotlightsand projectors are the luminaires mostcommonly used. They produce direct lightand excellent colour rendering, whichemphasises the qualities of the materialson display. Stage effects can also be used for presentation lighting, e.g. colouredlight or projections; the lighting designmay consist of a comprehensive range ofdesign possibilities – irrespective of thesetting or the objects being presented.

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The lighting is mounted on a wide-spanlight structure with textile ceiling elements.The structure takes direct luminairesdesigned for fluorescent lamps and smalldecorative lamps and spotlights foraccent lighting.

265

Wide-span light struc-ture with luminairesfor fluorescent lamps, small decorative lampsand track-mountedspotlights.

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4.0 Examples of lighting concepts4.20 Exhibitions

Spotlights mounted on a power tripodsmake for variable exhibition lighting.

The lighting is installed on a double portalframe structure comprising lattice beamswith integral tracks aligned diagonally tothe presentation space. Spotlights andprojectors are used for striking accentlighting, clearly defined beams and goboprojections.

266

Power tripod withspotlights.

Lens projectors andspotlights mounted onlattice beams withintegral tracks.

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4.0 Examples of lighting concepts4.20 Exhibitions

The lighting is installed on a freestanding,wide-span structure comprising latticebeams with integral tracks. Spotlights andprojectors are used for striking accentlighting and clearly defined beams andgobo projections.

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Lens projectors andspotlights mounted on lattice beams with integral tracks.

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Appendix5.0

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5.0 AppendixIlluminancerecommendations

Illuminancerecommendations

270

Space/ activity Recommended Light sourcemin. illuminance

E (lx)

Office 300 T, TCTeam office 500 TOpen plan office 750 T, TCTechnical drawing office 750 T, TCData processing 500 T, TCCAD 200/500 A, QT, T, TCControl room 200 TCCorridor 50 TCStaircase 100 T, TCCanteen 200 A, QT, QT-LV, TCBathroom, WC 100 T, TC

Sales area 300 QT, QT-LV, T, TC, HST, HSE, HITDepartment store 300 QT, QT-LV, T, TC, HST, HSE, HITCashdesk 500 T, TCSupermarket 500 T, HITReception 200 A, QT, QT-LV, TCRestaurant 200 A, PAR, R, QT, QT-LV, TCCafé, bistro 200 A, PAR, R, QT, QT-LV, TCSelf-service restaurant 300 T, TCCanteen kitchen 500 TMuseum, gallery 200 A, PAR, R, QT, QT-LV, T, TCExhibition space 300 PAR, R, QT, QT-LV, T, TC, HST, HSE, HITTrade fair hall 300 T, HME, HITLibrary, media library 300 T, TCReading room 500 T, TCGymnasium, competition 400 T, HME, HIE, HITGymnasium, training 200 T, HME, HIE, HITLaboratory 500 TBeauty salon 750 QT, QT-LV, T, TCHairdressing salon 500 T, TCHospital, ward 100 T, TC– ambient lighting– reading light 200 A, QT-LV, T, TC– examination light 300 QT, T, TCHospital, examination 500 T

Reception, lobby 100 QT, T, TCCirculation area 200 QT, T, TCClassroom 300/500 T, TCLarge classoom 750 T, TCCollege hall 500 T, TCArt studio 500 T, TCLaboratory 500 T, TCLecture hall, auditorium 500 QT, T, TCMulti-purpose space 300 QT, T, TCConcert, theatre, festival hall 300 A, PAR, R, QTConcert platform 750 PAR, R, QTMeeting room 300 A, QT, TCChurch 200 A, PAR, R, QT

Recommended mini-mum illuminances (E)for typical interiorlighting tasks. The illu-minances are aimed ata lighting level appro-priate to the specificvisual tasks to be per-formed in the space orin a part of the space.They do not include architectural lightingcomponents or other

aspects for the specificsituation. The averagehorizontal illuminancesquoted are in accor-dance with nationaland international stan-dards. Using the lightsources indicatedlighting qualities canbe achieved to meetthe requirements ofthe particular visualtask economically.

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271

Classification of lamps

I Incandescent lampH High-pressure discharge lampL Low-pressure discharge lamp

General service lamp (I) (G) A AParabolic reflector lamp (I) (G) PAR PARReflector lamp (I) (G) R PARHalogen reflector lamp (I) Q R QRHalogen lamp (tubular form) (I) Q T QTMercury lamp (ellipsoidal form) H M E HMEMercury lamp (reflector form) H M R HMRMetal halide lamp (ellipsoidal form) H I E HIEMetal halide lamp (reflector form) H I R HIRMetal halide lamp (tubular form) H I T HITHigh-pressure sodium lamp (ellipsoidal form) H S E HSEHigh-pressure sodium lamp (tubular form) H S T HSTFluorescent lamp (L) (M) T TCompact fluorescent lamp (L) (M) TC TCLow-pressure sodium lamp L S T LST

Halogen lamp, double-ended QT-DEHalogen reflector lamp, coolbeam, without cover QR-CBHalogen reflector lamp, coolbeam, with cover QR-CBCMetal halide lamp, double-ended HIT-DECompact fluorescent lamp TC– without starter for EB TC-EL– with 4 discharge tubes TC-D– with 4 discharge tubes, with integral EB TC-DSE– with 4 discharge tubes, without starter for EB TC-DEL– linear form TC-L

G GlassQ Quartz glassM MercuryI Metal halideS Sodium vapour

A GeneralE EllipsoidalPAR Parabolic reflectorR ReflectorT TubularTC Compact tubes

The ZVEI, the German Electrical Engineeringand Industrial Federation, has developed a system of abbreviations for electric lampsused for general lighting purposes.Some lamp do manufacturers use differentabbreviations, however.

The ZVEI system of designation consistsof up to three characters. These aresupplemented by further abbreviations forspecial models or versions, which arehyphenated.

Standard abbreviationsfor lamps in this book.The letters in bracketsare not used in practice.The resulting abbrevia-tions are given in theright-hand column.

Abbreviations for special models or ver-sions are separatedfrom the main abbre-viation by a hyphen.

The first letter indicatesthe light production.

The second letter indi-cates the material ofthe outer envelope forincandescent lamps, or the gas contained indischarge lamps.

The third letter orcombination of lettersindicates the form of the outer envelope.

To complete the classi-fication of a lamp dataregarding diameter oflamp or reflector, power,colour of outer enve-lope, beam spread, typeof cap and voltage canbe added to the aboveidentification.

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5.0 AppendixGlossary

Glossary AberrationDefective image in the eye. A distinction ismade between spherical aberration, whichis a result of the different focal lengths of central and peripheral areas of the lens,and chromatic aberration, which occurswhen the refraction of light of differentwavelengths is changed

Absorption The ability of materials and substances totransform light into other forms of energy(primarily heat) without reflecting ortransmitting it. The degree of absorption isdefined as the ratio of absorbed luminousflux to the incident flux

Accent lightingAccenting of individual areas of a spaceby means of lighting that is significantlyhigher than the level of → the ambientlighting. → Focal glow

AccommodationThe physiological adjustment of the eye tobe able to identify objects at differentdistances. Effected by deformation of thelens. Accommodation deteriorates withage

AdaptationThe ability of the eye to adjust to → lumi-nances in the field of vision. Effected pri-marily through the enlarging or reducing ofthe size of the pupil, most significantlyeffected by changes in the sensitivity of thereceptors on the retina and the changebetween → photopic vision and → scotopicvision

Ambient lightAmbient light provides general lighting of the visual environment. Architecture,objects and people in the environmentare visible, which allows orientation, workand communication

Angle of viewAngle at which an object under view is perceived, measure for the size of theimage of the object on the → retina

AnodizingElectro-chemical oxidation of metalsurfaces, mostly of aluminium. Anodizedsurfaces that are subsequently polished or treated chemically to produce a glossy finish are extremely durable and havehigh → (luminous) reflectance

BallastCurrent limiting → control gear for → discharge lamps. Current limitation iseffected either inductively, using a choke,or electronically. Inductive ballasts areavailable as conventional ballasts (CB) orlow-loss ballasts (LLB). They may requirean additional ignitor or starting device.Electronic ballasts (EB) do not require additional ignitors. They do not producedisturbing humming noises or → strobscopic effects

BarndoorsTerm used to describe rectangular anti-dazzle screens used predominantly withstage projectors

Batwing characteristics→ Light intensity distribution curve of aluminaire with especially wide-angledlight intensity distribution characteristics.The name is derived from the batwingshape of the light intensity distributioncurve

Beam spreadThe angle between the limits from whichthe axial value of a → light intensitydistribution curve decreases to 50%. Thebeam spread is the basis for calculatingthe diameter of light beams emitted bysymmetrical luminaires

Biological needs The biological needs a lighting concept is expected to meet depend largely on thespecific activities to be performed.They are the result of basic human needsfor information regarding the time of day, the weather and things that are hap-pening. This fulfils the need for safety,spatial orientation and a clearly structured,legible environment together with theneed for a balanced ratio of possiblecontact with other persons and a privatedomain

Black body→ Planckian radiator

BrillianceDescribes the effect of light on glossysurfaces or transparent materials. Brillianceis produced by the reflection of the lightsource or the light being refracted; it isproduced by compact, point light sources

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CandelaRepresented by the symbol l (cd)Unit of → luminous intensity, the basicunit of measure in lighting technology. 1 cd is defined as the luminous intensityemitted by a monochromatic light sourcewith a radiant power of 1/683 W at 555 nmat a solid angle of 1 steradian

Capacitive circuitsCircuits where a discharge lamp run on aninductive → ballast (CB, LLB) is compen-sated using a series capacitor. The circuit isthen over-compensated, which meansthat a second lamp can be operated inparallel with the first (→ lead-lag circuit)

CBAbbreviation for conventional → ballast

Central field of visionThe central field of vision is effectivelythe same as the working plane, as itconsists of the visual task and its directambient field. The central field of vision is enclosed by the surrounding field as anextended ambient field. The concepts of central field of vision and surroundingfield are used mainly in connectionwith luminance distribution

Chromacity coordinates→ Standard colorimetric system

Chromacity diagram→ Standard colorimetric system

Chromatic aberration→ Aberration

CIEAbbreviation for Commission Internationalede l'Eclairage, international lighting com-mission

Colour adaptationThe ability of the eye to adjust to the → luminous colour of an environment.Allows relatively natural colour perceptioneven amongst different luminous colours

Colour renderingQuality of the reproduction of coloursunder a given light. The degree of colour distortion in comparison with a referencelight source is classified by the colourrendering index Ra, or by the colour ren-dering category

Colour temperatureDescribes the → luminous colour of alight source. In the case of thermal radia-tors the colour temperature is almostequivalent to the temperature of the fila-ment. In the case of discharge lamps, acorrelated colour temperature is given.This is the temperature at which a→ black body emits light of a comparablecolour

Compact fluorescent lamp→ Fluorescent lamps with especiallycompact dimensions due to a combinationof several short discharge tubes or one curved discharge tube. Compact fluorescentlamps are single-ended lamps; starters,and sometimes also → ballasts, can be in-tegrated into the cap

CompensationIf → discharge lamps are run on inductive→ ballasts (CB, LLB), the power factoris below unity. Due to the phase shift ofthe voltage with respect to the current acertain amount of blind (reactive, wattless)current is produced, which loads thepower mains. In the case of large-scaleinstallations power supply companiesrequire the blind current to be compensatedby means of power factor correction capacitors

Cone vision→ Photopic vision

Cones→ Eye

ConstancyThe ability of human perception to distin-guish the constant qualities of objects(size, form, reflectance/colour) from changesin the environment (changes in distance,position within the space, lighting). Thephenomenon of constancy is one ofthe essential prerequisites that allow thecreation of a clearly structured image of reality from the changing luminancepatterns on the retina

ContrastDifference in the → luminance or colourof two objects or one object and itssurroundings. The lower the contrast level,the more difficult the → visual task

Contrast renditionCriterion for limiting reflected glare.Contrast rendition is described by the con-trast rendition factor (CRF), which isdefined as the ratio of the luminance con-trast of the visual task under givenlighting conditions to the luminance con-trast under reference lighting conditions

Control gearControl gear is the equipment required inaddition to the actual lamp for the opera-tion of the light source. This comprisesgenerally → ballasts that regulate thecurrent flow, → ignitors and → startingdevices for the operation of dischargelamps, and transformers for the operationof low-voltage lamps

Controlling brightness → Dimmer

ConvergenceAlignment of the optical axes of the eyesto an object, effectively parallel in thecase of objects viewed at a considerabledistance, meeting at an angle in the caseof objects viewed at close range

Coolbeam reflector→ Dichroic reflector which reflects mainlyvisible light but transmits (glass reflec-tors) or absorbs (metal reflectors) infraredradiation. Using coolbeam reflectorsreduces the thermal load on illuminatedobjects. Often referred to as multi-mirrorreflectors

CoveArchitectural element on the ceiling or wall that can accommodate luminaires(usually → fluorescent lamps or → high-voltage fluorescent tubes) for indirectlighting

Cove reflectorReflector for linear light sources, by whichthe cross section at right angles to thelongitudinal axis determines the lightingeffect

Cut-off angle (lamp)Angle above which no direct → reflectionfrom the light source is visible in the → reflector. In the case of → darklight re-flectors the cut-off angle of the lamp isidentical to the cut-off angle of the lumi-naire. In other forms of reflector it maybe less, so that reflected glare occurs in thereflector above the cut-off angle

Cut-off angle (luminaire)The angle taken from the horizontal to theline from the inner edge of the luminaireto the edge of the light source. Togetherwith the → cut-off angle (lamp), thisangle is used to identify the glare limitationof a luminaire

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Darklight reflector→ Reflector

DaylightDaylight consists of both direct sunlightand the diffuse light of an overcast orclear sky. Daylight illuminances are signi-ficantly higher than the illuminancesproduced by artificial lighting. The→ lumi-nous colour is always in the → daylightwhite range

Daylight factorRatio of the → daylight → illuminance on the → working plane in a space to theoutdoor illuminance

Daylight simulatorTechnical equipment for simulating sun-light and → daylight. Daylight is eithersimulated by a semi-spherical shaped ar-rangement of numerous luminaires or by the multireflection of a laylight ceilingin a mirrored room. Sunlight is simulatedby a parabolic spotlight, which is moved tocoordinate with the course of the sunfor the duration of one day or one year. Adaylight simulator allows model simula-tions of light and shadow conditions in planned buildings, the testing of lightcontrol equipment and measurement of→ daylight factors on the model

Daylight white, dw→ Luminous colour

Daytime vision→ Photopic vision

Dichroic filters→ Filters

Dichroic reflectorReflector with a multi-layered selectivereflective coating, which only reflects apart of the spectrum and transmits others.Dichroic reflectors are used primarily as → coolbeam reflectors, reflecting visiblelight and transmitting→ infrared radiation.They are also used for inverse effect outerenvelopes on lamps to increase thetemperature of the lamp (hot mirror)

Diffuse lightDiffuse light is emitted by large luminousareas. The result is uniform, soft lightingwhich produces little → modelling or → brilliance

DimmerRegulating device for varying the lumi-nous intensity of a light source. Generallyin the form of a loss-free leading edgedimmer. Conventional dimmers can be usedwithout problems for incandescent lampsrun on mains voltage. Dimmers for fluore-scent lamps and low-voltage lamps aretechnically more complicated; the dimmingof high-pressure discharge lamps is tech-nically possible, but it is also costly and isnot often provided

Direct glare→ Glare

Directed lightDirected light is emitted by point lightsources. The beam direction is from oneangle only, which provides→ modelling and→ brilliance effects. Exposed lamps alsoproduce directed light. The variable beamdirections within the space are generallyaligned to produce uniformly directedbeams of light. → Controlling light.

Disability glare→ Glare

Discharge lampLight source that produces light by excitinggases or metal vapours. The qualities ofthe lamp depend on the contents of thedischarge tube and the operating pressureof the lamp. A distinction is thereforemade between high-pressure and low-pressure discharge lamps. Low-pressuredischarge lamps have a larger lamp volumeand correspondingly low lamp lumi-nances. The light emitted comprises onlynarrow spectral ranges, which to a largeextent restricts colour rendition characte-ristic. Colour rendering can be improvedsubstantially by adding luminous sub-stances. High-pressure discharge lampshave a small lamp volume and havecorrespondingly high luminance values.The high operating pressure leads to the broadening of the spectral ranges pro-duced, which in turn leads to improved → colour rendition. Increasing the lamppressure frequently also means an increasein luminous efficacy

Discomfort glare→ Glare

Distribution characteristics→ luminous intensity distribution curve

Double focus reflector→ Reflector

EBAbbreviation for electronic → ballast

Elliptical reflector→ Reflector

EmitterMaterial that facilitates the transfer ofelectrons to be converted from the elec-trodes into the discharge column of thelamp. To allow ignition to occur the elec-trodes in a large number of dischargelamps are coated with a special emittermaterial (usually barium oxide)

ExposureRepresented by the symbol H (lx.h)Exposure is defined as the product of theilluminance and the exposure timethrough which a surface is illuminated

EyeThe eye consists of an optical system,comprising the cornea and the deformablelens which enable images of the environ-ment to be reproduced on the retina. Byadjusting the size of the aperture of thepupil the iris roughly controls the amountof incident light. The pattern of lumi-nances on the retina is translated into ner-vous impulses by receptor cells. There are two kinds of receptor in the eye: therods and the cones. The rods are distri-buted fairly evenly over the retina, they areextremely sensitive to light and allowwide-angled vision at low illuminances(→ scotopic vision). Visual accuity is poor,however, and colours are not perceived.The cones are concentrated in the centralarea around the fovea, which is locatedon the axis of sight. They allow colours andsharper contours to be seen in a narrowangle of vision, but require high illumi-nances (→ photopic vision)

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5.0 AppendixGlossary

FilterOptically effective element with selective→ transmission. Only a part of the radia-tion falling on a surface is transmitted, sothat either coloured light is produced orinvisible portions of radiation (→ ultra-violet, → infrared) are eliminated. Filtereffects can be achieved by means of selective → absorption or → interference.Interference filters allow an especiallyclear division of the light that is transmit-ted and that which is eliminated by thefilters

FloodUsual term used for wide-beam → reflec-tors or → reflector lamps

FluorescenceFluorescence is a process by which sub-stances are excited by means of radiationand made to produce light. The wavelengthof the light emitted is always greaterthan the wavelength of the radiation usedto excite the substances. Fluorescence isused in technical applications for → lumi-nous substances that convert → ultra-violet radiation into visible light

Fluorescent lampLow-pressure → discharge lamp filled withmercury vapour. The ultraviolet radiationproduced during the mercury dischargeprocess is converted into visible lightby the luminous substances on the innerwall of the discharge tube. By usingdifferent luminous substances it is possibleto produce a variety of luminous coloursand different colour rendering qualities.As a rule, fluorescent lamps have heatedelectrodes and can therefore be ignited atcomparatively low voltages. Fluorescentlamps require an ignitor and a ballast,→ EB

Focal glowFocal glow refers to accent lighting. Light is used deliberately to convey informationby visually accentuating significant areasand allowing insignificant areas to remainin the background

Fovea→ Eye

Fresnel lensStepped lens, where the effect of a consi-derably thicker lens is achieved by a flat arrangement of lens segments. Opticaldisturbance caused by the edges of theprisms is usually corrected by producing agrained finish on the rear side of the lens.Fresnel lenses are primarily used in stageprojectors and spotlights with adjustable→ beam spreads

Functional requirements (Lam: activity needs)The functional requirements a lightingconcept is expected to meet are dictated bythe visual tasks which are to be perfor-med; the aim is to create optimum percep-tual conditions for all activities to beperformed in a specific area

Gas lightAn early form of lighting using a bare gasflame to produce light

General lightingUniform lighting of an entire space with-out taking specific visual tasks into account.→ Ambient lighting

General service lamp→ Incandescent lamp

Gestalt (form) perceptionTheory of perception that presumes thatperceived structures are regarded asa gestalt, i.e. as complete forms, and notsynthesized as individual elements. Eachgestalt is classified according to a specificlaw of gestalt and separated from itsenvironment

GlareGeneric term describing the depreciationof → visual performance or the distur-bance felt by perceivers through excessive→ luminance levels or → luminancecontrasts in a visual environment. A distinc-tion is made between disability glare,which does not depend on luminance con-trast, and contrast-related relative glare.Furthermore, a distinction is made betweendisability glare (physiological glare), bywhich there is an objective depreciation ofvisual performance, and discomfort glare,which involves a subjective disturbancefactor arising from the incongruity of lumi-nance and information content of thearea perceived. In all cases glare canbe caused by the light source itself (directglare) or through the reflection of thelight source (reflected glare)

GoboTerm used in stage lighting to describe amask or template, which can be projectedonto the set using a projector

Goniophotometer→ Photometer

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276

Halogen lampCompact incandescent lamp with additio-nal halides in the gas compound, whichprevents deposits of the evaporated fila-ment material forming on the outerenvelope. In contrast to general servicelamps, halogen lamps have increasedluminous efficacy and a longer service life

High-pressure discharge lamps→ Discharge lamps

High-pressure mercury lampHigh-pressure→ discharge lamp containingmercury vapour. In contrast to the low-pressure discharge process, which producesalmost exclusively → ultraviolet radiation,at high pressure mercury vapour producesvisible light with a low red content. Lu-minous substances can be added to com-plement the red content and improve → colour rendering. High-pressure mercurylamps require → ballasts, but no→ ignitors

High-pressure sodium lampHigh-pressure discharge lamp containingsodium vapour. As aggressive sodiumvapour can destroy glass at high pressures,the internal discharge tube is madeof alumina ceramic and surrounded by anadditional outer envelope. In contrast to → low-pressure sodium lamps colourrendition is considerably improved, but at the expense of luminous efficacy. Theluminous colour is in the warm whiterange. High-pressure sodium lamps require→ ignitors and → ballasts

High-voltage fluorescent tubes→ Fluorescent lamps similar to low-pressure→ discharge lamps, which work withunheated electrodes and accordingly requirehigh voltages. The discharge tubes can be extremely long and have a variety offorms. They are used primarily for luminous advertising and for theatricaleffect. They are filled with neon or argongas and contain luminous substances,which can produce a large number ofluminous colours. High-voltage fluorescenttubes require an→ ignitor and a → ballast

Ignition aidEquipment to facilitate ignition, e.g. inthe case of → fluorescent lamps withunheated electrodes, usually an auxiliaryelectrode or an external ignitor system

Ignitor→ Control gear which promotes the igni-tion of → discharge lamps by producinghigh-voltage peaks. Leakage transformers,ignition transformers, ignition pulsers andelectronic ignitors can be used as ignitors

IlluminanceRepresented by the symbol E (lx)Illuminance is defined as the ratio of theamount of luminous flux falling on a sur-face to the area of the surface

Incandescent gas lightForm of lighting whereby an incande-scent mantle coated with rare earths, ori-ginally using other solid bodies (e.g.limestone, limelight) is excited to thermo-lumine-scence using a gas flame. Theluminous efficacy is far greater and thelight produced of a shorter wavelengththan is the case with pure → gas light

Incandescent lamp→ Thermal radiator, where light is produ-ced by the heating of a wire filament(usually tungsten). The filament is contai-ned in an outer envelope made of glassand filled with a special gas (nitrogen orinert gas) to prevent the filament fromoxidizing and to slow down the vaporisa-tion of the filament material. There arevarious types of incandescent lamps avai-lable: the main group comprises generalpurpose lamps with drop-shaped, clear orfrosted outer envelopes, the reflectorlamp with a variety of internal mirrors, andthe PAR lamp made of pressed glass withan integral parabolic reflector

Inductive circuitsCircuit in which a non-compensated dis-charge lamp can be operated on aninductive → ballast (CCB, → LLB). In thiscase the power factor of the installationis below unity

Infrared radiationInvisible long-wave radiation (thermalradiation, wavelength >780 nm). Infraredradiation is produced by all light sources,especially thermal radiators, where it is themajor component of the emitted ra-diation. At high illuminance levels infraredradiation can lead to inacceptable thermalloads and damage to materials

InterferencePhysical phenomenon which occurs whenasynchronous waves are superimposed,which results in the selective attenuationof wavelength ranges. Interference is usedin → filters and → reflectors for selective→ transmission or → reflection

Interference filters→ Filters

Inverse square lawLaw that describes the → illuminance asthe function of the distance from thelight source. The illuminance decreaseswith the square of the distance

Involute reflector→ Reflector

Isoluminance diagramDiagram to illustrate luminance distribu-tion, in which lines representing values ofluminance are indicated on a referenceplane

Isolux diagramDiagram to illustrate illuminance distribu-tion, in which lines representing values of illuminance are indicated on a referenceplane

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277

Lambertian radiatorCompletely diffuse light source, whose → luminous intensity distribution (withregard to the cosine law) is the shape of a sphere or a circle

LDCAbbreviation for → light distributioncurve

Leading edge dimmingMethod of controlling the brightness, inwhich the power to the lamps is controlledby cutting out the leading edge of wavesof alternating current

Lead-lag cicuitWiring of an inductive → fluorescentlamp in parallel with an over-compensatedfluorescent lamp. The power factor of the overall circuit is effectively unity. Sinceboth lamps are out-of-phase, there isless fluctuation of luminous intensity

Light controlThe control of light using reflectors orlenses is used to develop luminaires withclearly defined optical qualities as in-struments for effective lighting design.Different luminaire types allow lightingeffects ranging from uniform lighting to theaccentuation of specific areas to theprojection of light patterns. Light controlis extremely significant for → visualcomfort. With the aid of light control the→ luminance that can give rise to glare in the critical beam area can be reduced toan acceptable level

Light fastnessIs an indication of the degree by which amaterial wll be damaged by the effect of light. Light fastness applies primarily tochanges in the colour of the material(colour fastness), but may also apply tothe material itself

Light loss factorFactor (usually 0.8), which is included inilluminance calculations, e.g.when using theutilisation factor method, to take intoaccount the reduction in performance ofa lighting installation due to the ageingof the lamps and the deterioration of thelight output from the luminaires

Light output ratio→ Luminaire light output ratio

Lighting controlLighting control allows the lighting of a space to be adjusted to meet changinguses and environmental conditions. Alight scene is created for each differentuse , i.e. a specific pattern of switchingand dimming for each circuit. The lightscene can be stored electronically andrecalled at the touch of button

Line spectrum→ Spectrum

LitG→ Abbreviation for Lichttechnische Gesell-schaft e.V. (German Lighting EngineeringSociety)

LLB→ Abbreviation for low-loss → ballast

Louvred luminaireStandard term used to describe rectangularluminaires designed for linear fluorescentlamps (modular luminaires), frequentlyequipped with specular, prismatic or anti-dazzle louvres

Low-pressure discharge lamp→ Discharge lamp

Low-pressure sodium lampLow-pressure discharge lamp containingsodium vapour. The internal dischargetube is surrounded by an outer envelopethat reflects infrared radiation to increasethe lamp temperature. Low-pressuresodium lamps have excellent luminousefficacy. As they emit monochromatic,yellow light, it is not possible to recognisecolours under the lighting provided bythese lamps. Low-pressure sodium lampsrequire → ignitors and → ballasts

Low-voltage halogen lampExtremely compact → tungsten halogenlamps operated on low voltage (usually 6,12, 24 V). Frequently also available withmetal reflectors or → coolbeam reflectors

Lumen, lm→ Luminous flux

Luminaire classificationSystem for the classification of luminairequalities according to the luminousintensity distribution curve. In the classifi-cation of the luminous intensity of aluminaire through the allocation of a letterand digits, the letter indicates the lumi-naire category, i.e. defines whether a lumi-naire emits light upwards or downwards.The first digit after that describes theportion of direct luminous flux falling onthe working plane in the lower half of the room, and the second digit indicates thecorresponding value for the upper half of the room

Luminaire efficiencyLuminaire light output ratio

Luminaire light output ratioRatio of the luminous flux emitted by aluminaire to the luminous flux of thelamp. The luminaire light output ratio isrelated to the actual lamp lumens in the luminaire

LuminanceRepresented by the symbol L (cd/m2)Luminance describes the brightness of aluminous surface which either emits lightthrough autoluminance (as a lightsource), → transmission or → reflection.The luminance is accordingly defined as the ratio of → luminous intensity to thearea on a plane at right angles to the direction of beam

Luminance limiting curve→ Luminance limiting method

Luminance limiting methodMethod for evaluating the potential glare of a luminaire. The luminance of theluminaire with different beam spreads is entered in a diagram, in which the lumi-nance curve must not exceed the lumi-nance limit for the required glare limitationclassification

LuminescenceGeneral term for all luminous pheno-mena that are not produced by thermalradiators (photoluminescence, chemo-luminescence, bioluminescence, electro-luminescence, cathodoluminescence,thermal luminescence, triboluminescence)

Luminous colourThe colour of the light emitted by a lamp.The luminous colour can be identified by x, y coordinates as chromacity coordinatesin the → standard colorimetric system, in the case of white luminous colours alsoas a colour temperature TF. White lumi-nous colours are roughly divided up intowarm white (ww), neutral white (nw) anddaylight white (dw). The same luminouscolours may have different spectral distri-butions and correspondingly different → colour rendering

Luminous efficacyLuminous efficacy describes the luminousflux of a lamp in relation to its powerconsumption, (lm/W)

Luminous fluxRepresented by the symbol Ï (lm)Luminous flux describes the total amountof light emitted by a light source. It iscalculated from the spectral radiant powerby the evaluation with the spectralsensitivity of the eye V (¬)

Luminous intensityRepresented by the symbol l (cd)Luminous intensity is the amount of lumi-nous flux radiating in a given direction(lm/sr). It describes the spatial distributionof the luminous flux

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Luminous intensity distribution curveThe luminous intensity distribution curve,or light distribution curve, is the sectionthrough the three-dimensional graphwhich represents the distribution of theluminous intensity of a light sourcethroughout a space. In the case of rota-tionally symmetrical light sources onlyone light distribution curve is required.Axially symmetrical light sources requiretwo or more curves. The light distributioncurve is generally given in the form of a polar coordinate diagram standardisedto a luminous flux of 1000 lm. The polarcoordinate diagram is not sufficiently ac-curate for narrow-beam luminaires, e.g. projectors. In this case it is usual toprovide a Cartesian coordinate system

Lux, lx→ Illuminance

Maintenance factorReciprocal value of the → light loss factor

Mesopic visionTransitional stage between → photopicvision, i.e. daylight vision with the aid of→ cones and scotopic vision, i. e. night vision with the aid of → rods. Colour per-ception and visual accuity have corre-sponding interim values. Mesopic visioncovers the luminance range of 3 cd/m2

to 0.01 cd/m2

Metal halide lamp→ High-pressure discharge lamp wherethe envelope is filled with metal halides.In contrast to pure metals, halogen com-pounds melt at a considerably lower tem-perature. This means that metals that donot produce metal vapour when the lampis in operation can also be used. The avai-lability of a large variety of source materialsmeans that metal vapour compoundscan be produced which in turn produce highluminous efficacy during the dischargeprocess, and good colour rendering

Mode of ProtectionClassification of luminaires with regard to the degree of protection providedagainst physical contact and the ingressof foreign bodies or water

ModellingAccentuation of three-dimensional formsand surface structures through directlight from point light sources. Can be ex-plained by the term→ shadow formation

Modular luminairesGeneral term used to describe rectangularluminaires designed to take tubularfluorescent lamps. As → louvred luminairesfrequently equipped with specular, pris-matic or anti-dazzle louvres

Monochromatic lightLight of one colour with a very narrowspectral range. Visual accuity increasesunder monochromatic light due to the fact that chromatic → aberration doesnot arise. Colour rendition is not possible

Multi-mirror→ Coolbeam reflector

Neutral white, nw→ Luminous colour

Night vision→ Scotopic vision

Optical fibres, fibre optic systemOptical instrument for conveying light torequired positions, including around cor-ners and bends. Light is transported fromone end of the light guide to the other by means of total internal reflection. Lightguides are made of glass or plastic andmay be solid core or hollow fibres

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PAR lamp→ Incandescent lamp

Parabolic reflector→ Reflector

Perceptual physiologyField of science concerning the biologicalaspects of perception, especially the waythe brain receives and processes sensestimuli

Perceptual psychologyField of science concerning the mentaland intellectual aspects of perception, especially the way received sense stimuliare processed

Permanent supplementary artificiallighting, PSALIAdditional artificial lighting, especially indeep office spaces with a row of windowsalong one side of the space only. Permanentsupplementary artificial lighting balancesthe steep drop in illuminance in parts of thespace furthest away from the windowsand contributes towards avoiding → glareby reducing the luminance contrast be-tween the windows and the surroundingspace

PhotometerInstrument for measuring photometricquantities. The primary quantity measuredis → illuminance, from which otherphotometric quantities are derived. Photo-meters are adjusted to the spectralsensitivity of the eye (V(¬) adjustment). Special, large-dimensioned photometricequipment (goniophotometers) is requiredfor measuring the light distribution ofluminaires. Measurement is carried out bymoving the measuring device around the luminaire (spiral photometer) or bydirecting the luminous flux onto a stationarymeasuring device via an adjustable mirror

Photometric distance of toleranceMinimum distance above which the influ-ence of the size of the lamp or luminaireon the validity of the inverse square law canbe ignored. The photometric distance oftolerance must be at least ten times themaximum diameter of the lamp or lumi-naire; in the case of optical systems thephotometric distance of tolerance is esta-blished by experimentation

Photopic vision(Daylight vision). Vision with → adaptationto luminances of over 3 cd/m2. Photo-metric vision occurs through the → conesand is therefore concentrated on the area around the → fovea. → Visual accuityis good. Colours can be perceived

Planckian radiator(Black body). Ideal thermal radiator whose radiation properties are describedin the Planck's Law

Play of brilliancePlay of brilliance is the decorative appli-cation of light. Specular effects producedby light source and illuminated materials – from the candle flame to the chandelierto the light sculpture – contribute to-wards creating a prestigious, festive orexciting atmosphere

Point illuminance In contrast to average illuminance, whichexpresses the average level of illuminancein a space, point illuminance describesthe exact level of illuminance at a specificpoint in the space

Point light sourceTerm used to describe compact, practicallypoint-sized light source emitting directlight. Point light sources allow optimumcontrol of the light, especially the bundlingof light, whereas linear or flat lightsources produce diffuse light, which in-creases with size

Power factor→ Compensation

Prismatic louvreElement used for controlling light inluminaires or for controlling daylight usingrefraction and total internal reflection inprismatic elements

Protection classClassification of luminaires with regard to the rate of protection provided against electric shock

Reflected ceiling planThe view of a ceiling plan from above, pro-vided to show the type and arrangementof the luminaires and equipment to be in-stalled

Reflected glare→ Glare

ReflectionAbility of materials to redirect light. Thedegree of reflection is expressed in thereflection factor (reflecting coefficient). It indicates the ratio of the reflected lumi-nous flux to the luminous flux falling on a surface

ReflectorSystem for controlling light based onreflecting surfaces. The characteristics of areflector are primarily the reflecting anddiffusing qualities, and in the case of mir-ror reflectors the contours of the crosssection. Parabolic reflectors direct the lightfrom a (point) light source parallel tothe axis, spherical reflectors direct the lightback to the focal point and ellipticalreflectors direct the light radiated by a lamplocated at the first focal point of theellipse to the second focal point

Reflector lamp→ Incandescent lamp

RefractionThe bending of rays of light as they pass through materials of different density.The refracting power of a medium isdefined as the refractive index

Refraction of lightBending of rays of light as they pass throughmaterials of different density. The refrac-tion of different parts of the spectrum todifferent degrees gives rise to the forma-tion of colour spectra (prisms).

Re-ignitionThe restarting of a lamp after it has beenswitched off or after current failure. A large number of → discharge lamps canonly be re-ignited after a given coolingtime. Instant re-ignition is only possiblewith the aid of special high-voltage → ignitors

Relative glare→ Glare

Requirements, architecturalThe architectural requirements a lightingconcept is expected to meet are dictatedby the structure of the architecture. Thetask of the lighting is to reinforce the waythe space is divided up, its forms, rhythmsand modules, to emphasise architecturalfeatures and support the intended atmos-phere of the building. The intention ofthe architectural design can be underlined,and even enhanced, through the arrange-ment and effects of the luminaires

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Retina→ Eye

Retro-reflectionReflection in rectangular reflector systems(triple mirrors) or transparent spheres, bywhich the light is reflected parallel to theincident light

Rods→ Eye

Room indexWhen calculating → illuminances usingthe → utilisation factor method, the roomindex indicates the geometry of the space

ScallopHyperbolic beam shape of a beam of light.Scallops are produced by grazing walllighting from downlights

Scotopic vision(Night vision). Vision with → adaptationto luminances of less than 0.01 cd/m2.Scotopic vision is effected with the aidof the → rods and comprises the peripheralarea of the → retina. → Visual accuityis poor, colours cannot be perceived, sen-sitivity to the movement of perceivedobjects is high

Secondary reflector technologyLuminaire technolgy where an indirect or a direct/indirect component is not pro-duced by lighting the room surfaces,but by the use of the luminaire's own secon-dary reflector. Secondary reflector lumi-naires frequently have a combination ofprimary and secondary reflectors, whichallows good control of the direct and in-direct → luminous flux emitted

Self ballasted mercury discharge lamp,blended lamp→ High-pressure mercury lamp with an additional filament within the outer en-velope which is connected in series andtakes the form of a current limiter, whichresults in improved colour rendition. Selfballasted mercury discharge lamps need no→ ignitor or → ballast, as the namesuggests

Shadow formationMeasure for the → modelling quality of a lighting installation. Modelling can bedescribed as the ratio of the averagevertical (cylindrical) illuminance to the ho-rizontal → illuminance at a given point in the space

Solid angleRepresented by the symbol ØUnit for measuring the angular extent of an area. The solid angle is the ratio ofthe area on a sphere to the square of the sphere's radius

SpectrumDistribution of the radiant power of alight source over all wavelengths. The→ spectral distribution gives rise to the→ luminous colour and → colour ren-dering. Depending on the type of lightproduced, basic types of spectra candiffer: the continuous spectrum (daylightand → thermal radiators), the line spec-trum (low-pressure discharge) and bandspectrum (high-pressure discharge)

Specular louvres→ Reflector

Spherical aberration→ Aberration

Spherical reflector→ Reflector

Spiral photometer→ Photometer

SpotGeneral term used to describe narrow-beam → reflectors or → reflector lamps

Standard colorimetric systemSystem for defining luminous colours andbody colours numerically. The standardcolorimetric system is presented in a two-dimensional diagram in which the colourloci of all colours and colour blends fromtheir purely saturated state to white are numerically described through their x,ycoordinates → chromaticity diagram.Combinations of two colours lie along thestraight lines that link the respectivecolour loci. The luminous colour of thermalradiators is located on the curve of thePlanckian radiator

StarterIngnition device for → fluorescent lamps.When the lamp is switched on the lampthe starter closes a preheat circuit, whichin turn heats the lamp electrodes. After a specific preheating time the electric cir-cuit is opened, which through inductionproduces the voltage surge in the → ballastrequired to ignite the lamp

Stepped lens→ Fresnel lens

Steradiant, sr→ Solid angle

Stroboscopic effectsFlickering effects or apparent changes inspeed of moving objects due to pulsatinglight (through the supply frequency) upto apparent standstill or a change of direc-tion. Stroboscopic effects can arise in → discharge lamps, predominantly in dim-med fluorescent lamps. They are distur-bing and dangerous in spaces where peopleare operating machines. The effect can be counteracted by operating the lamps outof phase (→ lead-lag circuit, connectionto three-phase mains) or on high-frequencyelectronic → ballasts

Sun simulator→ Daylight simulator

Sunlight→ Daylight

Surrounding field→ Central field of vision

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Tandem circuitOperation of two → fluorescent lampsswitched in series on one → ballast

Task lightingUsed generally to describe the illuminationof workplaces in accordance withgiven standards and regulations. Additionallighting of the workplace which goesbeyond → general lighting to meet thedemands of specific visual tasks

Thermal radiatorRadiant source which emits light throughthe heating of a material. An ideal → Planckian radiator emits a spectrumpursuant to the Planck's Law; in the case of materials used in practice (e. g.tungsten in wire filaments) the spectrumproduced differs slightly from thisspectral distribution

Thermoluminescence→ Luminescence

Transformer→ Control gear

TransmissionAbility of materials to allow light to passthrough them. This ability is expressed as a transmission factor, which is definedas the ratio of transmitted luminous flux to the luminous flux falling on a sur-face

Tri-phosphor lamp→ Fluorescent lamp

Ultraviolet radiationInvisible radiation below short-wave light(wavelength <380 nm). Light sourcesused for architectural lighting only emit asmall portion of ultraviolet radiation.Special light sources designed to producea higher portion of ultraviolet radiationare used for medical and cosmetic purposes(disinfection, tan effect) and in photo-chemistry. Ultraviolet radiation can have adamaging effect: colours fade and mate-rials become brittle.

UtilanceUtilance is the ratio of the→ luminous fluxfalling on the working plane to the lumi-nous flux emitted by a luminaire. It is theresult of the correlation of room geo-metry, the reflectance of the room surfacesand the luminaire characteristics

Utilisation factor methodMethod for calculating the average → illuminance of spaces with the aid ofthe → light output ratio, the → utilanceand the lamp lumens

VDT-approved luminaireLuminaires designed for application inoffices equipped with visual display termi-nals

Visual accuityAbility of the eye to perceive details. The unit of measure is the visus, which isdefined as the reciprocal value of the sizeof the smallest detail that can be perceived(usually the position of the opening inthe Landolt broken ring) in minutes of arc

Visual comfortVisual comfort is generally understood as the quality of a lighting installation thatmeets a number of quality criteria. (→ illuminance, → luminance ratios, → colour rendition, → modelling)

Visual taskExpression for the perceptual perfomancerequired of the eye or for the visualqualities of the object to be perceived. Thegrade of difficulty of a visual task growswith diminishing colour or luminancecontrast, and with the diminishing size ofdetails

Warm white, ww→ Luminous colourWorking planeStandardised plane to which illuminancesand luminances are related, usually 0.85 min the case of workplaces and 0.2 m incirculation zones

ZoningDividing up of the space into differentareas relating to their function

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Pritchard, D. C.: Lighting. Longman, London1978

Rebske, Ernst: Lampen, Laternen, Leuchten.Eine Historie der Beleuchtung. Franck,Stuttgart 1962

Reeb, O.: Grundlagen der Photometrie. G. Braun, Karlsruhe 1962

Riege, Joachim: Handbuch der lichttech-nischen Literatur. TU, Institut für Licht-technik, Berlin 1967

Ritter, Manfred (Einf.): Wahrnehmung und visuelles System. Spektrum der Wis-senschaft, Heidelberg 1986

Robbins, Claude L.: Daylighting. Designand Analysis. Van Nostrand Reinhold, New York 1986

Rock, Irvin: Wahrnehmung. Vom visuellenReiz zum Sehen und Erkennen. Spektrumder Wissenschaft, Heidelberg 1985

Rodman, H. E.: Models in ArchitecturalEducation and Practice. Lighting Design +Application 1973, June

SLG; LTAG; LiTG: Handbuch für Beleuch-tung. W. Giradet, Essen 1975

Santen, Christa van; Hansen, A. J.: Licht in de Architektuur – een beschouwing vordag- en kunstlicht. de Bussy, Amsterdam1985

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Schober, H; Rentschler, I.: Das Bild alsSchein der Wirklichkeit. Optische Täu-schungen in Wissenschaft und Kunst.Moos, München 1972

Sewig, Rudolf: Handbuch der Lichttechnik.Würzburg 1938, 2 Bände

Sieverts, E.: Bürohaus- und Verwaltungsbau.W. Kohlhammer GmbH, Stuttgart, Berlin,Köln, Mainz 1980

Sieverts, E.: Beleuchtung und Raumgestal-tung. In: Beleuchtung am Arbeitsplatz,BAU Tb49. Wirtschaftsverlag NW, Bremer-haven 1988

Söllner, G.: Ein einfaches System zur Blen-dungsbewertung. Lichttechnik 1965, Nr. 17

Sorcar, Parfulla C.: Rapid Lighting Designand Cost Estimating. McGraw-Hill, New York 1979

Sorcar, Praefulla C.: Energy Saving LightSystems. Van Nostrand Reinhold, New York1982

Spieser, Robert: Handbuch für Beleuch-tung. Zentrale für Lichtwirtschaft, Zürich1950

Steffy, Gary: Lighting for Architecture and People. Lighting Design + Application1986, July

Sturm, C. H.: Vorschaltgeräte und Schal-tungen für Niederspannungs-Entladungs-lampen. BBC, Mannheim, Essen

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Teichmüller, Joachim: Lichtarchitektur.Licht und Lampe, Union 1927, Heft 13, 14

Twarowski, Mieczyslaw: Sonne und Archi-tektur. Callwey, München 1962

Wahl, Karl: Lichttechnik. Fachbuchverlag,Leipzig 1954

Waldram, J. M.: The Lighting of GloucesterCathedral by the „Designed Appearence“Method. Transactions of the IlluminatingEngineering Society 1959, Vol. 24 No. 2

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Welter, Hans: Sportstättenbeleuchtung,Empfehlungen für die Projektierung undMessung der Beleuchtung. Lichttechnik1974, März, Vol. 26 No. 3

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5.0 AppendixAcknowledgements

AcknowledgementsGraphic material

Archiv für Kunst und Geschichte17 Shop window lighting using gas light

CAT Software GmbH165 Illuminance distribution165 Luminance distribution

Daidalos 27. Lichtarchitektur. March 198823 Wassili Luckhardt: Crystal on the

sphere23 Van Nelle tobacco factory, Rotterdam

Deutsches Museum, Munich20 Goebel lamps

ERCO24 Ambient light25 Focal glow25 Play of brilliance

Institut für Landes- und Stadtentwick-lungsforschung des Landes Nordrhein-Westfalen ILS (Hrsg.): Licht im Hoch- undStädtebau. Band 3.021. S. 17. Dortmund198013 The influence of light on northern and

southern architectural forms

Addison Kelly116 Richard Kelly

William M. C. Lam: Sunlighting asFormgiver for Architecture. New York(Van Nostrand Reinhold) 1986117 William Lam

Osram photo archives20 Heinrich Goebel

Correspondence Course Lighting Applica-tion. Vol. 2. History of Light and Lighting.Eindhoven 198413 Brass oil lamp15 Christiaan Huygens15 Isaac Newton17 Carl Auer v. Welsbach18 Jablochkoff arc lamps20 Joseph Wilson Swan20 Thomas Alva Edison21 Theatre foyer lit by Moore lamps23 Joachim Teichmüller

Henry Plummer: Poetics of Light.In: Architecture and Urbanism. 12. 198712 Sunlight architecture

Michael Raeburn (Hrsg.): Baukunst desAbendlandes. Eine kulturhistorische Doku-mentation über 2500 Jahre Architektur.Stuttgart 198212 Daylight architecture

Ernst Rebske: Lampen, Laternen, Leuchten.Eine Historie der Beleuchtung. Stuttgart(Franck) 196216 Lighthouse lighting using Fresnel

lenses and Argand burners17 Drummond’s limelight19 Siemens arc lamp, 186820 Swan lamp

Wolfgang Schivelbusch: Lichtblicke.Zur Geschichte der künstlichen Helligkeitim 19. Jhdt. München (Hanser) 198318 Arc lighting at the Place de la Concorde22 American lighthouse

Trilux: Lichter und Leuchter. Entwicklungs-geschichte eines alten Kulturgutes. Arns-berg 198714 Lamps and burners developed in the

2. half of the 19. century15 Paraffin lamp with Argand burner16 Fresnel lenses and Argand burner17 Incandescent mantle as invented by

Auer v. Welsbach18 Hugo Bremer’s arc lamp20 Edison lamps21 Low-pressure mercuy vapour lamp

developed Cooper-Hewitt

Ullstein Bilderdienst16 Augustin Jean Fresnel

Sigrid Wechssler-Kümmel: Schöne Lam-pen, Leuchter und Laternen. Heidelberg,München 196213 Greek oil lamp

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5.0 AppendixIndex

Index Index

Aberration 28, 57Absolute glare 79Absorption 87Accent lighting 53, 123, 126, 132, 136Accommodation 80Activity needs 112, 117, 118Adaptation 13, 38, 84Ambient light 24, 116Anodisation 88Architectural requirements 74, 119, 122

Ballast 52, 54–60, 61, 65–68, 71Batwing characteristics 89, 98Beam spread 41, 47, 77, 85, 91, 92, 98, 102Biological needs 74, 117, 118, 122Brilliance 47, 53, 78–80, 97, 114, 117, 126, 127

Candela, cd 41, 79, 99Capacitive circuit 67CB 65Chromacity coordinates 83Chromatic aberration 44, 57CIE 83Colour adaptation 84Colour temperature 47, 52, 54, 71, 78, 83, 84, 127, 128Colour rendition 22, 47, 49, 52, 54, 57–60, 83, 84, 111, 119, 126–128, 130Compact fluorescent lamp 25, 54, 55, 66, 72, 97, 102Compensation 67, 71Cones 37Constancy 31Contrast 39, 73, 79, 144Contrast rendering 81, 154, 158, 168Control gear 49, 65, 67, 85, 126Convergence 80Coolbeam reflector 47, 50, 88Cove reflector 89Cove 141Cut-off angle (lamp) 89, 94Cut-off angle (luminaire) 94, 99

Darklight reflector 90, 94Daylight 12, 15, 23, 31, 38, 47, 74, 76, 84, 122, 132, 150, 167, 168Daylight factor 167Daylight white 54, 60, 128Dichroic reflector 47, 49, 88Dichroic filters 88, 92Diffuse light 13, 53, 76, 85, 87, 88Dimmer 71, 73Direct glare 79-81, 98, 111, 137, 141, 143Direct field of vision 114Directed light 25, 76–78, 127, 137Disability glare 79Discharge lamp 21, 25, 43, 52, 53, 55, 60, 65, 68, 72, 83, 90, 101, 127, 128, 130, 132,

143Discomfort glare 79, 80Double-focus reflector 95

EB 65, 66Ellipsoidal reflector 90Emitter 53Exposure 24, 42Eye 12, 24, 28, 29, 37, 38, 43, 57, 75, 79, 83, 84, 112, 114, 115

Filter 53, 65, 87, 88, 92, 132Fluorescence 53Fluorescent lamp 21, 22, 25, 43, 53–55, 59, 65–67, 71, 72, 89, 92, 96, 97, 101–103, 127,

128, 130, 132, 136, 138Focal glow 24, 116Fovea 37

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Fresnel lens 16, 91, 92, 102

Gas light 17, 20, 43General service lamp 127General lighting 13, 22, 24, 78, 99, 101, 102, 104, 127, 136–139, 141Gestalt perception 33, 34, 147Glare 12, 22, 39, 74, 79, 80, 89, 90, 99, 105, 114, 143Gobo 73, 92, 102, 144

High-pressure fluorescent lamp 21, 55, 56, 66, 73, 123High-pressure mercury lamp 57, 127, 128, 130High-voltage fluorescent tubes 21, 55, 56, 66, 73, 123

Ignition aid 54, 59, 71, 72Ignitor 58, 59, 61, 65–67Illuminance 15, 22–24, 31, 37, 39, 42, 71, 73–78, 84, 110, 112, 113, 115, 116, 119, 126,

128, 130, 138, 150, 154, 155, 157, 158, 168, 169Illuminance at a point 154, 158Incandescent gas light 18Incandescent lamp 21, 25, 43, 45, 47, 49, 50, 52–55, 58, 65, 71, 83, 96, 101, 102, 103,

104, 127, 128, 130, 132, 138, 157, 158, 169Inductive circuit 65–67, 71, 72Infrared radiation 88, 92, 132, 143Interference 87Inverse square law 42, 158Involute reflector 90Isoluminance diagram 158Isolux diagram 158, 160

Lead-lag cicuit 67Light output ratio 85, 94, 98, 155, 157, 158, 169Light control 15, 16, 85, 87, 90, 92, 98, 127Light loss factor 157, 169Light output ratio 154, 155, 157, 158Lighting control 25, 73, 126, 135, 136, 144, 150Line spectrum 52LiTG 155LLB 65Louvred luminaire 55, 80, 97–100, 104, 135–138, 143, 144, 147, 152, 153, 157Low-pressure sodium vapour lamp 56, 57, 66, 128Low-voltage halogen lamp 49, 127, 128, 130Lumen, lm 40, 41, 130, 158Luminaire classification 143Luminaire efficiency 154, 155, 157, 158Luminance limiting method 81Luminance 31, 37–39, 75, 76, 79, 80, 99, 112–114, 143, 160Luminescence 17, 18Luminous efficacy 17, 18, 21, 22, 40, 45, 47, 49, 52, 54–56, 58–60, 65, 128, 130, 132,

157Luminous colour 18, 32, 33, 45, 49, 52–54, 56–58, 60, 71, 73, 78, 83, 84, 88, 110, 119,

122, 126–128, 143, 144, 150, 169Luminous intensity 22, 37, 103, 119, 128Luminous intensity distribution 41Luminous flux 40, 105, 128Lux, lx 37, 74, 75, 84, 111, 114, 157

Mesopic vision 37Metal hailde lamp 43, 59, 103, 105, 127, 128, 130Mode of Protection 143Modelling 77, 78, 97, 114, 126, 127, 137, 138, 144Modular luminaire 97

Neutral white 54, 60, 128Night vision 37

Optical fibre 105

Parabolic reflector 89, 90Perceptual psychology 24, 29, 113Phase angle control 71Photopic vision 37

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Planckian radiator 83Play of brilliance 24, 116Point light source 53, 91, 116Power factor 67Prismatic louvre 91, 92, 97, 98Protection class 143

Reflected ceiling plan 160Reflected glare 79–81, 98, 105, 111, 119, 137, 138, 143, 147Reflection 12, 78, 85, 113, 127, 138Reflector 16, 47, 50, 80, 85, 87, 88, 91, 98, 102, 127, 132, 169Reflector lamp 58–60, 85, 102, 127Refraction 78, 87Refraction of light 92, 127Re-ignition 54, 56, 57, 59–61, 67Relative glare 79Retina 28–33, 37, 75, 76, 79, 113, 114Rods 37Room index 157

Scallop 94, 139Scotopic vision 37Secondary reflector technology 105, 136–138Self ballasted mercury discharge lamp 58, 59, 65Shadow formation (modelling) 78, 110, 154, 158, 168Spherical reflector 90Spherical aberration 28Standard colorimetric system 83Starter 54, 55, 65, 66Steradian 41Stroboscopic effects 65, 67Sun simulator 167Sunlight 12, 13, 23, 31, 33, 37, 43, 76, 78, 89, 122, 150Surround field 79, 112, 114, 136

Tandem circuit 67Task lighting 22, 75, 78, 80, 110, 111, 114, 128, 136, 138, 143Thermal radiator 43, 45, 84Transformer 49, 65, 67–69, 71Transmission 85Halogen lamp 25, 43, 45, 49, 50, 71, 96, 101–104, 127, 128, 130, 132, 169

Ultraviolet radiation 45, 53, 54, 56, 87, 88, 92, 102, 132, 143Utilance 155, 157

VDT-approved 99, 105Visual task 22, 24, 39, 72, 74, 75, 78–81, 84, 111, 112, 115, 117–119, 137–139, 141Visual comfort 87, 105, 138Visual accuity 37, 57

Warm white 49, 54, 60, 128Working plane 110, 138, 154, 155, 158, 168

Zoning 112