Re: Color saturation and contrast (was Re: New Fuji Film: Astia)

[P3D John Ohrt <johrt@xxxxxxx>]

Gary Nored wrote:
> I agree that increasing saturation must increase contrast somehow --
> I've noticed the same thing when manipulating images on my computer
> screen. I haven't got a clue why ... the answer is probably full of
> gamma formulas, derivations, and other stuff full of (horrors!)
> _numbers!_

I don't think increasing saturation increases contrast.  If you convert
RGB to IHS (Intensity,Hue,Saturation) and start playing with contrast,
brightness and gamma, I believe that you will find only intensity is
altered.  Hue uniquely specifies the "color" and saturation specifies
the "purity of the color".  

eg.

If the intensity is 50%, the hue is red, then with no saturation the
pixel will appear  red.  With 100% saturation, the pixel will appear
white regardless of the hue, and somewhere in between, the pixel will
appear pink.  If the intensity is 0%, the pixel will appear black
regardless of the hue and saturation, and if the intensity is 100% the
color will be the most intense red available.

IHS was originally invented to ease the communications between display
designers (engineers) and the optics scientists.  It is conceptually
quite simple, but doesn't recognize the nonlinear nature of viewing, so
you have to be carefull how you use it.  

Regards
--
John Ohrt,  Regina, SK, Canada
johrt@xxxxxxx


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