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Chapter 22. PRINT > Color reproduction basics

Color reproduction basics

A computer monitor displays additive colors by projecting red, green, and blue (RGB) light, whereas an offset press prints subtractive colors using CMYK or spot color inks. Obtaining good CMYK color reproduction on an offset press is a real art. The output image will resemble the on-screen image only if the monitor is carefully calibrated for that output device. Note: In this section we're discussing offset press output. For online imaging issues, see the next chapter!

Ask your print shop at the outset

As we said a second ago, color separating is an art. Start by asking your print shop the following questions so you'll be able to choose the correct scan resolution and settings in the Custom CMYK dialog box:

What lines-per-inch setting is going to be used on the press for my job? This will help you choose the appropriate scanning resolution.

What is the dot gain for my choice of paper stock on that press? Allowances for dot gain can be made using the Custom CMYK dialog box.

Which printing method will be used on press—UCR or GCR? GCR produces better color printing and is the default choice in the Custom CMYK dialog box. (GCR stands for Gray Component Replace ment, UCR stands for Undercolor Removal.)

What is the total ink limit and the black ink limit for the press? These values can also be adjusted in the Custom CMYK dialog box.

Note:Change the dot gain, GCR or UCR method, and ink limits before you convert your image from RGB Color mode to CMYK Color mode. If you change any of these values after conversion, you must convert the image back to RGB Color mode, readjust the values, then reconvert to CMYK Color mode.

In which file format should the file be saved? Ask the print shop what file format it needs.



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