This article examines the benefits of color management and uses an actual job to demonstrate how color can be controlled.
Profiles A profile is a list of builds and the L*a*b* values of the colors those builds produced. Most profiles are created using black, cyan, magenta, and yellow, but this isn't a barrier in the world of screen printing. If you want a duotone profile, then make a two-color target and print it. If you want to incorporate orange or green or some corporate spot color into your images, then make the color target and print it. There is screen-printing magic to be had in the creative use of profiles.
Builds A build is the dot percentages of black, cyan, magenta, and yellow that go into producing a printed color. A build (for example, 80% magenta and 90% yellow to produce a red) does not accurately communicate a color. When one says 80% magenta and 90% yellow, is the result rhodamine or rubine? At what solid density? Builds are device dependent. The input profile is the standard that converts a device-dependent build into a device-independent L*a*b*.
Undercolor removal (UCR) UCR keeps dark colors from using too much ink and turning into mud. UCR is applied in the output profile and uses a curve to pull back color smoothly as it approaches a defined limit, usually found through painful experience. A job will land on your doorstep that involves a dark blue velvet blanket in a shadow. Without color management, that image will have areas with three or more overprinting solids. You will hit your total color limit and dark shadows will start changing color unpredictably.
Gray component replacement (GCR) GCR makes an image easier to print. Cyan, magenta, and yellow are replaced with black not just where the image is black, but also in dark colors without changing the color of the image. Black control is much more accurate when applied by an output profile than when done in Photoshop. For digital printing, medium black replacement should begin at around a 40% tone. Use maximum GCR for screen printing, but reduce the black width to around 95% to soften light tones. These lessons can be learned by screen printing images that are neutral in nature, such as silvery screws and bolts arranged on a shiny steel surface. Don't try to screen print big areas of light neutral colors without heavy GCR.
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