Zeger Knaepen wrote:
> I've never really understood why POV-Ray should do gamma-correction.  Isn't that up
to the display-drivers?  Wouldn't it be more logical if POV-Ray just assumed that 50%
of the RGB-values give 50% of the brightness ?

That might be good but in reality it isn't.  In fact these days it would 
probably make sense to have all display devices perform gamma correction 
internally.  Instead there is the sRGB standard which uses a gamma of 
2.2.  Some (usually more expensive) monitors have an sRGB setting where 
they act as an sRGB device and transform the signals to their own 
characteristics internally.

Note current implementations of the X-Window system support adjusting 
gamma correction for the graphics display globally (might be subject to 
support by the display driver):

http://wiki.x.org/X11R6.8.0/doc/xorg.conf.5.html#sect9

but it hardly makes sense to use this to get a linear characteristic of 
the display since all colors (on websites, in images or elsewhere) will 
be displayed incorrectly (unless *all* the programs you use can render 
into linear color space).  What makes sense is to use this feature to 
adjust for the difference between your monitor and sRGB (either by 
estimation or using an actual calibration device).

> Now, as I understand it, that *is* the default behaviour of POV-Ray, but then why do
some image_maps look a lot darker than they should?  What are the correct settings to
completely turn off any gamma-correction ?

If you don't specify any assumed_gamma in the scene file the render is 
done without any gamma correction.

Christoph

-- 
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http://www.imagico.de/ (Last updated 31 Oct. 2005)
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