The CIE 1960 color space ("CIE 1960 UCS", variously expanded ''Uniform Color Space'', ''Uniform Color Scale'', ''Uniform Chromaticity Scale'', ''Uniform Chromaticity Space'') is another name for the

chromaticity Chromaticity is an objective specification of the quality of a color regardless of its luminance. Chromaticity consists of two independent parameters, often specified as hue (h) and colorfulness (s), where the latter is alternatively called ...

space devised by David MacAdam. The CIE 1960 UCS does not define a

luminance Luminance is a photometric measure of the luminous intensity per unit area of light travelling in a given direction. It describes the amount of light that passes through, is emitted from, or is reflected from a particular area, and falls withi ...

lightness Lightness is a visual perception of the luminance (L) of an object. It is often judged relative to a similarly lit object. In colorimetry and color appearance models, lightness is a prediction of how an illuminated color will appear to a stand ...

component, but the ''Y'' tristimulus value of the XYZ color space or a lightness index similar to ''W''* of the CIE 1964 color space are sometimes used. Today, the CIE 1960 UCS is mostly used to calculate

correlated color temperature Color temperature is the color of light emitted by an idealized opaque, non-reflective body at a particular temperature measured in kelvins. The color temperature scale is used to categorize the color of light emitted by other light sources ...

, where the isothermal lines are perpendicular to the Planckian locus. As a uniform chromaticity space, it has been superseded by the CIE 1976 UCS.

Background

Judd determined that a more uniform

color space A color space is a specific organization of colors. In combination with color profiling supported by various physical devices, it supports reproducible representations of colorwhether such representation entails an analog or a digital representa ...

could be found by a simple

projective transformation In projective geometry, a homography is an isomorphism of projective spaces, induced by an isomorphism of the vector spaces from which the projective spaces derive. It is a bijection that maps lines to lines, and thus a collineation. In genera ...

of the

CIEXYZ The CIE 1931 color spaces are the first defined quantitative links between distributions of wavelengths in the electromagnetic visible spectrum, and physiologically perceived colors in human color vision. The mathematical relationships that defin ...

tristimulus values: :

\begin ''R'' \\ ''G'' \\ ''B'' \end = \begin 3.1956 & 2.4478 & -0.1434 \\ -2.5455 & 7.0492 & 0.9963 \\ 0.0000 & 0.0000 & 1.0000 \end \begin X \\ Y \\ Z \end

(Note: What we have called "G" and "B" here are not the G and B of the

CIE 1931 color space The CIE 1931 color spaces are the first defined quantitative links between distributions of wavelengths in the electromagnetic visible spectrum, and physiologically perceived colors in human color vision. The mathematical relationships that def ...

and in fact are "colors" that do not exist at all.) Judd was the first to employ this type of transformation, and many others were to follow. Converting this RGB space to chromaticities one finds Judd's-UCS

u_=\frac = \frac

v_=\frac = \frac

MacAdam simplified Judd's UCS for computational purposes: :

u = \frac

v = \frac

The Colorimetry committee of the CIE considered MacAdam's proposal at its 14th Session in Brussels for use in situations where more perceptual uniformity was desired than the (x,y) chromaticity space, and officially adopted it as the standard UCS the next year.

Relation to CIE XYZ

U, V, and W can be found from X, Y, and Z using: :

U= \textstyleX

V=Y\,

W=\textstyle(-X+3Y+Z)

Going the other way: :

X=\textstyleU

Y=V

Z=\textstyleU-3V+2W

We then find the

variables as: :

u =\frac U= \frac

v =\frac V= \frac

We can also convert from ''u'' and ''v'' to ''x'' and ''y'': :

x = \frac

y = \frac

Relation to CIE 1976 UCS

u^\prime = u\,

v^\prime = \textstylev\,

References

External links

Free Windows utility to generate chromaticity diagrams.
Delphi source included. {{color space Color space