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The "CIELCh" or "CIEHLC" space is a color space based on CIELAB, which uses the polar coordinates C* (chroma, colorfulness of the color) and h° (hue angle, angle of the hue in the CIELAB color wheel) instead of the Cartesian coordinates a* and b*. The CIELAB lightness L* remains unchanged.
Lightness is a visual perception of the luminance of an object. It is often judged relative to a similarly lit object. In colorimetry and color appearance models, lightness is a prediction of how an illuminated color will appear to a standard observer. While luminance is a linear measurement of light, lightness is a linear prediction of the ...
CIELAB produces a color space that is more perceptually linear than other color spaces. Perceptually linear means that a change of the same amount in a color value should produce a change of about the same visual importance. CIELAB has almost entirely replaced an alternative related Lab color space called “Hunter Lab”. This space is ...
CIELAB L* is a CIE-defined achromatic lightness quantity (dependent solely on the perceptually achromatic luminance Y, but not the mixed-chromatic components X or Z, of the CIEXYZ colorspace from which the sRGB colorspace itself is derived), and it is plain that this appears similar in perceptual lightness to the original color image.
A color is fully specified by listing the three numbers for hue, value, and chroma in that order. For instance, a purple of medium lightness and fairly saturated would be 5P 5/10 with 5P meaning the color in the middle of the purple hue band, 5/ meaning medium value (lightness), and a chroma of 10 (see swatch).
HSL (hue, saturation, lightness/luminance), also known as HLS or HSI (hue, saturation, intensity) is quite similar to HSV, with "lightness" replacing "brightness". The difference is that the brightness of a pure color is equal to the brightness of white, while the lightness of a pure color is equal to the lightness of a medium gray.
50% CIELAB lightness ( Y = 18.4%) In photography , painting , and other visual arts, middle gray or middle grey is a tone that is perceptually about halfway between black and white on a lightness scale; [ 1 ] in photography and printing, it is typically defined as 18% reflectance in visible light.
A 2009 modification of CIELAB in the spirit of RLAB (with discounting-the-illuminant). Uses CIECAM02 chromatic adaptation matrix to fix the blue hue issue. [15] JzAzBz A 2017 UCS designed for HDR color. Has J (lightness) and two chromaticities. [16] XYB A family of UCS used in Guetzli and JPEG XL, with a main goal in compression. Better ...