Out of Gamut

Image shows circle with CMYK color inside a larger RGB color circle.
Gamut is relatively easy to comprehend.

Definition: The phrase "out of gamut" refers to a range of colors that cannot be reproduced within the CMYK color space used for commercial printing. Graphics software is designed to work with images in the RGB color space throughout the editing process. The RGB color space has a much wider range of discernible colors than CMYK which explains why RGB colors tend to darken when moved to CMYK. When you print an image it must be reproduced with inks and these inks cannot reproduce the same range of colors that we can see with our eyes because the RGB color space uses light, not pigment, to produce the color..

Because the gamut of color that can be reproduced with ink is much smaller than what we can see, any color that cannot be reproduced with ink is referred to as "out of gamut." In graphics software, you often will see an out of gamut warning when you select colors that will shift when an image is converted from the RGB color space used in the editing process, to the CMYK space used for commercial printing.

The above image gives you a rather graphic view of understanding gamut. The outer box is all of the color known to modern man, including all of the colors we can see and those we can't , such as Ultra violet and Infrared.

The first circle is the 16 million colors found in the RGB color palette and the inner circle is all of the color that can be reproduced by a printing press. That dot in the midle, for all intents and purposes, is a black hole. If you move from a corner of the box to the dot, colors essentially get darker.

They get lighter as you move away.

If you pick a color in the RGB gamut, it will have an equivalent in the CMYK gamut but, with a difference. If a color moves toward that dot it gets darker.

Updated by Tom Green

Graphics Glossary