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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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