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The RGB system is understandable because it is cartesian, and we all
learned cartesian coordinates in school. But it doesn't help us
create a tint or shade of a color; we cannot say, ``We want orange,
and a lighter shade of orange, or a less vivid orange''. With HSV we
can do this, by saying, ``Orange must be between red and yellow, so
its hue is about
= 30°; a less vivid orange has a lesser
, a darker orange has a lesser
''. On the other hand,
the HSV system is a peculiar geometric construction, more like a cone (Figure I.3). It is not an
orthogonal coordinate system, and it is not found by a matrix
transformation of RGB; these make it difficult in some cases too.
Note that a move toward black or a move toward white will change both
and
, in the general case of an interior point in the
cube. The HSV system also doesn't behave well for very dark colors,
where the gray point is near black and the two lines we constructed
above are almost parallel. If you are trying to create nice colors
for drawing chocolates, for example, you may be better off guessing
in RGB coordinates.
Next: I.7 CMYK color system
Up: I. Color Space: The
Previous: I.5 Artificial illumination
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Paul Wessel
2009-02-16