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Relative luminance follows the photometric definition of luminance including spectral weighting for human vision, but while luminance is a measure of light in units such as /, relative luminance values are normalized as 0.0 to 1.0 (or 1 to 100), with 1.0 (or 100) being a theoretical perfect reflector of 100% reference white. [1]
For the RGB model, this is represented by a cube using non-negative values within a 0–1 range, assigning black to the origin at the vertex (0, 0, 0), and with increasing intensity values running along the three axes up to white at the vertex (1, 1, 1), diagonally opposite black.
RGB values of example colors with the same relative luminance as the darkest primary color (blue) using BT. 709 primaries for gamma correction equal to 2.2. For digital formats following CCIR 601 (i.e. most digital standard definition formats), luma is calculated with this formula:
"HCL" designed in 2005 by Sarifuddin and Missaou, which is a transformation of whatever type of RGB color space is in use. [5] HCT with tone as a synonym for luminance is then used within Material Design for its color system, using value ranges of 0–360°, 0–120+ and 0–100%, respectively. [6]
In fact, when Y′CbCr is designed ideally, the values of K B and K R are derived from the precise specification of the RGB color primary signals, so that the luma (Y′) signal corresponds as closely as possible to a gamma-adjusted measurement of luminance (typically based on the CIE 1931 measurements of the response of the human visual system ...
A comparison between a typical normalized M cone's spectral sensitivity and the CIE 1931 luminosity function for a standard observer in photopic vision. In the CIE 1931 model, Y is the luminance, Z is quasi-equal to blue (of CIE RGB), and X is a mix of the three CIE RGB curves chosen to be nonnegative (see § Definition of the CIE XYZ color space).
"Luminance" can mean several things even within the context of video and imaging: luminance is the photometric brightness of an object (in units of cd/m 2), taking into account the wavelength-dependent sensitivity of the human eye (the photopic curve); relative luminance is the luminance relative to a white level, used in a color-space encoding;
In order to convert RGB or CMYK values to or from L*a*b*, the RGB or CMYK data must be linearized relative to light. The reference illuminant of the RGB or CMYK data must be known, as well as the RGB primary coordinates or the CMYK printer's reference data in the form of a color lookup table (CLUT).