Posted on January 25, 2010 - by Lisa Nalewak
This is the 3rd in a series of articles on Graphic Design specifically written for Business Professionals.
CMYK stands for “Cyan, Magenta, Yellow and Black”, and CMYK color – sometimes referred to as “4-color process” or “process” color – is used specifically to produce full-color graphic materials and photographs on a “4-color” printing press. The “4” refers to the number of inks used (cyan, magenta, yellow and black) and “process” refers to a special printing technique that recreates the full spectrum of visible colors using just these four ink colors.
A graphic or photograph that was printed using CMYK color is made up of thousands of overlapping little dots of ink that the press puts down on paper as the paper passes through it. And – yup, you guessed it – those dots are cyan, magenta, yellow and black in color. The angle and density of these different colored dots relative to each other, and the diameter of the dots themselves, affect the color being displayed in a particular part of a printed document.
For example, large yellow and cyan dots placed together without any magenta or black dots nearby will make that part of a document look green. Large magenta and cyan dots with no other colored dots nearby will produce a purple or dark blue. Large dots of all four colors placed together will create a very dark, rich black.
The size of the dots, both in actual dimension and in relation to one another, will change the saturation and hue of the color. For example, using our green example above, if the yellow dots are larger than the cyan dots, the green will look more yellow, or “lime-colored”. If the cyan dots are larger than the yellow dots, the green will look more blue, or “kelly-green”. If the dots are small and let a lot of the background (in this case, white paper) show through, the color will be lighter. If the dots are larger and don’t let as much white show through, the color will be “brighter”, or “darker”. By adjusting the size of each dot relative to the other and the size of the dot to allow more or less of the background show through, you can recreate any color from a light lime yellow to a dark green-blue, and everything in-between. If you add a black dot nearby, adjusting its size and its density relative to the yellow and blue dots will allow you to make the color darker or lighter. If you add magenta, you’ll start to move the color towards any other number of colors depending again on the number of magenta dots relative to the yellow, blue and black dots, and the size of the magenta dot relative to the yellow, blue and black dots.
The graphic below is a good visual explanation of how 4-color process printing works to achieve different color results.
In essence, 4-color process printing uses the same color principles you learned as a kid in art class. Just like mixing the primary colors (red, blue and yellow) on an artist’s palette allowed you to create an entire spectrum of other colors to fingerpaint with, “mixing” our 4 “primary” printing ink colors (or adjusting the size, angle and relative density of each of the 4 colored dots throughout a document) allows a printing press to recreate a good portion of the visible color spectrum, and produce a “full-color” image.
When graphic designers create graphics meant to be printed in full-color – like for brochures, catalogues, magazines, and even for full-color logos or business cards – they “set” the colors for the graphics they create as “CMYK”. This way, when a printing press outputs these files as printed materials, it understands the right density and sizes for each of the four colored dots throughout the document in order to achieve the final desired result.
Some computer programs are able to display CMYK format color graphics on your computer monitor, even though you know (if you read my previous post on RGB color) that monitors use RGB (Red, Green Blue) as their color format instead of CMYK. These programs come with a conversion utility that allows the program to tell your monitor what the appropriate RGB color is for the CMYK colors defined in the graphic, and it’ll display the RGB colors instead. Some programs aren’t able to do this. Web browsers and browser based email applications generally aren’t able to display CMYK graphics at all.
What does this mean to me?
So what things do you need to keep in mind about CMYK color that’ll make your life easier when you purchase design services or printing services, or need to use or modify art you already have on file?
1) The vast majority of full-color, commercial printing equipment use CMYK format color. As a result, PRINTING PRESSES CAN NOT PRINT ARTWORK SET UP IN RGB COLOR. Printing presses have no idea what RGB color is. You may as well stand next to a printing press and try to verbally describe the colors to it yourself for all the good RGB artwork will do you. You must make sure that any artwork you send to a press that is to be printed in full-color is set up in CMYK mode, unless specifically told otherwise by the printer. (I’ll cover other types of full-color printing that use RGB in a later post).
2) You should NOT use CMYK art set up for printing in any document you’re creating to be displayed on an electronic device (PowerPoint slides, web graphics, etc.) If you’ve ever been sent a photo attached to an email that showed up as a little red X that you were unable to view, chances are the photo was in CMYK color, and your monitor or TV couldn’t display it because it was missing the RGB color information it needed to do so. TVs and monitors are as confused by CMYK as much as printing presses are confused by RGB.
3) CMYK COLORS LOOK DIFFERENT PRINTED ON PAPER THAN WHEN VIEWED ON A COMPUTER SCREEN. When an able computer application automatically converts CMYK art you are viewing to its RGB equivalent in order to display it on your monitor, the colors will look different than they do in print. In some cases, the color variation will be very noticeable (blues and purples translate the poorest from CMYK to RGB colors). In other cases it’s not as noticeable. It is imperative that you PRINT OUT AND PROOF CMYK ARTWORK on a color laser jet or inkjet printer in order to get a better approximation of the colors as they will appear when printed using a CMYK press. DO NOT RELY ON YOUR COMPUTER SCREEN to proof printed color. I should really repeat this as point #4, too, because it is a very important thing to remember. It’s an extremely common mistake people make unknowingly, and then wonder why their printed materials don’t look the way the expect them to look when they get them back from the press.
How to handle CMYK artwork for electronic display
Yes, this paragraph is a repeat of the one from my RGB post, but I’ll say it again: A good designer will ask you how you plan to use the art they are creating for you, and then will deliver you the art in multiple file formats and in multiple color formats that are matched as closely as possible. In this way, they assure that you have the art you need for any application, whether it’s print or electronic so you don’t experience color surprises down the road.
If you have CMYK artwork that you need to display electronically and you don’t have it in RGB format, a knowledgeable designer will be able to convert your CMYK file to RGB for you. Easier than converting from RGB to CMYK, converting from CMYK to RGB can sometimes still require color rebalancing for a “true” color match. The graphic quality of the art you give your designer will also affect the outcome. Higher resolution images generally give better color conversion results.