Lightness and Brightness and Other Confusions

Yellow +b*
60
50
40
Hue
30
20
10
-60 -50 -40 -30 -20 -10
Green -a*
10
20
30
40
50
60
Red +a*
-10
-20
-30
-40
-50
-60
Blue -b*
100
90
80
70
60
50
h
Lightness (L*)
40
30
Hue
20
10
0
10 20 30 40 50 60
Chroma (C*)
Figure 20. The L*C*h* colour space is a cylindrical variation of the spherical
CIELAB space. The hue angle (indicating hue) rotates counter-clockwise
from +a (red = 0˚). The chroma increases outwards from the central axis
(grey scale = 0 chroma).
Chromaticness and chromaticity
Chromaticness is often given the same definition as chromaticity, i.e. the hue
and saturation of a colour regarded independent of its brightness. The Collins
English Dictionary still gives chromaticness as “the attribute of colour that
involves both hue and saturation” (Collins 2000). Billmayer and Saltzman
give chromaticness as follows: “Finally, when taken together, the hue and
saturation of a perceived colour are called its chromaticness”. In their book
The Science of Color The optical Society of America’s Committee on Colorimetry
defined chromaticness as follows: “Chromaticness consists of hue and
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