principles of prepress

© 2004 Print Media Academy • Wolfgang Wallowy • Principles of Prepress.ppt

Offset Printing Technology

Principles of Prepress

• • • • • • • • • • • • • • • •• • • •

• • • • • • • • • • • • •Print Media Academy

© 2004 Print Media Academy • Wolfgang Wallowy • Principles of Prepress.ppt 2

Contents:

• The way to the digital workflow• The production steps• History• Reproduction – What’s that?• The original copy: Text, graphic, picture• Digital data • Fundamentals of color theory• From the original to the printing plate• The Screen• Postscript, PDF, PPF, JDF, CIP...• The workflow• Color management• Standardization• Output and process automation• Prinect MetaDimension• Proofing and PDF workflow• Imposition – digital full pages• Computer-to-Plate equipment technology

• • • • • • • • • • • • • • • •• • • •



The production process of printed products

Prepress Press Postpress

• • • • • • • • • • • • • • • •• • • •



Possible workflows in prepressImages are scanned, electronically processedand positioned, then separated and screened

RIPFilm processing

Film proofing

Film checking

Plate making

Plate development

PrintingComplete processingof A3 signatures

Digital proofing

RIPPlates are directlyimaged in thepress and printed

Complete processingof signatures

Digital proofing

RIP

Hard and soft proofing

Plate exposureand development

Printing

• • • • • • • • • • • • • • • •• • • •



A prepress workflow in general

Plate ( Film) imaging

CIP4 ProcessingScan & image processing( Scanner or Digital Camera)

Layout, text & graphic workstation

Single pages proof stationcolor- & text correction

Server( Data Manager)

Digital sheet assembly( imposition scheme)

Form proof(proof of complete print form)

Data exchangewith press and finishing

External Data

• • • • • • • • • • • • • • • •• • • •



The way to the digital workflow

Prinect Prepress Interface

FoldingCutting

PC

PrinectPrintready System

Database

PrinectSigna Station

Internet Portal

PrinectPrinance

PrinectData Control

Stitching

PrinectPrint Center

PrinectCP2000 Center

• • • • • • • • • • • • • • • •• • • •



Distributed tasks in the past

Repro house

Compositor

Assembly

Printing houseAgency

• • • • • • • • • • • • • • • •• • • •



Reproduction – What was is that?

The photographic masks, called repro films or lithos, were “photographed“ mainly with large-size repro cameras:

- Color separations were exposed with RGB color filters and corresponding correction masks on special sensitive films

- Screens were produced with engraved glass screens or contact screens- The finished lithos were then – depending on the printing method – assembled

one over the other and true to register on transparent polyester foil

Klimsch Repro devices of the19seventies

• • • • • • • • • • • • • • • •• • • •



What is an original copy?

The original copy comprises the following elements:

- Picture- Text/type- Graphic

These elements are created by means of scanners, digital cameras, application software

Picture

Scanner,digital

camera

ABCText

Computer, software,

fonts

Graphic

Computerand

software

• • • • • • • • • • • • • • • •• • • •



Fundamentals of color theory

• • • • • • • • • • • • • • • •• • • •



Fundamentals of color theoryWhat happens in the head ?

• The color receptors of the human eye react to colors• Cone-shaped receptors = color• We recognize the three main fields red – green – blue• Rod-shaped receptors = black, white, gray

• • • • • • • • • • • • • • • •• • • •



How the human eye perceives light

Whitelight

Lightsource

Prism

Prismatic colors

Color receptors of the eye

• A prism splits sunlight or white artificial light into prismatic (rainbow) colors of the electromagnetic spectrum

• So WHITE is the sum of all colors; BLACK, i.e. no light, means no color• The so-called color receptors of the eye (red, green and blue) receive these pieces

of the picture, the brain then combines all this information in one “color“ picture

• • • • • • • • • • • • • • • •• • • •



Additive color mixing

• Red, green and blue are the base colors of additive color mixing (TV, monitor, beamer, video)

• If a white area is illuminated with three spot lights in red, green and blue, the eye perceives a white spot where the three light bundles overlap

• The addition of two base colors generates lighter complementory colors

• • • • • • • • • • • • • • • •• • • •



Subtractive color mixing

• The base colors in subtractive color mixing are cyan, magenta and yellow.

• Overprinting, they add up to black• The white paper serves as the reflector• The more color is applied to the paper,

the more light is reduced• Color absorbs its own complementary

color and reflects its own inherent color• Autotypical color synthesis

• • • • • • • • • • • • • • • •• • • •



From the original to the printing plate

The way from the original to the printing form/printing plate:• Creation of the document• Page layout, text, graphic• Scanning of pictures• Integration of all elements• Imposition, if required• Transformation of the computer data

into an imageable bitmap• Exposure of the film or the

printing plate (on-press or off-press)

• • • • • • • • • • • • • • • •• • • •



Scanning

• By scanning strip by strip and step by step as well as through the color separation with the RGB filters, 3 bitmaps are generated for red, green and blue

• With an appropriate software, RGB are converted into cyan, magenta and yellow taking into account the necessary corrections

• Black is generated by using a special color filter or by calculating it as the fourth bitmap

• The precision of many scanners allows to reconvert screened films into bitmaps (copix)

• • • • • • • • • • • • • • • •• • • •



Data input is complete and ready for output

• All elements, i.e. picture, type (text) and graphic, are combined into one unit, i.e. one or more pages, one document, on a workstation

- The documents are now ready for a digital specimen print, for imposition or for exposure on film or printing plate or direct imaging to press

Type

TypeABC

• • • • • • • • • • • • • • • •• • • •



How the digital code works

AaBb12

ASCII-Code

010000010110000101000010011000100011000100110010

MorseSignals

· -

- · · ·

· - - - -· · - - -

• Computers use the binary code, i.e. the representation of information with the figures 0 and 1 = 1 bit (binary digit)

• A group of 8 bits forms one byte, i.e., one of 256 definition or switch possibilities:1 bit = 2 switch conditions 0 or 1,2 bits = 4 switch conditions8 bits = 256 switch conditions = 1 byte

• • • • • • • • • • • • • • • •• • • •



The Bitmap

0 0 0 0 0 1 1 1 0 0 0 0 00 0 0 0 0 1 1 1 0 0 0 0 00 0 0 0 1 1 1 1 1 0 0 0 00 0 0 0 1 1 1 1 1 0 0 0 00 0 0 0 1 1 0 1 1 0 0 0 00 0 0 1 1 1 0 1 1 1 0 0 00 0 0 1 1 0 0 0 1 1 0 0 00 0 1 1 1 0 0 0 1 1 1 0 00 0 1 1 1 0 0 0 1 1 1 0 00 0 1 1 1 1 1 1 1 1 1 0 00 1 1 1 1 1 1 1 1 1 1 1 00 1 1 1 0 0 0 0 0 1 1 1 00 1 1 0 0 0 0 0 0 0 1 1 01 1 1 0 0 0 0 0 0 0 1 1 1

• The digital, geometric representation in a kind of chessboard pattern is used with image data (scanners, digital cameras) and for controlling printers and exposure units

• This format of digital representation is also called bitmap. It is a map consisting of bit (or byte) data, i.e. of pixels or picture elements

• The fineness or resolution is expressed in dots per inch (dpi)

• • • • • • • • • • • • • • • •• • • •



The Vector Format

TypeType

• Besides the bitmap format for pictures, there is the so-called vector format for line art and text in which all elements are defined by geometric formulas, e.g. Bezier curves

• These vector data are not converted into the known bitmaps until the output on a printer or exposure unit

• The advantage of vector data is that they are independent of size and resolution, e.g. withtypefaces, smaller quantity of data

• • • • • • • • • • • • • • • •• • • •



The Screen

• Why is a screen used?• With all known printing methods of letterpress and

offset – gravure printing is an exception. In order to create visual tonal gradations the screening technique is used

• Gray values are represented by dots of different diameters, mostly in a regular arrangement (therefore: screen)

• The human eye mixes the different reflection intensities thus created into one gray tone or graded halftone

• • • • • • • • • • • • • • • •• • • •



The Screen Angle

• When 2 screened images are printed on top of each other and their screen angles are not in perfect register, a moiré pattern may occur

• The screen angle relationship of 30° is common

• Since 3x30° means 90°, a 4th color would lie on one of the already existing angles

• Yellow distinguishes only little from the paper white and the other colors, therefore a special trick is used, i. e. yellow is positioned at an angle of 15° in relation to 2 colors, mostly on 90°

Standard angle positions

• • • • • • • • • • • • • • • •• • • •



Screen Ruling

Schematic representation of a screen of an approx. 30% tone value and at an angle of 105°

• The distance between the dots is called screen ruling

• There is a rule: A coarse screen for bad paper grades (coarse surface) like newsprint paper, a fine screen for coated paper grades (art paper)

• For art paper, normally screen rulings of 60-70 l/cm are used, with the modern print quality, it is no problem to print much higher screen rulings

• • • • • • • • • • • • • • • •• • • •



Screen Construction

• With an imaging resolution of 100 l/cm, there is a basic area of 16 x 16 spots for every dot between 0% -100%

• Thus it is possible to represent 256 tone values per dot, enough for the human eye

• Under these conditions, an output devicerequires a total of 0.921 mio. commands in order to switch the laser beam on or off for all spots on an area of 1 cm2

Halftone valueapprox. 82%

• • • • • • • • • • • • • • • •• • • •



The Raster Image Processor (so-called "RIP")

Layout/Document

Type

Type

• The production of the bitmap to be printed and the allocation of the screens for halftone pictures / sets of color separations takes place in the so-called RIP process with the original CMYK image data and the original typefaces being used

• It is based on the PostScript page description language (Adobe) and a suitable software on a standard computer platform (Software-RIP, e.g. Prinect MetaDimension)

• In printers, the RIP is in the device itself (Hardware-RIP)

• • • • • • • • • • • • • • • •• • • •



What is behind the terms PostScript , PDF, PPF, JDF, CIP ...?

• • • • • • • • • • • • • • • •• • • •



What is PostScript?

PostScript is a page description language fromPS achieved its breakthrough with the launch of the first RIP (raster image processor) by Linotype in 1985 for the Linotronic 300 from Linotype-Hell AG

Important PostScript components are e.g.the programming language,the printer driver, andan interpreter (RIP) as well as Type 1-fonts

• • • • • • • • • • • • • • • •• • • •



What happens in the PostScript-RIP?

• Application-specific modifications are realized, e.g. distorting, image enlargements, gradation adjustments, etc.

• Graphic elements (pictures, graphics) are converted into screens, including screen angles, screen ruling, dot shape and calibration (e.g. print characteristic curve)

• For every color, a separate bitmap is generated in black and white

%!PS line width/zoll {72 mul} def/rechteck % Routine{newpath.6 .4 moveto -.6 .4 lineto-.6 -.4 lineto .6 -.4 lineto

closepath} def

gsave5 zoll 3 zoll translate1 16 div setlinewidth1 1 6 % Schleife 1 bis 6{gsave.5 mul zoll dup scale %

multiplizierenrechteckstroke

grestore} for % Schleifen-

Endegrestoreshowpage

• • • • • • • • • • • • • • • •• • • •



What is PDF (Portable Document Format)?

• PDF is a page-oriented PostScript data format which can easily be produced (PDF-writer/printer driver), in which superfluous command and definition structures are eliminated (lean PS) and which can be represented and – to a limited extent –edited with simple tools (Adobe Acrobat Reader, Freeware) across different platforms

• It even simulates missing fonts with an approximate character width and approximate font characteristics

Wor

kflo

w

PDF view

Prep

ress

PDFprinterdriver

PDF fileDocument

• • • • • • • • • • • • • • • •• • • •



Prinect Prepress Interface

Digital Imposition RIP Printing PlatesComputer-to-Plate

Or via online connection

Job Memory Card

Ink Zone Profiles

Print ProductionFormat PPF

PrepressInterface

CIP4

• • • • • • • • • • • • • • • •• • • •



From Print Production Format towards Job Definition Format

Introduction DRUPA 1995

Horizontal Integration of Production Workflow

• PPF-Format (Print-Production-Format):A PPF-file can contain the following data:

- Job and commercial data- Low-res bitmaps of the printed sheets- Transfer curves- Register marks- Color and density measuring points- Cutting, folding and stitching folding data

Introduction DRUPA 2000

Vertical and horizontal Integration ofProduction and Business Workflow

• The PPF-format can be used for: - Automatic ink zone setting- Make ready of cutter, folding and

stitching machines

• • • • • • • • • • • • • • • •• • • •



• The automation of the production processes in the printing industry has made great progress over the last few years

• Within the classic production units prepress, press and finishing, production can be highly automated, on the condition that it is an environment from just one manufacturer

• Standardized data formats as CIP 4 bridge the borders between Prepress, Press and finishing and production data capturing

Scanner Film-/ Platesetter

Printing Press Cutting-/ Folding Machine

Workstation

JDF Actual Data

JDF Planned Data

3rd PartyMachines

and Software

What is JDF (Job Definition Format)?

• • • • • • • • • • • • • • • •• • • •



... and to make sure it really works, a standardized color work flow from input through to printing

Color Management is a precondition and a tool for matching all components involved in a workflow with a preset standard

The Digital Proof- Simulates the print run on the printing press- Is a preview of the printing result- Requires appropriate resolutions and repeat accuracy

Standardization

Calibration

Profiling

Applications

• • • • • • • • • • • • • • • •• • • •



Why Color Management ?

Press

Scanner

Proofer

Monitor

• • • • • • • • • • • • • • • •• • • •



Color Management

• Graphical representation of color spaces described by ICC profiles

• Color spaces have different shapes and dimensions.

• Every device has its own speciallydefined color space

• • • • • • • • • • • • • • • •• • • •



Targets of Print Color Management

ICC-Profile Proofs and standardized print

Optimizing of Printing press

Optimizingof PrePress

Standardization

Process control

• • • • • • • • • • • • • • • •• • • •



We must have a common order!

With the device-independentCIELAB color space

• • • • • • • • • • • • • • • •• • • •



-b

+b

+a-a

-b

+b

+a-a

Commission Internationale d’Éclairage (CIE)- Specification of the Lab color space 1976- Device-independent,- Based on human color perception

International Color Consortium (ICC)- Specification of the ICC profile format 1994- Computer-independent,- Manufacturer-independent

Color Management is based mainly on international standardization

• • • • • • • • • • • • • • • •• • • •



With precise color space descriptions

In the form of ICC profiles

Classified for scanners, monitors andprinters / proofers / printing presses

• • • • • • • • • • • • • • • •• • • •



Color Management !

Press

Scanner

Proofer

Monitor

• • • • • • • • • • • • • • • •• • • •



High-performance PDF and PS 3-RIP

Open PDF workflow- Combinations with Prinect SignaStation, Prinect Printready System,

Prinect MetaDimension and Prinect MetaShooter, etc. are available according to requirements

- Open for any “self-made PDF workflows” with Acrobat plug-ins and applications

• • • • • • • • • • • • • • • •• • • •



Preflow: Generation of a perfect PDF!

• JobStream generates a clean PostSriptpreflight PDF after the distiller

- Pitstop for PDF-editing and preflight check

- Pitstop Server for automatic preflight of large quantities of documents and revisions of the PDFs

• Interactive trapping of PDF with Supertrap• Optimized PDFs for Prinect MetaDimension

for imposition, form and color proofing, output on film or plate

• State of the Art PDF trapping• Very fast and easily operated Acrobat plug-in

- Interactive and automatic- Standard and user-defined parameters- Efficient spreading of special colors- Image-to-image spreadings

• • • • • • • • • • • • • • • •• • • •



What’s imposition, please?

The term imposition describes the arrangement of pages on a print sheet taking into account the finishing steps in finishing:

- like folding,- collecting,- and binding technologies like adhesive

binding, saddle stitching/thread stitching

The arrangement of the pages is always defined by the sequence of pages and the dimensions of the individual pages

• • • • • • • • • • • • • • • •• • • •



2 15 14 37 10 11 6

• The folding schemedetermines thearrangement of thepages

• The pages are brought into the desired sequence by folding

• After trimming at three sides, the „copy book“ can be opened

The print sheet

• • • • • • • • • • • • • • • •• • • •



Advantages and disadvantages of digital printing plate production

• Very short production times• Very high quality of the printing plates• Maximum register-trueness• Less make-ready times in printing• Less waste

• All elements need to be available in a digital form, e.g.

- print control strip- process control strip- cutting – folding marks

• Redigitization of old data is necessary • Digital proof systems are required

• • • • • • • • • • • • • • • •• • • •



Equipment technology

• • • • • • • • • • • • • • • •• • • •



Imaging techniques and design features

Internal drum imagesetterExternal drum imagesetter

Modern imagesetter technologies comprise the following 3 categories – listed by production expenses:

- Capstan imagesetters work via a polygon onto material on a roll which is transported in a synchronized way with the rotation,

- Internal drum imagesetters expose onto fixed material (sheets cut from a roll),

- External drum imagesetters direct the laser beam strip by strip onto a rotating drum holding the material to be exposed.

• • • • • • • • • • • • • • • •• • • •



The Capstan Principle

• Costly synchronization of optical system• Adjustment of light intensity between the

center and the edges of the material (beam length differences)

• Suited for film and polyester plate• Comparatively low production costs• Link to online processor

Laser source

Polygon

Film material

• • • • • • • • • • • • • • • •• • • •



The Internal Drum Principle

• Costly production of the internal drum, fixed film, high repeat accuracy

• Identical beam length in all positions• Simple optical system (prism)• Only 1 laser beam for imagesetting, from roll to

sheet, roll to roll• Link to online processor,• Integrated register • Punching system for film

and polyester plate

© 2004 Print Media Academy • Wolfgang Wallowy • Principles of Prepress.ppt

Offset Printing Technology

Principles of Prepress

Back to Selection

principles of prepress

Documents

prepress workflow

digital cameras

digital cameralayout

original copy

color separations

printing plate

repro films

rgb color filters