The CIE1976 L*a*b* space is a color opponent space that aims to
be perceptually uniform, so that one unit in the space corresponds
to a just noticeable difference in color. The L* dimension
corresponds to visual lightness, while the a* corresponds
approximately to redness/greenness, while b* corresponds
approximately to yellowness/blueness. It is the direct basis of
the CIE
Delta E 76, and the base for latter, more refined color
difference metrics such as CIE Delta
E 94 and CIE Delta
E 2000, as well as basis of the DIN99
Delta E color space. While it is approximately perceptually
uniform, it is not perfect, showing some hue linearity problems in
the blue region, and exaggerating color distances somewhat for
more saturated colors.
It is a white relative space, where the reference white has the
L*a*b* value 100,0,0. The typical assumption is that an observer
is adapted to the white reference, so that the L*a*b* coordinates
correspond to the colors relative to that white.
Details of white point
configuration.