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For a CRT, the gamma that relates brightness to voltage is usually in the range 2.35 to 2.55; video look-up tables in computers usually adjust the system gamma to the range 1.8 to 2.2, [1] which is in the region that makes a uniform encoding difference give approximately uniform perceptual brightness difference, as illustrated in the diagram at ...
The rg chromaticity space is used in computer vision applications, and shows the color of light (red, yellow, green, etc.), but not its intensity (dark, bright). LMS color space (long, medium, short), a perceptual color space based on the response functions of the cones in the retina of the eye. It is mostly used in psychophysical research.
Tone mapped high-dynamic-range (HDR) image of St. Kentigerns Roman Catholic Church in Blackpool, Lancashire, England, UK. Tone mapping is a technique used in image processing and computer graphics to map one set of colors to another to approximate the appearance of high-dynamic-range (HDR) images in a medium that has a more limited dynamic range.
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.
HSL (hue, saturation, lightness/luminance), also known as HLS or HSI (hue, saturation, intensity) is quite similar to HSV, with "lightness" replacing "brightness". The difference is that the brightness of a pure color is equal to the brightness of white, while the lightness of a pure color is equal to the lightness of a medium gray.
The "luminance contrast" is the ratio between the higher luminance, L H, and the lower luminance, L L, that define the feature to be detected.This ratio, often called contrast ratio, CR, (actually being a luminance ratio), is often used for high luminances and for specification of the contrast of electronic visual display devices.
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 ...
The HSV, or HSB, model describes colors in terms of hue, saturation, and value (brightness). Note that the range of values for each attribute is arbitrarily defined by various tools or standards. Be sure to determine the value ranges before attempting to interpret a value. Hue corresponds directly to the concept of hue in the Color Basics section.