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• TOTAL INK COVERAGE:
no press-paper combination can handle four "wet" inks
applied one over another at 100 percent of each color: 400 percent coverage
is a "recipe for disaster" guaranteeing color contamination, plugged-up
images, etc.
• SWOP, therefore, specifies a total ink limit of 300 percent with only
color printing at 100 percent. In practice, the limit runs from about
260 to 330 percent, depending on requirements, printing process, and type
of paper.
• BLACK-CHANNEL GENERATION: i.e., how much black ink to use, depending on
color quality requirements, prepress image correction, etc. These adjustments
can made as part of image processing in Photoshop. Methods:
GCR (gray component replacement) replaces the image's neutral colorant
(C, Y, or M) with a percentage of black ink. Benefit: sharper, more stable
colors without excess coverage
UCA
(under color addition): replaces black ink in shadow areas with percentages
of C, Y, and M. Benefit: richer colors in low-key ("nighttime") images.
UCR
(under color removal): black substitution for the neutral colorant in
shadow areas only. Benefit: better detail in shadows that might otherwise
"plug up."
• DOT GAIN: the tendency of halftone dots to expand in size as the ink is
absorbed into the paper. Dot gain is higher on uncoated stocks than on coated stocks because uncoated
stocks are more absorbent. To "leave room" for dot gain, Photoshop can
scale back image characteristics by the amount of gain anticipated for
the press-paper-ink combination that will be used.
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