CMYK vs. RGB; print vs. web

There are two important color models to be aware of. Here is the briefest of explanations on a very complex topic. If all you ever do is print to your little desktop color inkjet, you can get by without knowing anything about color models, so you can skip this for now. It will be here when you need it.

CMYK

CMYK stands for Cyan (which is a blue), Magenta (which is sort of red/pink), Yellow, and a key color, which is usually black. With these four colors of ink, we can print many thousands of colors, which is why it's called a "four-color process." (Specialized print jobs can include extra colors of inks.)

The colors in CMYK are like our coloring crayons or paint boxes -- blue and yellow make green, etc. This is the model we've been using throughout this chapter because this is a printed book.

CYMK is the color model you'll use for projects that are going to be printed by a printing press onto something physical. Just about everything you ever see printed in a book, a magazine, a poster, on matchbox covers or cookie boxes has been printed with CMYK.

RGB

RGB stands for Red, Green, and Blue. RGB is what you see on your computer monitor, television, iPone, etc.

In RGB, if you mix red and green you get -- yellow. Really. Mix full-strength beams of colored light that are not reflected off of any physical object -- it is light that goes straight from the monitor into your eyes. If you mix all the colors together you get white, and if you delete all the colors, you get black.

Print vs. web color models

The important thing to remember about CMYK and RGB is this:

Use CMYK for projects that are to be printed.

Use RGB for anything that will be viewed on a screen.

If you're printing to an expensive digital color printer (instead of a four-color printing press), check with the press operator to see whether they want all colors in CMYK or RGB.

RGB makes smaller file sizes, and some techniques in Photoshop work only (or best and usually faster) in RGB. But switching back and forth from CMYK to RGB loses a little data each time, so it's best to work on your images in RGB and change them to CMYK as the last thing you do.

Because RGB works through light that goes straight into our eyes, the images on the screen are gorgeous and backlit with an astonishing range of colors. Unfortunately, when you switch to CMYK and then print that with ink on paper, you lose some of that brilliance and range. That's just what happens, so don't be too disappointed.

--The Non-Designer's Design & Type Books (Deluxe Edition), DESIGN PRINCIPLES, SEVEN: USING COLOR, Page 106-108