Relative luminance
Ratiometric definition of luminance / From Wikipedia, the free encyclopedia
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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] Like the photometric definition, it is related to the luminous flux density in a particular direction, which is radiant flux density weighted by the luminous efficiency function
of the CIE Standard Observer.
![]() | This article may be too technical for most readers to understand. (June 2020) |
The use of relative values is useful in color or appearance models that describe perception relative to the eye's adaptation state and a reference white. For example, in prepress for print media, the absolute luminance of light reflecting off the print depends on the specific illumination, but a color appearance model using relative luminance can predict the appearance by referencing the given light source.