CIELAB System

The CIELAB color space is the most common used color space in the industry. The vertical L*-axis reflects the lightness of a color. Here L*=0 represents absolute black, L*=100 represents perfect white. The positive a*-axis represents the red parts of a color, the negative a*-axis represents the green shares. The positive b*-axis is for the color yellow, negative b*-values mean blue. Thus in this three-dimensional structure you can „address“ all real existing colors at one light type, measurement geometry and standard observer.

Another way to display the a* and b*-axes is the representation in polar coordinates.
C* is named Chroma and shows the difference from the neutral gray axis to the sample.
H is called the Hue angle. It is always measured counter-clockwise starting from the positive a*-axis.

This set of definitions is mainly used for saturated colors, since values in numbers are easier to understand. For instance, the color orange is more saturated than the sample, not more red and more yellow. The difference from a sample to the standard is stated in delta values (Δ or d):
ΔL* =   0,5 sample is 0.5 units brighter
Δa* = -1,5 sample is -1.5 units greener
Δb* = -3,6 sample is -3.6 units bluer
ΔC* = -3,9 sample is -3.9 units less colored
ΔH   =  0,7 sample is 0.7 depends on the location