Colour location

The colour location describes the position of a measured or selected colour within a colour space. This is often defined by coordinates, e.g. using L, a and b in the CIELab colour space.
The set of all the colour locations in a colour space is called the colour gamut (or gamut).


HLC is an easy to understand representation of the CIELAB colour space. The CIELAB colour model was defined in 1976 by the Commission Internationale de l’Eclairage. It is 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-colours) has become generally accepted until today, wherever exact colour calculation is required, be it in colour measurement, formulation or in the common operating systems: Colour management usually works via CIELAB.

Instead of the rectangular coordinates for L, a and b the CIELAB polar coordinates HLC can be used.

Here, the vertical L-axis is identical.

The horizontal position of a colour location is determined here by the angle H to the positive a-axis (counter-clockwise and in the unit degree) and the radius C, the distance to the L-axis.

HLC, also LCh or LCH(ab), stands for
• Hue (colour tone [angle])
• Lightness (brightness)
• Chroma (saturation)

and is much easier to comprehend than the abstract a and b coordinates, for which hardly anyone can imagine the corresponding colour.

This text is taken from the freieFarbe e.V. CIELAB HLC Colour Atlas, which you can download here for free.

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