Experiment No: 03
Experiment Name: Define Hue, value and chroma,
explain uniform (L* a* b*) 3 dimensional color space according to CIE Lab
system.
Fig: Uniform (L* a* b*) 3 dimensional color space.
Figure:
CIE Lab system:
CIE stands for commission of internation’ale E’clarge.
In 1976 CIE recommended the CIE L* a* b* (Three dimensional
color system) system. The system is intended to be a uniform color space with
the following properties:
(1) A rectangular three dimensional color space (L* a* b*) in
which all surface color can be represented.
(2) The distance between the points representing the colors
of two sample is proportional to the visual color difference between them.
(3) L* a* b* values can be easily interpreted in terms of
hue, lightness (value) and depth of color (chroma).
(4) L* is the vertical axis and represents lightness 0 being
a perfect black and 100 a perfect white.
(5) a* in the axis in the plane normal to L* which represent
redness (a*+) and greenness (a*-).
(6) b* in the axis normal to both L* and a* which indicate
yellowness and balances
h0 = 00 Perfect red.
h0 = 3600 Perfect red.
h0 = 450 Orange.
h0 = 1350 Lime green (light green).
h0 = 2250 Cyan.
h0 = 2700 Blue.
h0 = 3150 Magenta.
Figure:
In CIE L* a* b* space the color difference between a standard
and a trial sample is expressed by numerically DE.
\ DE = √(("" L^(*2)+ "" a^(*2)+ "" b^(*2)))
Where
= LT
– LS (S = Std, T = Trial)
