CMYK color

CMYK color is very different from RGB. It is based on the light-absorbing quality of ink on paper. When white light hits these inks, some visible wavelengths are absorbed while other wavelengths are reflected back to your eyes.

CMYK images are comprised of various percentages of only four colors of ink — cyan, magenta, yellow, and black. Darker colors have higher percentages, and lighter colors have lower percentages. These colors correspond to the inks used in the offset printing process that is used for professional, high-end printing of magazines, books, and sales and marketing materials. Full-color images that are printed on an offset press must be in the CMYK color mode.

Cyan, magenta, and yellow are called subtractive colors. That's because colors are produced by subtracting various percentages of cyan, magenta, and yellow from white. Technically, if you combined these three inks, you would produce black. But because of ink impurities, they create a nasty brown color. Therefore, K (or black) is added to produce black.

CMYK colors are also known as process colors. When all four inks are set to 0 percent, pure white is produced. A CMYK image contains four channels, one for each process color. The greater the number of channels, the larger the image. High-resolution, CMYK images are usually the behemoths of digital images.

Figure 3-5:

The red, green, and blue channels in an RGB image appear as grayscale images when viewed independently, but combine to produce a full-color image.

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