Search results
Results From The WOW.Com Content Network
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]
RGB values of example colors with the same relative luminance as the lightest primary color (green) using BT. 709 primaries for ' (gamma correction) = 2.2 Luma is the weighted sum of gamma-compressed R′G′B′ components of a color video—the prime symbols ′ denote gamma compression .
The first three numbers are the white point to use, then the average surround lighting, in this case 200 cd/m², then the relative luminance of the surround on the same scale as the white point, in this case 18%, then the surround conditions, where 1 = average, 2 = dim and 3 = dark, and then XYZ coordinates of the color to check.
A typical computer display emits between 50 and 300 cd/m 2. The sun has a luminance of about 1.6 × 10 9 cd/m 2 at noon. [3] Luminance is invariant in geometric optics. [4] This means that for an ideal optical system, the luminance at the output is the same as the input luminance.
Example: A surface with a luminance of say 100 cd/m 2 (= 100 nits, typical PC monitor) will, if it is a perfect Lambert emitter, have a luminous emittance of 100π lm/m 2. If its area is 0.1 m 2 (~19" monitor) then the total light emitted, or luminous flux, would thus be 31.4 lm.
"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]
On a typical standard 2.2-gamma CRT display, an input intensity RGB value of (0.5, 0.5, 0.5) only outputs about 22% of full brightness (1.0, 1.0, 1.0), instead of 50%. [19] To obtain the correct response, a gamma correction is used in encoding the image data, and possibly further corrections as part of the color calibration process of the device.
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).