Re: Color saturation and contrast

[P3D John Ohrt <johrt@xxxxxxx>]

P3D Joerg Meyer Inf.] wrote:


> I think you're mixing up two models here: HSV (hue, saturation, value)
> and HLS (hue, lightness, saturation).

There are similar models going by different names, but the IHS could be
a misnomer, I just can't remember and the books are packed for moving.

The models and the terminology simply aren't standardized.


> Increasing saturation not necessarily increases contrast, since contrast
> is a term which is not included in one of these color theories. Contrast
> refers to a difference between two colors, and it depends on the measure
> (RGB distance, luminosity, etc.) which describes it. For example, if
> you have two colors with L = 0.3 and L = 0.4 respectively (difference:
> C = 0.1), and you double the lightness (L = 0.6 and L =0.8 resp.),
> the contrast also doubles (C = 0.2).

Well that is one definition, but as I alluded in the previous message,
HSV, HSL, RGB, CYM, CYMK all suffer from the same problem, they don't
take into account many of the nonlinear aspects of viewing.  I think
this is why the pros don't waste much time on trying to standardize
terminology on these simple models.  For openers, they can't provides
pure (unstaurated) colors except at the primaries.  This makes
conversion between models sometimes tricky ... rgb to cym being an
example.  Having said that, that doesn't make the models worthless or an
unuseable basis for "good enough" image processing for some
applications.

But this is getting off topic.  The best general reference I know of is:

http://www.inforamp.net/~poynton/Poynton-articles.html

The one on colour, is called color.pdf, highly reccomended over the text
and html versions.

Thanks for your input.

> 
> To find out what happens if you increase saturation, you could convert
> an HSV or HLS color to the RGB model and calculate the RGB distance.
> 
> Joerg
> 
>     _V_     | Joerg Meyer ----- University of Kaiserslautern, Germany
>    /   \    | Department of Computer Science, Computer Graphics Group
>    |O O|    | mailto:jmeyer@xxxxxxxxxxxxxx --------------------------
> ooO--U--Ooo | http://davinci.informatik.uni-kl.de/~jmeyer -----------

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


------------------------------