Commercial Printing Processes

TPC November 2001

Barbara Manning

AgendaNine types of

commercial printing processes

Offset LithographyColor theory --

additive and subtractive color

Pre press, halftone screens and film stripping

Nine Printing ProcessesOffset lithography

type is offset from the printing plate to a blanket then to the paper.

Engraving ink wells shaped like the type transfer image

direct to the paper -- ink surface is raised off the paper

Thermography treated inks, heat dried to rise (like bread) from

the paper surface

Printing processes

Reprographics copying or duplicating (Xerox or Kinko’s)

Digital printing printing direct from computer files (Giclée, IRIS

continuous tone printing)

Silk screen ink is pressed through a sieve onto many surfaces

Printing processesLetterpress

relief image metal plates are inked and pressed into the paper

Flexography relief image photopolymer plates are inked and

pressed into paper

Gravure volatile inks are sucked from ink wells at high

speeds

Offset LithographyBased on the principle that ink and water

don’t mix. Images are photographically reproduced on

printing plates which are dampened first with water, then with ink.

Ink adheres to the image area, the water to the non-image area

The image is transferred to a rubber blanket (offset) and then to the paper.

Offset lithography

Offset web press

Reproducing ColorThree essential elements to seeing color:

Light, an illuminated object and an observer At low light levels colors look different

• why fire trucks are no longer painted red In bright daylight we can see more colors, more

contrast and more saturation The color spectrum shows the range of color

visible to the human eye.• White light is a mixture of all the visible colors

• It’s called Additive Color

Additive ColorThe visible spectrum

Used in monitors.

Primary Colors are Red, Blue and Green

When combined it produces ‘white’ light or the combination of all visible colors.

Additive colorPrimary Colors are Red, Blue and Green

When combined it produces ‘white’ light or the presence in equal strengths of all the colors.

Subtractive color complements additive color

Subtractive ColorCombines pigments that absorb or filter light.

Used in any pigment (ink, colored pencils, crayons) on a substrate

Primary colors are Cyan, Magenta and Yellow

Combined they produce ‘black’ or the absence of color.

Complementary Color

Additive Colors

SubtractiveColors

(also the primary printing colors)

Additive & Subtractive RelationshipIt’s Complementary!

Place additive primaries at the points of the triangle. Subtractive primaries are placed between the two additives that combine to create them

A subtractive color filters out the primary color across from it (the complement) from white light.

Subtractive Colors act as a filter

The ink on the paper absorbs blue, reflecting green and red light which you see as yellow.

The ink on the paper absorbs blue, reflecting green see as green.

Hue, Value and SaturationHue is identified as the color family or color

name (such as red, green, purple). Hue is directly linked to the color's wavelength.

Saturation, also called "chroma," is a measure of the purity of a color or how sharp or dull the color appears.

Brightness, also called "luminance" or "value," is the shade (darkness) or tint (lightness) of a color.

Areas of an evenly colored object in direct light have higher brightness than

areas in shadow.

Hue, Value and Saturation

Halftone reproductionPrinting processes can only print ink or leave

blank areas on the page they cannot print different shades of a color

• A newspaper press can only print solid black or nothing.

Photographs are continuous tone, that is they contain various shades of gray between the extremes of black and white.

In order to overcome printing limitations the halftone process was invented.

Photographic Reproduction

Half tone reproduction

Preparing photographs for printing.

Halftone ReproductionThe traditional halftone

process converts different tones into dots of varying size.

The eye has limited resolving power and at a distance,(the distance from your eye to the magazine) is tricked into seeing these dots as continuous tone.

http://www.ted.photographer.org.uk/photoscience_halftones.htm#Colour Reporoduction

Halftone ReproductionBeware of

dot gain• dots gain size when transferred to the paper

moiré• screen angles are not correct for 4c printing

register• four colors are not EXACTLY aligned in inch thousanths

screen value• 250 lpi screen used when the press can’t handle it

picking• paper coating is picked off and transferred to other sheets

ink and water ratios• too much or too little of either ruins the job

press speed• too fast or too slow ruins the job

Knockout, mask, reverse & trap

Sources Print Glossary http://www.tcnj.edu/~print/pages/glossary.shtml

Offset Printing process: http://www.flashprinting.com/Printprocess.html http://www.howstuffworks.com/offset-printing2.htm

Giclée Digital Process http://www.fineartphotographic.com/printingprocess.htm

Kodak Digital Learning Center http://www.kodak.com/US/en/digital/dlc/index.jhtml

Capturing digital images http://www.kodak.com/US/en/digital/dlc/book3/chapter2/digColorM3_1.shtml

Color Theory http://www.kodak.com/US/en/digital/dlc/book3/chapter2/index.shtml

Visible Spectrum http://www.glenbrook.k12.il.us/gbssci/phys/Class/light/u12l2a.html

Four Color Process Printing http://www.printingforless.com/creativepro/perfectpiece.html

MS Publisher tips http://www.printingforless.com/creativepro/publishertips.html

Color Separation software http://www.fastfilms.com/

Halftone reproductionhttp://www.ted.photographer.org.uk/photoscience_halftones.htm

Hue, Value and Saturation http://www.colorcube.com/software/docss/docss.htm

http://www.geocities.com/~jlhagan/advanced/color_psychology2.htm

http://www.pantone.com/products/products.asp?idArticle=110&idArea=16

Sources