Design Nomenclature / Color
CIELAB
Also called Lab, L*a*b*, CIE L*a*b*, LCh, CIELCh
- Color
- Systems & Spec
- 2D & 3D
A device-independent opponent space — L* for lightness, a* green to red, b* blue to yellow — built so equal numeric distances approximate equal perceived differences. Its polar form, LCh, restates a* and b* as chroma and hue angle. Both inherit a documented flaw: the blue region bends, so hue drifts along a ramp that should hold it.
In practice
The reference space for print specification and Delta E tolerancing. Its hue non-uniformity in the blues is precisely what OKLab was built to repair.
Not to be confused with
- OKLabBjörn Ottosson's 2020 revision of the Lab approach, fitted to modern appearance data. It corrects CIELAB's blue-hue skew and its weak lightness prediction, so interpolation between two colors stays on a plausible hue and passes through a plausible middle instead of drifting purple or sagging grey.
- CIE XYZThe 1931 foundation space: three imaginary primaries derived from color-matching experiments and chosen so that Y carries luminance and every real color takes positive coordinates. Nothing here is designed for human use — it is the hub every other space converts through, and the reason a Lab value means the same thing on two continents.
- HSLA cylindrical remapping of RGB into hue, saturation, and lightness, with L running 0 to 100% and every fully saturated hue landing at L 50%. That is a fact about the geometry, not about perception: HSL yellow and HSL blue at L 50% differ enormously in the lightness anyone actually sees.