Does your print designer ever tell you “I’m prepping the files for print?” Do you ever wonder what that means, exactly? Part of what your designer is doing is making sure every image and every color in the file is set for CMYK (Cyan, Magenta, Yellow, Black) so that it prints true. Most images downloaded from the internet or from image stock houses arrive in RGB (Red, Green, Blue) color mode.
It is a common mistake to assume that the colors seen on the your computer screen will look the same when you print. The issue lies in the fact that the computer screen and most photo editing programs show colors in RGB mode, while images are printed on paper in Cyan-Magenta-Yellow-Black (CMYK) format. (Have you ever loaded your color ink jet printer with new ink? It sure doesn’t come with an RGB inkwell!) During the design and layout phase, most designers will convert the RGB images to CMYK in the process. But at the end of each design phase they must still go through and triple check!
So what is RGB versus CMYK?
RGB Color Mode
RGB is the color scheme that is associated with electronic displays, such as CRT, LCD monitors, digital cameras and scanners. It is an additive type of color mode, that combines the primary colors, red, green and blue, in various degrees to create a variety of different colors. When all three of the colors are combined and displayed to their full extent, the result is a pure white. When all three colors are combined to the lowest degree, or value, the result is black. The RGB scheme has a greater range of colors than CMYK and can produce colors that are more vivid and vibrant. These colors are beyond the range of CMYK to reproduce and will come out darker and more dull in print than what is seen on the monitor or display.
CMYK Color Mode
Printers print color onto paper using the CMYK color mode only. This is a four color mode that utilizes the colors cyan, magenta, yellow and black in various amounts to create all of the necessary colors when printing images. It is a subtractive process, which means that each additional unique color means more light is removed, or absorbed, to create colors. When the first three colors are added together, the result is not pure black, but rather a very dark brown. The K color, or black, is used to completely remove light from the printed picture, which is why the eye perceives the color as black.
So which one do I use, and when?
A good rule of thumb is anything dealing with the web should always be in RGB and printed material should be in CMYK.
Back in the printing press days, to achieve color, each ink (cyan, magenta, yellow, and black) had its own plate. First the printer would lay down one color, run the paper through, wait for it to dry, lay down another color, run that same paper through, wait for it to dry and so on. Printing presses still work on that same theory to this day with the exception that offset printers have a 4, 6, or 8 color press that runs each plate simultaneously. These printers also now utilize “spot” colors which is much like the paint swatches you get at your local hardware stores. You pick that color and that is the exact color you get. There is no mixing of C, M, Y and K to achieve it.
As the printing age has progressed, the digital printer has come a long way, allowing to print in RGB as well. But the standard still stays the same – use CMYK on all printing needs, as the color will appear differently if printed in RGB.
CMY without the K?
Remember art class as a kid? Did you ever take all the finger paint and smush it around the page all together? What color did you get? Brown.
When you mix C, M and Y, you end up getting a dirty brown color just like you did when you mixed all the finger paint. That’s why, in printing, a separate pure black plate is needed to get those dark rich colors. Click the image below to see more!
Why is Black referred to with a K?
The “K” in CMYK stands for “key” because in four-color printing, cyan, magenta, and yellow printing plates are carefully keyed, or aligned, with the key of the black key plate. The “key plate” is said to add the “detail” to a printed image. This is true in that the black plate in a four color process print pushes the contrast and creates “detail”.
While the term today may have adopted the meaning for the process of aligning plates, the term “key” does not originate from this process. The color “registration” is more closely related to the process of aligning plates. The term “key” originates from the rotary printing press in 1843 that had screw keys to control the amount of ink printing on a substrate. Offset presses also use this mechanism.