What is that crazy CMYK thing you keep mentioning?

This is a question I’m asked at least once a week: what is CMYK?


The difference between CMYK and RGB is an issue that designers are very familiar with.  When displayed on a monitor, graphics use a 3-channel system to display a color made up of Red, Green, and Blue.  However, when we send documents to print, a printer uses a 4-channel system called CMYK, which stands for Cyan, Magenta, Yellow, and Black.  Some systems even use six colors, CcMmYK, which add a lower-case ‘c’ and ‘m’ which stand for Light Cyan and Light Magenta, respectively.  There’s even an option to add a secondary black for some printers, known as pK (or Photo Black) or pantone inks (specific, standardized one-color inks).

So why the difference?  RGB is an additive color system, so in order to create a color (yellow, for example) your monitor activates green and red pixels.  You’ve no doubt seen this system at work before if you’ve ever been to a high school theater.  The spotlights above a stage have color filters over them, and to cast a yellow light on a stage the red and green lights would all be lit (or to create white light, all the lights are lit).

However, CMYK is a subtractive color system.  When light strikes a piece of paper, that paper absorbs light of certain wavelengths and what you see is the light that isn’t absorbed.  Thus, when you see yellow on a page, that page is absorbing (subtracting) all the light except that yellow.  While the Cyan, Magenta, and Yellow can be combined to make a semi-accurate black, the fourth channel of Black (k, or true black) is used for a more-accurate levels of deep dark colors.

Working between the two color systems is a necessary skill for graphic artists, who these days work digitally but still often print materials for use.  Understanding the effects of the two different color systems can have on your work is a huge part of doing accurate work.  Generally, you can send a document to print in an RGB color format (every home printer is designed to accept it), but it typically ends up darker than it appears on the screen.  This makes accurately designing graphics packages for companies difficult when they’re looking for both digital and print designs for branding unless your graphic designer understands how to correctly adjust color profiles for use in both web and print.

Thanks for reading!

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