The CIELab system is derived from Adams's (1942) system, the colour difference formula being a cube root version of the AdamsNickerson formula. The colour difference formula developed by Adams is usually referred to as the AdamsNickerson colour difference formula due to the work of Nickerson (1947,1950) which led to the successful introduction of the formula in industrial applications. The rectangular coordinates L*,a*,b* of this system are calculated from the CIE X,Y,Z tristimulus values by equations.
Lightness forms the central axis of the system with the a and b axes perpendicular to the lightness axis and each other. Planes of constant lightness form ab chromaticity planes.
