Select a colour using any of the coordinate systems, the CIE 1931
chromaticity model, the CIE 1960 UCS, the CIE 1976 UCS, or with
Tcp and Δuv. Lock/Unlock the reticle on
the CIE models by clicking on the graph. Observe how the
coordinates interact with each other as they describe a colour.
It is important to remember that colours used in the backgrounds
of the CIE models are representativ only. The device being used
to display this page is capable of reproducing only a subset of
the visible chromaticity gamut.
The MacAdam Ellipse drawn on the CIE 1931 graph is flawed. It is
calculated as quadratic curves from the quadrants of a circle on
the CIE 1976 graph. In CIE 1976, a circle is only an approximation
of the MacAdam Ellipse. It is drawn with an arbitrary radius of 0.01
An objective specification of the quality of a color regardless
of its luminance.
The International Commission on Illumination (usually
abbreviated CIE for its French name, Commission
internationale de l'éclairage) is the international
authority on light, illumination, colour, and colour spaces.
It was established in 1913 as a successor to the
Commission Internationale de Photométrie and is today
based in Vienna, Austria.
CIE 1931 (x,y)
The first defined quantitative links between distributions of
wavelengths in the electromagnetic visible spectrum, and
physiologically perceived colors in human color vision.
CIE 1960 UCS (u,v)
The CIE 1960 UCS is mostly used to calculate
correlated color temperature, where the
isothermal lines are perpendicular to the Planckian locus. As a
uniform chromaticity space, it has been superseded by the CIE
CIE 1976 Luv (u',v')
A CIE colour space which attempted perceptual uniformity.
Additive mixtures of different colored lights will fall on a
line in this model's uniform chromaticity diagram (dubbed the
CIE 1976 UCS). Unless the mixture is of constant lightness,
this is true only for the chromaticity diagram and not the
CIELUV colour space.
v′ is 1.5 times as large as v its 1960 predecessor.
Chromaticity difference can be calculated as the Euclidean
distance of the u'v' coordinates of two colours.
How close (length of the hypotenuse) the Tcp of a u,v
coordinate is to the Planckian locus. The CIE only considers
values to be meaningful within Δuv =
Positive values are +green, negative values are +magenta.
Specifies a standardized color space and defines the locations
of the RGB primaries and the White Point for the purpose of
facilitating the communications between lighting controllers and
color‐changing luminaires. The method is generic and is neither
manufacturer‐specific nor color technology‐specific.
The Arri Skypanel conforms to this communications standard,
begining with firmware 3.0, for both calibrated RGB and x,y
The path that the color of an incandescent black body would take
in a particular chromaticity space as the blackbody temperature
A method to estimate the correlated color temperature by way of
interpolation from look-up tables and charts. Robertson's method
takes advantage of the relatively even spacing of the mired
scale to calculate Tcp using linear interpolation of
the isotherm's mired values.
The correlated Planckian temperature (CCT,
Tcp) is the temperature of the Planckian radiator
whose perceived color most closely resembles that of a given
stimulus at the same brightness and under specified viewing
-- CIE/IEC 17.4:1987, International Lighting Vocabulary (ISBN
Although the CCT can be calculated for any chromaticity
coordinate, the result is meaningful only if the light sources
are nearly white. Beyond a certain value of Δuv,
a chromaticity co-ordinate may be equidistant to two points on
the locus, causing ambiguity in the CCT.
A chromaticity diagram which attemps to have uniform spacial
distance between coordinates of equal color distance.