A glossary of color, contrast, and vision terms
One of our bigger projects is the distillation of the last 4.5+ years of research and writing into manageable chunks, from the current scattered and disjoined repositories of information. Among the saddest here is the glossary, which is presently scattered across 4 or 5 sites and an unknown number of pages and posts.
This repo then is aimed to be the canonical collection pool of all things related to the terminology of color, contrast, vision, etc.
Roadmap: as of right now, this is just a set of markdown files, however, the intent is a database, with flags for "Basic Plain Language", with progressive enhancement to "Intermediate Color & Design" to "Expert Colorimetry" etc. As an example, the simplest, and then expanding definition of luminance:
- Luminance
$L$ — a physical measure of visible light intensity.
Works for most purposes. If we add in the weighting for spectral sensitivity, then we need to further clarify that lightness, darkness, and brightness are not part of that weighting.
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Luminance
$L$ — a physical measure of visible light intensity.- Luminance is measured from a surface, expressed as candela per square meter (cd·m²).
- Luminance is weighted per the spectral sensitivity of human vision.
- Luminance is mathematically linear, as is physical light.
- Therefore, Luminance is not proportional to the human visual perception of lightness, darkness, or brightness.
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Relative luminance
$Y$ is proportional to physical values of luminance.-
$Y$ is normalized to a range, such a 0 (black) to 100 (white). - The symbol
$Y$ relates to CIE 1931$XYZ$ and should not be confused with$Y^\prime$
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Luma
$Y^\prime$ (Y prime) is a gamma encoded signal, used in some broadcast video systems.
See also: https://cie.co.at/eilvterm/17-21-050 for the expert colorimetry version.