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An illuminant is characterized by its relative spectral power distribution (SPD). The white point of an illuminant is the chromaticity of a white object under the illuminant, and can be specified by chromaticity coordinates, such as the x, y coordinates on the CIE 1931 chromaticity diagram (hence the use of the relative SPD and not the absolute SPD, because the white point is only related to ...
A list of standardized illuminants, their CIE chromaticity coordinates (x,y) of a perfectly reflecting (or transmitting) diffuser, and their correlated color temperatures (CCTs) are given below.
The process of calculating the white point discards a great deal of information about the profile of the illuminant, and so although it is true that for every illuminant the exact white point can be calculated, it is not the case that knowing the white point of an image alone tells you a great deal about the illuminant that was used to record it.
For example, the white point of an sRGB display is an x, y chromaticity of (0.3127, 0.3290), where x and y coordinates are used in the xyY space. ( u′ , v′ ) , the chromaticity in CIELUV , is a fairly perceptually uniform presentation of the chromaticity as (another than in CIE 1931) planar Euclidean shape.
Image:Map of USA-bw.png – Black and white outlines for states, for the purposes of easy coloring of states. Image:BlankMap-USA-states.PNG – US states, grey and white style similar to Vardion's world maps. Image:Map of USA with county outlines.png – Grey and white map of USA with county outlines.
In addition, the SMPTE C RGB primaries used in North American standard definition are different than those of BT.709 (SMPTE C is commonly referred to as NTSC, however it is a different set of primaries and a different white point than the 1953 NTSC. [22]). The red and blue primaries for PAL and SECAM are the same as BT.709, with a change in the ...
Map of the USA showing borders of states and counties. Adapted by Wapcaplet from a public-domain map courtesy of the U.S. Census Bureau website. Date: 25 September 2006: Source: en:File:Map of USA with county outlines.png: Author
The chromaticity components U* and V* are defined such that the white point maps to the origin, as in Adams chromatic valence color spaces. This arrangement has the benefit of being able to express the loci of chromaticities with constant saturation simply as ( U *) 2 + ( V *) 2 = C for a constant C .