CIE Lab Color Space

CIE L*a*b* color space

Here you have a simplified 3D model of the CIE L*a*b* color space.

One color - three numbers

In the CIE L*a*b* color space you define one color with three values L*, a*, and b*

Cyan sample

L*  55

a*  -37

b*  -50 

Lightness (L*)
The L* tells how light or dark the color is. The values are always ranging from 0-100. Black is 0 and 100 is white.

On each level the lightness is the same in all colors

Chroma (a* and b*)

The system of coordinates with the two axes a* and b* tells where the color is chromatically placed.

In the middle of the diagram, the values are 0 in both a* and b*. From there you go plux or minus - in both axes.

The range of a* and b* never exceeds -100 to 100 in the cmyk color space. In other color spaces the values can be higher.

The six-sided area in the target for paper type 2 (white backing) according to the ISO standard.

The diagram does not show the L* values.

A view -  without L*

The diagram is a simplified view. The colors are not accurate and the L* values are not shown.

The full color space is a three dimensional model and the diagram only shows two dimensions. If you wish to see all colors in the correct position, it would dmand 101 levels of L* (0-100).

On the left-hand side the simplified model.

On the right-hand side all colors are L* 47. On this level you only see the red color in correct position. The other five corner stones of cmyk are placed on other levels of L*.

The compromise is to have a simple diagram showing the chromatic placement - without L*.

source: cmykguide.com