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The CIELCh color space is a CIELab cube color space, whereby instead of Cartesian coordinates a, b, the cylindrical coordinates C (chroma, relative saturation) and h° (hue angle, angle of the hue in the CIELab color wheel) are specified. The CIELab - brightness L remains unchanged.
The CIELCh color space is not the same as the HSV, HSL or HSB color spaces. Although their values can also be interpreted as a base color, brightness and saturation of a color tone, and are polar coordinate transformation of what is technically defined RGB cube color space, CIELCh is still perceptually uniform.
For example, H and h are not identical, because HSL space use as primary colors, the three additive primary colors red, green, blue (H = 0, 120, 240°), instead the CIELCh system use four physiological elementary colors yellow, green, blue and red (h = 90, 180, 270, 360°). h = 0 mean the achromatic colors to the gray axis.
There are simplified spellings LCh, LCH and HLC common.