Electronic Prepress and Digital PrintingChapter 9

Computer Platforms The platform of an electronic imaging system is the

computer system (hardware) that is used to operate software Word processing Page composition Drawing creation

PC (IBM personal computer) Macintosh (Apple) Applications, formats, or devices that work on

different platforms are CROSS-PLATFORM Common Hardware Reference Platform (CHRP)

Text (Content Creation) Word processing programs

Assign codes and format to text Styles or tags

Page composition programs Recognizes formats

ASCII files (American Standard Code for Information Exchange) Formatting is lost, but text can be repurposed Reusing content intended for one medium by reformatting it for

another Transfers data from one computer to another

IMPORTANT: Maintain original text and image files Make copies and work from copies

Creating Computer ImagesPaint programsDraw programsDigital photographyElectronic scanning

Paint ProgramsFreehand drawings, easily editedBitmaps or raster graphicsGrid of pixels, filled in or emptyEnlarging bitmaps creates jagged edges

because resolution is reduced (aliasing)Antialiasing diminishes jagged edges, fuzzierSmoothing also reduces jagged edges

Draw ProgramsVector graphics, object-oriented graphics

line defined by start and end point

Can be scaled and represented at any resolution (high resolution output)

Bezier curve is a vector graphic defined by two endpoints and two or more other points that control shape (anchors, handles)

Review Questions1. What is meant by cross-platform?2. Reusing content intended for one medium by

reformatting it for another is called _______3. List four methods that can be used to create

computer images4. What are two methods for diminishing

jaggies that should be smooth?

Manipulating ImagesAdobe Photoshop

Cropping Color and Contrast Adding or removing visual information Combining images Sharpen, Blur, and Smudge edges Mix, Choose and Apply colors Paint and Draw Clone Apply Filters Create Gradients and Textures

Raster Image Processors (RIP)Vector graphics information is transferred from a design

workstation to a RIP Hardware-software combination that converts vector images into

bitmapped images at selected output resolution View screened files before imaging Supports many font types Offers different dot shapes Can drive multiple output devices simultaneously Interprets and separates color composite files directly High-quality screening technology, reducing moiré patterns Dot-gain calibration

ImagesettersTypesetting device used to output fully-paginated text and

graphic images at a high resolution onto photographic film, paper or plates

Output problems are likely to occur during the transmission of files from the RIP to the imagesetter

Uses laser technology to output the page or color separations on the selected medium

Manufactured by different companies and differ in speed, precision, resolution, screening technology, and media capability

Page Description Languages (PDLs)Serves as the interface between the page composition

workstation and the RIPFormat by which all the elements to be placed on the page,

their respective positions on the page, and the page’s position within the larger document are identified in a manner the output device can understand

Adobe PostScriptAdobe portable document format (PDF)Hewlett-Packard PCL (Printer Control Language)

Adobe PostScript and PDFPostScript

Describes the appearance of a page to an output device Interpreter receives PostScript page descriptions and translates

them into dot patterns for a printer or pixels for a display

PDF Based on the PostScript imaging model Preserves a page’s original layout, type fonts, and graphics as one

unit to electronic transfer and viewing Device-independent format- not specifically related to any

particular device, converts data without loss of information

PDF continuedAcrobat Distiller, Acrobat Exchange, Acrobat Catalog, Acrobat

ReaderSimple, compact, object-oriented filesProcess quickly, page-independent, self-containedCan be repurposed, downloaded Contains extended job ticket

Customer info, proofing directions, trapping, imposition and ripping parameters, finishing and shipping instructions

Review Questions5. List at least five forms of manipulation that are allowed by image

editors/image manipulation programs6. What is a raster image processor (RIP)? What is its major function?7. What is am imagesetter? What is its major function?8. What purpose does a page description language (PDL) serve?9. What is portable document format (PDF) and what are some of its

main advantages?10. What does it mean when a file format is defined as device-

independent?

File CompressionFiles should be reduced in size before being sent to printers

Lossless- no data is lost (PKZIP compression technology or zip files) Unzipping the file will decompress it (.ZIP Self-extracting are unzipped by opening (.EXE) Decompressed image is identical to original Preferred for images that are printed

Lossy- some data is lost (quantization, DPCM, and JPEG files) Most video compression technologies Eliminates redundant or unnecessary information

JPEG files Joint Photographic Experts Group International data compression standard for continuous-tone

digital still imagesOpen-system, cross-platform, cross-deviceContains bitmap information only and supports grayscale,

RGB, and CMYK color modelsShould only be used on final images, at maximum quality

setting

File FormatsTIFF or TIF- Tagged Image File Format

Lossless or JPEG compression, grayscale, CMYK, RGB, indexed color

TIFF/IT-P1- Tagged Image File Format for Image Technology Device-dependent format, Color Electronic Prepress Systems

(CEPS)

EPS- Encapsulated PostScript Stable and reliable file format

WMF- Windows Metafile and PICT- Mac Bitmapped and Object-Oriented images

File FormatsDCS 1.0 and DCS 2.0-Desktop Color

Separations EPS graphic file, bitmapped and object-oriented

The Photo CD Compressed photographic images on CD-ROM,

raster images

GIF- Graphics Interchange Format Raster images, up to 256 colors, data compression

File NamingAlpha-numeric characters, no symbolsNo space at beginningUniqueUse appropriate file extensions (.TIFF, .EPS

etc.)

Storage DevicesDisk Storage: hard, floppy, CD-ROM, DVDStorage TapeMemory CardsUSB Drives

Page CompositionFormats pages of text and graphics Gives more control over text flow, kerning, and

positioning of graphicsAllows importations of many graphic file

formatsPageMaker, QuarkXPress, InDesign

Review Questions11. What is the main difference between lossless and lossy

compression?12. Which type of compression technique is preferred for

images that are to be printed? Why?13. Name at least four of the commonly used file formats14. Why is it better to use a page composition program to lay

out material than a word-processing program?

Preflighting Orderly review of files to identify things that could cause problems at

the output or prepress stage Discussion of file format and preparation with the service bureau or

printer while the project is still in the design stage Problems with customer-furnished files:

Missing or incorrect fonts Missing or incorrect trapping File defined with incorrect color (RGB vs. CMYK) Scans supplied in wrong file format Graphics not linked Incorrectly defined or underdefined bleeds No laser proofs supplied Missing graphics Resolution too high or too low in customer-supplied scans

Preflighting ContinuedBegins with printing out color separations and composite

hard copies Can be referred to if problems occur

Graphics should be linked Original art should be included if linked files are noneditable

Outline software and fonts used, trapping requirements, print specifications, and other pertinent information

Font Format and ManagementPrinter should use same fonts used for original page

compositionPage will change if fonts are substituted

Document reflow Bad word or line breaks Loss of kerning and tracking

Include fonts in files given to printer

Turnaround Time and ProofingNature and complexity of a job determine turnaround timeReview number of proofs

Samples for customer and guidelines for press operators Made from digital files, generated from film, or run off on a proof

press Iris Proofs- produces four-color proofs from digital file Matchprints- produced from film that will create printing page Bluelines or Diazo Proofs- produced from imageset film Press Proofs- generated with a proof press that produces

photomechanical proofs Color Proofs- photographic or photomechanical proofing system

Digital Printing TechnologyComputer-to-plate (CTP)

Takes fully-paginated digital materials and exposes information to plates in platesetters or imagesetters without creating film intermediates

Long-run projects and short-run projects

Digital-to-paper Printing of images directly on the press from electronic files,

eliminating preparation of film, plates and ink Quick turnaround, flexibility, and cost-effective four-color short runs Also know as Totally Electronic Printing (TEP) Reimageable or no image carrier for transfer or ink-jet ink or toner to

paper, pixels (bitmapped images)

Review Questions15. What is preflighting and why is it so important in prepress

production? 16. List five of the most common recurring problems with customer-

furnished files17. What problems can occur if fonts are substituted in a final

document file?18. What are some of the ways in which prepress proofs are

generated?19. What is CTP?20. What are some of the advantages of totally electronic printing?