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The two major parts of the model are its chromatic adaptation transform, CIECAT02, and its equations for calculating mathematical correlates for the six technically defined dimensions of color appearance: brightness , lightness, colorfulness, chroma, saturation, and hue. Brightness is the subjective appearance of how bright an object appears ...
The CIE 1924 photopic V(λ) luminosity function, [cie 3] which is included in the CIE 1931 color-matching functions as the y (λ) function, has long been acknowledged to underestimate the contribution of the blue end of the spectrum to perceived luminance.
The latter is often simplified as a single value measured at e.g. 50% saturation level, implying a linear approximation of the not perfectly linear photo response non-linearity (PRNL). [2] Often PRNU as defined above is subdivided in pure "(offset) FPN" which is the part not dependent on temperature and integration time, and the integration ...
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 ...
Chromaticity consists of two independent parameters, often specified as hue (h) and colorfulness (s), where the latter is alternatively called saturation, chroma, intensity, [1] or excitation purity. [ 2 ] [ 3 ] This number of parameters follows from trichromacy of vision of most humans, which is assumed by most models in color science .
HSV (hue, saturation, value), also known as HSB (hue, saturation, brightness) is often used by artists because it is often more natural to think about a color in terms of hue and saturation than in terms of additive or subtractive color components. HSV is a transformation of an RGB color space, and its components and colorimetry are relative to ...
The difference between brightness and lightness is that the brightness is the intensity of the object independent of the light source. Lightness is the brightness of the object in respect to the light reflecting on it. This is important because the Helmholtz–Kohlrausch effect is a measure of the ratio between the two. [3]
To model the latter effect, in CIECAM97C the formula for J is adjusted as follows: J HK = J + (100 – J) (C / 300) |sin( 1 / 2 h – 45°)|, where C is the chroma and h the hue angle Q is then calculated from J HK instead of from J. This formula has the effect of pulling up the lightness and brightness of coloured samples.