The CIELAB colour model was defined in 1976 by the Commission Internationale de l’Eclairage and describes all perceptible colours. It is a further development of the Hunter-LAB colour scale from 1966 and a mathematical colour model in which the spectral properties of an object and the perceptual properties of our visual system are offset against each other. CIELAB, or LAB for short, has established itself to this day wherever exact colour calculation is required, whether in colour measurement, formulation or in common operating systems: Colour management usually works via CIELAB.
Hunter L, a, b and CIE 1976 L*a*b* (CIELAB) are both based on the theory of opponent colours. This theory assumes that the receptors of the human eye perceive colour as pairs of opposites. With LAB, these are three pairs:
– L-scale: Light vs. dark. A low number (0-50) stands for darkness and a high number (51-100) for lightness, 0 is absolute black, 100 is absolute white.
– a-scale: Red vs. green, a positive number represents red and a negative number represents green.
– b-scale: Yellow vs. blue, a positive number represents yellow and a negative number represents blue.
The L value indicates the ratio of light to dark, the a value the range from red to green and the b value the range from yellow to blue. All three values together can fully describe the colour of an object.