"Tony[B]" wrote:
> 
> I don't normally use it. It takes a post from Kari to get me thinking about
> it.

All povray lighting calculations are done using normal linear intensites.
Monitor output intensity follows roughly function out = in^gamma. If
a pixel in a scene should be at 50% intensity the actual value that
is fed to the monitor should be 50%^(1/gamma) = 70% if the monitor gamma = 2.
In other words an image using linear intensities must be gamma corrected
so that the monitor displays the image correctly. Display_Gamma in master
povray.ini is the gamma. global_settings{assumed_gamma 1.0} instructs
pov to apply the correction to the image file.

I don't know how this can be explained more clearly. Maybe like this:
Povray thinks that when it sets a pixel at 20% intensity you will also
see it at 20% intensity. Povray is wrong! You will see the pixel at
20%^gamma = 4% intensity. Clearly not good. Use gamma correction and you will
see what povray wanted you to see.


RTFM & Gamma FAQ folks. 

_______________________________________________________________________
Kari Kivisalo                                   http://www.kivisalo.net

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