The human eye is often able to detect many more colors than digital devices can reproduce. For instance, if you look at a blank, white page of paper, your eye is probably detecting at least 100 distinct shades of white. A white wall can easily have 1500 shades of white.
High-quality digital cameras, scanners, and other image acquisition devices can also detect hundreds of thousands or even millions of colors. Because of the presence of so many detectable colors, imaging professionals have invented models for specifying colors. These models are called color spaces.
The reason these models are referred to as color spaces is that most of them can be mapped into a 2-D, 3-D, or 4-D coordinate system similar to a Cartesian coordinate system. Hence colors can be said to be composed of coordinates in a 2-D, 3-D, or 4-D space. The color components in a color space are also referred to as color channels.
Some color spaces are intended to be independent of any device that is used to produce color images. Some are very device dependent. Both device-dependent and device-independent color spaces are discussed in the following sections: