Labkleurruimte

Labkleurruimte, often referred to as CIELAB or the Lab color space, is a model for representing colors in a way that approximates perceptual differences for human vision. It is a device-independent color space designed by the International Commission on Illumination (CIE) and is derived from the CIE XYZ tristimulus values under a specified reference white.

A color in Lab is specified by three coordinates: L*, a*, and b*. L* denotes lightness, ranging roughly from 0 (black) to 100 (white). The a* axis runs from green (negative) to red (positive), and the b* axis runs from blue (negative) to yellow (positive).

Lab is not a simple encoding for devices; it is intended to reflect perceptual differences as uniformly as possible. Colors are computed from XYZ using a nonlinear transformation, with a fixed reference white such as daylight. Equal changes in Delta E in Lab are used to judge perceptual difference.

Common uses include color management in printing, textile and paint industries, digital image processing, color difference measurement, and quality control. Delta E values in Lab quantify color accuracy and tolerance.

Limitations include dependence on the viewing conditions that define the reference white, and imperfect perceptual uniformity across all colors and luminances. For some tasks, alternative spaces or models, such as CIECAM02, may be preferred.

In Dutch usage, Labkleurruimte is the usual term for this color space and is often contrasted with device-dependent spaces like RGB or CMYK.