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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; luma is the encoded video brightness signal, i.e., similar to the signal voltage ...
Fig. 1. HSL (a–d) and HSV (e–h). Above (a, e): cut-away 3D models of each. Below: two-dimensional plots showing two of a model's three parameters at once, holding the other constant: cylindrical shells (b, f) of constant saturation, in this case the outside surface of each cylinder; horizontal cross-sections (c, g) of constant HSL lightness or HSV value, in this case the slices halfway ...
HSL (hue, saturation, lightness or luminance), also known as HSI (hue, saturation, intensity) or HSD (hue, saturation, darkness), is quite similar to HSV, with "lightness" replacing "brightness". The difference is that a perfectly light color in HSL is pure white; but a perfectly bright color in HSV is analogous to shining a white light on a ...
In a similar vein, the term luminance and the symbol Y are often used erroneously to refer to luma, which is denoted with the symbol Y'. The luma (Y') of video engineering deviates from the luminance (Y) of color science (as defined by CIE). Luma is formed as the weighted sum of gamma-corrected (tristimulus) RGB components.
The eye has different responses as a function of wavelength when it is adapted to light conditions (photopic vision) and dark conditions (scotopic vision). Photometry is typically based on the eye's photopic response, and so photometric measurements may not accurately indicate the perceived brightness of sources in dim lighting conditions where ...
Mathematically, for the spectral power distribution of a radiant exitance or irradiance one may write: =where M(λ) is the spectral irradiance (or exitance) of the light (SI units: W/m 2 = kg·m −1 ·s −3); Φ is the radiant flux of the source (SI unit: watt, W); A is the area over which the radiant flux is integrated (SI unit: square meter, m 2); and λ is the wavelength (SI unit: meter, m).
Luminance HDR/QtPfsGui is a free (open-source) HDR-workflow software for Linux, Windows and Mac OS X based around the pfstools package; LDR tonemapping is a free (open-source) tonemapper for low dynamic range images (a.k.a. "pseudo-HDR") Atlas is a free (open-source) port of the pfstmo tone mapping operators to Adobe After Effects
Luminance (Y or L v,Ω) The radiance weighted by the effect of each wavelength on a typical human observer, measured in SI units in candela per square meter (cd/m 2). Often the term luminance is used for the relative luminance, Y/Y n, where Y n is the luminance of the reference white point. Colorfulness