CAM02UCS

CAM02UCS, short for CAM02 Uniform Color Space, is a perceptually uniform color space derived from the CIECAM02 color appearance model. It was developed to provide a three-dimensional space in which Euclidean distances between color samples approximate perceived differences more closely than many other color representations. By mapping CAM02 outputs into a uniform space, small color changes become more consistently representable across the color gamut, aiding tasks such as color difference measurement, color matching, and quantization.

The CAM02UCS framework uses the appearance attributes produced by CIECAM02—primarily lightness, chroma, and hue—and re-encodes them into a Cartesian coordinate system. In CAM02UCS, a lightness-like coordinate J' is derived from the CAM02 lightness J through a non-linear transformation that better reflects perceptual brightness. The chroma and hue components are combined into planar coordinates a' and b' (often expressed as a' = C' cos(h') and b' = C' sin(h')), where C' and h' encode the chroma and hue information. The resulting J', a', b' triplet forms a uniform space in which equal distances correspond, as far as possible, to equal perceptual differences.

CAM02UCS is related to but distinct from other uniform color spaces such as CIELAB and CAM16-UCS. It relies on the CAM02 appearance model, making it compatible with viewing conditions and adaptation assumptions embedded in CAM02. It is used in color science research and in image processing workflows that require reliable perceptual color difference measurements.