The three-dimensional colour space produced by plotting CIE tristimulus values
(X,Y,Z) in rectangular coordinates is not visually uniform, nor is the (x,y,Y) space nor
the two-dimensional CIE (x,y) chromaticity diagram. Equal distances in these spaces
do not represent equally perceptible differences between colour stimuli. For this
reason, in 1976, the CIE introduced and recommended two new spaces (known as
CIELAB and CIELUV) whose coordinates are non-linear functions of X, Y and Z. The
recommendation was put forward in an attempt to unify the then very diverse practice
in uniform colour spaces and associated colour difference formulae. Both these
more-nearly uniform colour spaces have become well accepted and widely used.
Numerical values representing approximately the magnitude of colour differences
can be described by simple Euclidean distances in the spaces or by more
sophisticated formulae that improve the correlation with the perceived size of
differences.
The purpose of this CIE Standard is to define procedures for calculating the
coordinates of the CIE 1976 L*a*b* (CIELAB) colour space and the Euclidean colour
difference values based on these coordinates. The standard does not cover more
sophisticated colour difference formulae based on CIELAB, such as the CMC
formula, the CIE94 formula, the DIN99 formula, and the CIEDE2000 formula nor
does it cover the alternative uniform colour space, CIELUV.
| Number of Pages : | 12 |
| Published : | 09/01/2007 |
