Definitions First:
RGB: Red, Green, Blue, that's what you see on your monitor right now. It is also the format of most non-commercial printers. Just because your printer has cmyk cartridges does not make it a cmyk press. this is also the format of digital cameras.
CMYK: Cyan, Magenta, Yellow and Black: This is the format of commercial printing presses.
A strange and horrible thing happens when in Photoshop (edit>convert to profile>Cmyk) This simple action seems harmless enough. You may see a slight change in colors on your monitor when this happens. Unfortunately what comes out of the press is a dull lifeless low contrast image.
In a nutshell you are converting the primary colors of RGB to CMYK. Some colors cannot be reproduced in CMYK. this is called out of gamut. they just don't convert over. Purples , greens some yellows. The dull and lifelessness of the images is because of the way that cmyk reproduces black. Theroetically C+M+Y= black. but on a press it just uses too much ink. So the black ink is added. Sounds good but a true rich black is actually: CMYK calibration values must be 50% Cyan (C), 40% Magenta (M), 40% Yellow (Y), and 100% Black (K). Notice the colors below:
Well if the black in the image is now just grayish the overall contrast is reduced and the images look terrible. Here is a partial fix for the problem: Go to curves. Pull down the black channel and bring in the curve one box to the left at the top and one box to the left at the bottom. This adjusts the contrast without changing the original color too much. Add a brightness/contrast layer and boost the brightness 10-20 on the image. lo and behold the contrast is resurrected. Check each image to make sure the final is good and get a printed proof to test the results.
Good luck and I hope this will make going to press a little easier for you and make your client happier with the end result.
3 comments:
Interesting man, I always thought it was the same, but now i know the difference. Thanks!
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