basics of color theory powerpoint

8/10/2019 Basics of Color Theory Powerpoint

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THE BASICS OF COLORPERCEPTION ANDMEASUREMENT


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The Basics Of ColorPerceptionan Meas!re"entThis is a tutorial about color perception and m

It is a self teaching tool that you can read at ypace.

To go back one slide click.

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Contents

There are ve sections to this presentatio

Color Perception

Color Meas!re"ent

Color Scales

S!rface Characteristics an #eo"etr$

Sa"ple Preparation an Presentation

If you wish to !ump to a specic section click aappropriate name or click below to advance toslide.


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COLOR PERCEPTION


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Thin%s Re&!ire To See Color

" #ight $ource

"n %b!ect

"n %bserver


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'is!al O(ser)in% Sit!ation

#I&'T

$%()*E

%+E*T


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'is!al O(ser)in% Sit!ation

To build an instrument that can uantifycolor perception, each item in the visuaobserving situation must be representedtable of numbers.

The visual observing model shows the t

necessary to perceive color.


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Li%ht So!rce


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Li%ht So!rce

" light source emits white light.

When light is dispersed by a prism, all viswavelengths can be seen.


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S!nli%ht Spectr!"


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Li%ht So!rce

-isible light is a small part of the electrospectrum.

The wavelength of light is measured in n/nm0.

The *IE wavelength range of the visible from 123 to 453 nm.

" plot of the relative energy of light at eawavelength creates a spectral power discurve uantifying the characteristics of tsource.


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Spectral Po*erDistri(!tion of S!nli%ht

133 673 773 273

'ISIBLE SPECTRUMULTRA'IOLET

+

,+

-++

-,+

./+ ,++ /++

2a)elen%th 3 Nano"eters 4n"5

Relati)e

Ener%$

Da$li%ht


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Li%ht So!rce )ers!sIll!"inant

" li%ht so!rceis a physical source of li

" CIEill!"inantis a standard table of representing relative energy versus wavthe spectral characteristics of light sour


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Li%ht So!rce )ers!s Ill!"inant

Da$li%ht T!n%sten

So!rce

Ill!"inant

6++ ,++ /++0++ 2a)elen%th 4n"5

E7

2a)elen%th 4n"5

6++ ,++ /++0++

E7D

/, A

E7

6++ 0+


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So"e Co""on Ill!"inants

A Incandescent

C "verage 9aylight

D/, :oon 9aylight

F8 *ool White ;luorescen


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CIE Ill!"inant

+y representing a light source as anilluminant, the spectral characteristicrst element of the -isual %bservinghave been &!anti9eand stanar


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927


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O(


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O(


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Li%ht Interaction *ithSchool B!s Paint

Incient

Li%htDi>!se

Re=ection


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O(


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Spectrophoto"etric C!r)efor ?School B!s @ello*

2a)elen%th 4Nano"eters5

CR

ela

ti)eRe=ectance

6++ ,++ /++

+

8,

,+

0,

-++


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O(


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)e


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O(ser)er


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H!"an O(ser)er

Ros in the eye are responsible for

vision.

Conesin the eye are responsible fovision and function at higher light l

The three types of cone sensitivitiere, %reenand (l!e.


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Li%ht

)etina

Li%ht

)etina

The H!"an E$e


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CIE Stanar O(ser)er

Experiments were conducted to uantify the athe human eye to perceive color.

" human observer looked at a white screen thaperture having a = degree eld of view.'alf of a screen was illuminated by a test light

The observer ad!usted the amount of three prcolored lights on the other half of the screen u

matched the test light color.

This process was repeated for colors across thspectrum.

Deter"ination of Stanar


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RED#REEN

BLUE

TESTLI#HT

2HITEBACDROP

REDUSCRE

BLAC PARTITION

TESTFILTER

=>

Deter"ination of StanarColori"etric O(ser)er


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CIE Stanar O(ser)er

These functions uantify the red, greblue cone sensitivity of the average observer.

The experimentally derived $ anfunctions became the CIE -G.- 8 O(ser)er.

? ? ?


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+;+

+;,

-;+

-;,

8;+

CIE 8 Stanar O(ser)er

Tris

ti"!l!s'al!es

6++ ,++ /++

:

$

3

33


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O(ser)er

When the 8@18 => $tandard %bserver were conducted, it was thought that thconcentration was only in the fovea re

#ater it was determined that the conesbeyond the fovea.

The experiments were reAdone in 8@26resulting in the 8@26 83> $tandard %bs


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8 an -+ O(ser)er

0 Feet

.

-,

8

-+

8 )ers!s -+ CIE Stanar


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8 )ers!s -+ CIE StanarO(ser)er


Tristi"!l!s'al!es

6++ ,++ /++

+;+

+;,

-;+

-;,

8;+ 3

3 3

:

$

(


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CIE Reco""ene O(ser)er

%f the two observers, the *IE recommen

$tandard %bserver. It best correlates withvisual assessments made with large eldtypical of most commercial applications.

O(


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O(ser)er

The three elements of the -isual $ituation have now been uantienumbers.

The Li%htSo!rceis a userAselectilluminant.

The O(


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)e


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COLORMEASUREMENT

Thin%s Re&!ire


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Thin%s Re&!ire

To See Color To Meas!re Col

Li%htSo!rce

O(


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Color Meas!re"ent

The CIE @ Jtristi"!l!s color )al

obtained by multiplying the illuminantre


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6-

*IE B

*IE C

*IE D

*IE Illuminant 927

)e


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Meas!rin% Color

" Colori"etric Spectrophoto"eter ussource to illuminate the sample being me

This sample signal falls onto a diode arrathe amount of light at each wavelength.

The light re


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Meas!rin% Color

Li%htSo!rce

Dioe Arra$Sa"ple

Di>raction#ratin%

H!nterLa( Spectrophoto"eter


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S$ste"s

MiniScan EJF

ColorFleEJ

F

La(Scan EF

UltraScanPRO

F

Color!estT

F

Color


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COLOR SCALES

'is!al Or%ani:ation of Color


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"ll colors are organied in three dimensioLi%htness, Chro"aor Sat!ration, and



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SATURATIONCHROMA

LI#HTN

ES

S

LI#HTNE

SS

2hite

Blac

HUE


Meas!re Color 'al!es


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Meas!re Color 'al!es

-isual evaluation of color is s!(


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Meas!re 'al!es

H @H JH

Color Scales


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In terms of ob!ect color, B, C, D values are nunderstood. %ther color scales have been d

+etter relate how we perceive color.

$implify understanding.

Improve communication of color.

+etter represent uniform colordierences.

Opponent3Colors Theor$


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pp $

$tates red, green and blue cone response

remixed into opponent coders as they mothe optic nerve to the brain.



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CO

L

O

R

BLUE

RECEPTOR

#REENRECEPTOR

REDRECEPTOR

BLUE3@ELLO2

CODER

BLAC2HITCODE

RED3#REENCODER

pp $



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When the next slide appears, focus on the

cross in the center of the stripes until theautomatically changes to the white screeabout =3 seconds0.


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9id you see the stripes as red, white and blueJ

This happens because the green, black and yesaturate the cone responses.

When you look at the blank screen your vision to balance and you see a red, white and blue a

This e"onstration s!pports the OpponeTheor$

H!nter La( Color Space


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'unter #,a,b color space is a 1Adimensional rcolor space based on %pponentA*olors Theor

L/lightness0 axis A 3 is black, 833 is wand 73 is middle gray

a/redAgreen0 axis A positive values a

negative values are green, and 3 is n

(/blueAyellow0 axis A positive values yellow, negative values are blue, andneutral

H!nter La( Color Space


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H!nter L a ( Color Space


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"ll colors can be represented in #, a,

rectangular color space.

The following slide shows where KschyellowL falls in 'unter #, a, b color sp


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#REEN

@ELLO22HITE

BLUE

3.+

3

8+3

-+-

+

8+

.+

LI#HTNESS

RED

3.+

38+

3-+

36+

-+

8+

.+

6+

-++

BLAC

/+

0+

1+

G+

-++

8+

.+

H!nter L a ( 'al!es for?School B!s @ello*


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# H 28.6a H M 85.8b H M 1=.=

L a ( Color Scales


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There are two popular #,a,b color sca

today H!nter La(and CIE LQaQ(

While similar in organiation, a color wdierent numerical values in these twspaces.

H!nter L a ( )ers!s CIE LQaQ (Q


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# N HaN H

bN H

# H 28.6=a H M 85.88

b H M 1=.=1

CIE LQH!nter L a (-G,1

L a ( Color Scales


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'unter #, a, b and *IE #N,aN,bN scales are mathematically derived from *IE B, C, D v

:either scale is visually uniform. 'unter over expanded in the blue region of coand *IE #N,aN,bN is over expanded in thregion.

The c!rrent CIE reco""enation is tLQaQ(Q;

Calc!lation of Color For"!las


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L K -++ @@n-8

a K a n3@@n

@@n-8

( K ( @@n3 JJn

@@n-8

H!nter L a (

LQ K --/ @@n

aQ K ,++ 4

@@n-.5

(Q K 8++ 4@@

JJn-.5

CIE LQ aQ

2hat is an Accepta(le ColorDi>erence


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Mini"!" Percept

Mai"!" Accept

2hat is an Accepta(le ColorDi>erence


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What is an acceptable color dierence vathe application.

;or example

What is acceptable for color matchingautomotive paint is close to being a "percepti(lelimit.

What is acceptable for snack foods is and the "ai"!" accepta(le li"itthe tolerance for the product.

Rectan%!lar LQ aQ (Q ColorDi>erences


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*olor 9ierences are always calculated asSAMPLE 3 STANDARD values.

If elta LQis positi)eO the sample is li%htstandard.If ne%ati)eO it would be arer than the s

If elta aQis positi)eO the sample is "or%reen0than the standard.

If ne%ati)eO it would be "ore %reen/or l

If elta (Qis positi)eO the sample is "orless (l!e0 than the standard.If ne%ati)eO it would be "ore (l!e/or le

Rectan%!lar LQ aQ (Q ColorDi>erences


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SAMPLE STANDARD

DIF

LQ K0-;GaQ K-+;8(Q K,1;-

LQ K/G;0aQ K-8;0(Q K/+;,

L8 a8;

(8;6

Delta EQ Total ColorDi>erence


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EQis based on LQaQ(Q color dier

and was intended to be a single nummetric for PASSFAIL decisions.

Delta EQ Total Color Di>erence


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LQ

aQ

Sa";

EQ K LQ 8 aQ 8 (Q 8


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SURFACECHARACTERISTICS #EOMETR@

Re=ectance of Li%ht


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;or opaue materials most of the incident light

*olor is seen in the diuse re


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Incident #ight 9iuse)eect of S!rface Tet!re onPercei)e Color


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$amples that are exactly the same color, dierent surface textures, will appear di

&lossy surfaces appear darker and more s

Gatte and textured surfaces appear lighte

less saturated.

E>ect of S!rface Tet!re onPercei)e Color


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#los

Matte

Ro!%h

E>ect of S!rface Tet!re on Percei)eColor


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Increased surface roughness aects percesuch that it appears lighter and less satur

This is caused by mixing diuse re


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Matte Se"i3#loss Hi

Instr!"ent #eo"etr$


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Instrument geometry denes the arrangem

light source, sample plane and detector.

There are two general categories of instrugeometries

Directional/67>Q3> or 3>Q67>0 and i>!s

sphere0.

Directional #eo"etr$


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Directional 6,+geometry has illumin67> angle and measurement at 3>.

The inverse +6,geometry has illuminand measurement at 67>.

+oth exclude the specular re


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+

6, Ill!"ination+ Meas!re + Ill!"inaMeas

Spectrophoto"eter

Speci"en Speci"en

6,

Di>!se

Di>!se

Spec!lar

So!rce

Sp

Di>!se

+

So!rce

#loss E>ect on Color Di>erenceMeas!re"ent


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%n the following slide the paint on the card is the samthe entire card. The right side has a matte surface nside has a high gloss nish.

The color dierence measurement, made using a direinstrument, indicates a color dierence that agrees wevaluation /the matte side is lighter and less red0.

9irectional instruments measure both the eect of ththe eect of the surface nish. They are appropriate f

control applications where agreement with what you important.



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#loss$

M

LQ aQ(Q

Spec!lar Ecl!e -;6 3-;,3-;8

Directional +6, #eo"etr$

A +6, #eo"etr$Spectrophoto"eter


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La(Scan EF

Di>!se #eo"etr$

9i / h 0 t i t t


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9iuse /sphere0 geometry instruments use a wsphere to diusely illuminate the sample with 5viewing.

Geasurements on a diuse sphere instrument with the spec!lar incl!e or ecl!e.

Di>!se #eo"etr$

S l I l t


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Spec!lar Incl!e measurements nedierences and provide values which corresponcolor.

Spec!lar Ecl!e measurements negate spre


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Spec!lar Incl!e Spec!lar

Spectrophoto"eter

Spectrophoto"eter

Sa"ple

Meas!re

Sp

ec!la

r



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%n the next slide measurements were taken on thusing a diuse dQ5> sphere instrument.

The specular included measurement indicates no It uanties only colorant dierences and negate

surface nishes.

In the specular excluded mode, the readings uandierences, similar to those from the 3>Q67> instr



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#loss$

M

LQ aQ(Q

Spec!lar Incl!e +;+ +;-3+;+Spec!lar Ecl!e -;1 3-;/3+;G

Sphere #eo"etr$

Tet!re E>ect onColor Di>erence Meas!re"ent


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#N aNbN$pecular Excluded 7.= 8.5 =.7

#N aNbN$pecular Included 3.8 A3.8 3.8

$pecular Excluded =.3 3.7 8.3

Li%ht Tet!re Hea)$ Te

Sphere #eo"etr$

+6, #eo"etr$

Sphere #eo"etr$ forTrans"ission

$phere geometry instruments also have the ab


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p g ymeasure the color of transmitted light.

Total Trans"ission is a combination of regdiuse transmission.

Di>!se Trans"ission also contains color o

material.

$urface texture or internal scattering within can cause the light to scatter or diuse.

*olor is seen primarily in Re%!lar Trans"istransmits straight through transparent solids

Trans"ission of Li%ht


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Incient

Li%ht

Spec!lar

Re=ection

Di>!seTrans"ission

RTran

Total

Sphere Instr!"ent Meas!rin% inTrans"ission


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Color!est EF


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SAMPLEPREPARATION PRESENTATION

Ieal Sa"ple For ColorMeas!re"ent


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(niform$mooth

;lat

$olid

%paue or transparent

Sa"ple Preparation anPresentation

*h l th t t ti


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Take multiple readings of the sample for ameasurement.

*hoose samples that are representative oproduct.Rrepare the sample in a way to best appro

the ideal sample characteristics.

Rrepare samples in the same way each tim

Rresent the samples to the instrument in arepeatable manner.

Ea"ples of Sa"ple Preparationan Presentation


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Than @o!

If you are connected to the internet click


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;or more information about sample

and presentation

;or product information

visit our website at ***;h!nterla

or

contact us at infoVh!nterla(;co"
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