CIELCHuv

CIELCHuv is a cylindrical representation of the CIE Luv (CIELUV) color space. It expresses color using lightness, chroma, and hue, rather than the Cartesian u and v coordinates of CIELUV. In CIELCHuv, L remains the lightness component identical to CIELUV, while the chromatic components derive from u and v as C = sqrt(u^2 + v^2) and h = atan2(v, u) (in degrees, typically adjusted to the range 0–360).

From the CIELUV definition, u and v are functions of the tristimulus values X, Y, Z and a reference white; thus CIELCHuv encodes the same color information in a cylindrical coordinate system. To convert back, u = C cos(h), v = C sin(h) with h in radians, and L remains as before. The resulting L, C, h correspond to a color in the CIELUV space.

Typical ranges: L is approximately 0 to 100; C is nonnegative; h spans 0 to 360 degrees. CIELCHuv is commonly used in color design and processing tools because varying hue and lightness independently can be more intuitive than adjusting u and v directly, and it helps maintain perceptual consistency of hue across lightness changes in many regions.

Limitations: CIELCHuv is not perfectly perceptually uniform; equal changes in C or h do not translate to equal perceptual differences everywhere, and device limitations and the white point affect accuracy. It is one of several LCH representations derived from CIELUV, alongside CIELCHab and other variants.