Understanding CMYK and RGB for Print - VP Associations

A brief guide to converting print files to CMYK

For many years, I have encouraged people to not only supply design files in CMYK format, but to do any color editing in CMYK mode. I have since learned the power of RGB!

What exactly is CMYK and RGB?

• CMYK refers to the four inks used in some color printing: cyan, magenta, yellow, and key (black); The key color is generally the first color printed. The lighter colors are then laid down and registered to the key color.
• RGB refers to the three colors of light used on a computer display: red, green, and blue. These colors can be combined in various proportions to obtain any color in the visible spectrum.

Digital cameras take pictures in RGB and, typically, images downloaded from the web will be in RGB. Your image will never have more actual color information than in its raw form before it is converted to CMYK for printed work. It’s worth the effort to learn different ways in which to modify the color of your images prior to converting them to CMYK.

There are three main color models for RGB:

1. sRGB, has been the industry standard in digital display and multi-media applications.
2. The next RGB color model: ADOBE 1998 contains more color than sRGB. Therefore it makes sense to do your color editing with this version. Recently, the world wide web began accepting images saved with this color model.
3. Pro Photo RGB has such a wide gamut of colors that a good portion of the color cannot be seen with the human eye. Also, much of it cannot be achieved when printing an image onto a substrate such as paper, even if it’s a coated sheet or in a printer with 12 inks!

So just like the three bears, the middle choice is what I recommend as being just right.

Great, how do I do that?

In Photoshop, under Edit, you’ll find Color Settings. This is the master template that Photoshop uses when you convert from CMYK to RGB, or vice versa, using Auto Color, Auto Tone, etc. Changing something here will not affect images on your computer; rather, it tells Photoshop what kind of color space you want to work in. In the case of converting an RGB image to CMYK, the program needs to know what to do with all the color data that can’t be crammed into the very small CMYK color gamut.

This can get pretty technical so feel free to call or email our Pre-Press team anytime!

Article written by:

Ken Kingsley

Prepress Manager