CMYK model

The colors you see on your monitor are reproduced on paper using pigments instead of light. Printers render colors on paper and other mediums through reflected light. The most common method of reproducing color images on paper is by combining cyan, magenta, yellow, and black pigments. These four colors are the color components of the CMYK (Cyan, Magenta, Yellow, and black) color model. Each color of the CMYK color model is described as a percentage (from 0 to 100). Pigments produce color by reflecting certain wavelengths of light while absorbing others. Darker pigments absorb more light. Because the CMYK color model is based on pigment colors, higher percentages of pigment result in darker colors. In theory, when 100 percent cyan, 100 percent magenta, and 100 percent yellow are combined, the resulting color is black. In reality, a muddy brown is produced so black pigment must be added to the color model and to the printing process, to compensate for the color limitations. The CMYK color model is called a subtractive color model because it creates colors by absorbing light. The CMYK model cannot be a color standard because its color results are not 100 percent repeatable as it is a device dependent color model.

The CMYK color model

The CMYK color model

CIE Lab model

A great deal of color research has been accomplished in order to acquire a color model that is device independent and repeatable. In 1931 La Commision Internationale de LEclairage (CIE) defined a device-independent color model, based on how the human eye perceives color. The CIE Lab model incorporates the theory that a color cannot be both green and red at the same time nor can it be yellow and blue at the same time. As such, single values are used to describe the green/red and blue/yellow components of any color. Lab stands for the three values this model uses to define color — a lightness value (L) which can range from 0 to 100 and two chromaticity ranges: green to red (a) and blue to yellow (b). The two chromaticity values can range from +120 to -120. Lab (sometimes called L*a*b*) provides a system for defining color that bases color values on widely accepted standards rather than on individual color-producing devices.

Reproducing colors accurately

Each piece of equipment you use, from scanners to printers, to create your project, has a specific range of colors that it can reproduce. This is referred to as a device gamut. If you don't take these differences into account, the colors you see on your monitor may not match the colors on the printed page. For more information, see "Reproducing colors accurately" on page 325.

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