A Simple Explanation of Why CMYK Makes Sense for Printing

Have you ever wondered why magazine publishers and other printed material producers ask you to submit your images in CMYK color space instead of sRGB or Adobe RGB? If you haven’t thought much about the “why” before now, you might be interested in the tidbit of info in this video.

If you’re like me, you rarely think about changing your color space mode to anything other than sRGB. I don’t often have a reason to switch. After all, sRGB is what my print lab requires, and it’s what my monitor is calibrated for. But now and again, I am lucky enough to be asked to submit for magazine publication or I run into some special printing situation where the lab requires CMYK.

All talk of color space changes used to terrify me. I have spent hours studying different conversion techniques, the ups and downs of each choice, and in-depth material on which space is best and why. You can study for days about the differences in color spaces and the benefits of each, and if you are up for that, I recommend that you check out Jeff Rojas’s article here, Alex Ventura’s article here, and Zach Sutton’s article here.

On the other hand, if you want to check out a simple, concise, and rather eye-opening explanation on the difference between RGB and CMYK and why printed publications require one rather than the other, check out this quick video by the always-entertaining Unmesh Dinda of PiXimperfect. In it, you will learn the way numeric color values work together and where whites and blacks play into all of this. There are no bells and whistles here — just some straightforward information that you didn’t even know you wanted to know. Enjoy!

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He seems to have explained, in a round-about way, the difference between additive and subtractive color models. But this doesn’t seem to answer the question, “why CMYK?” Why, for example, why can’t we print with red, green, and blue inks? Wouldn’t adding rgb inks on paper also approach black as ink density increased and white as they decreased? If you have CMY pixels in a display, wouldn’t they also mix to white? These are harder, but also more interesting, questions to answer.

Zac Henderson's picture

I was thinking the same thing. Would have preferred him get into explaining why RGB on a screen = white and why CMYK in print = black.

Observations are great but knowing the principles in a bit more detail leads to greater understanding. Additive color mixing (RGB) = light wavelengths that combine to achieve pure white. Whereas Subtractive color mixing = physical reflective medium that, when combined, achieve black.

In additive color mixing (light), black is the lack of light and white is the combination of Red Green and Blue light.

In Subtractive color mixing, white can only be achieve with paper white while black is the combination of all pigment/ink.

Spy Black's picture

Even though I do work for print, I retouch in RGB. It's a problem when working with stuff like (for instance) emeralds that just die when you transfer to CMYK. I can salvage some of it by pull a luminosity mask in Lab, but it's always a losing battle. Artwork is a mixed bag. Products made with bright polymers are another disaster. I can go on, but most important is the client expectations. Too many see a great image in the photographer's studio in Adobe RGB on a decent monitor, and then start harping when they see the first press proofs. I have issues with studios that don't warn the client up front about gamut issues down the road with certain products if they're going to print.