Will W wrote:
...
>>The way I understand it is you set assumed_gamma to 1 and leave it
>>alone, as others have said, it may be less confusing if it were a
>>boolean option to select whether gamma correction is applied to the
>>output. You develop your scene using display_gamma set to 1.8, and do
>>any renders designed to be viewed on similar systems the same way. When
>>you do a render designed to be viewed on systems with display systems
>>having a gamma value nearer 2.2, you change the display_gamma value to
>>2.2 for the final render. It looks bright on your monitor, but you send
>>it off to a PC user and it looks spot on when they view it on their
>>gamma 2.2 system.
> 
> 
> That sounds like an alternate approach that could work. However it isn't the
>  one that's implemented in POV-Ray.

I maintain that it is.

Take this concrete example: You have a setup that delivers a display 
gamma of 1.8, so you set display_gamma = 1.8 in POV. You create a new 
scene with assumed_gamma = 1 and you render yourself some nice 
wallpaper. You send this wallpaper to a friend with a system that 
delivers a display gamma of 2.2, and she complains that it is too dark. 
You remedy this situation by re-rendering it with assumed_gamma changed 
from 1 to 2.2. Only trouble is, going from an assumed_gamma of 1 to an 
assumed_gamma of 2.2 makes the image *darker*. Try it and see.

Now my method: Same up to where the friend complains, then you remedy 
the situation leaving assumed_gamma alone and changing display_gamma 
from 1.8 to 2.2. This creates a brighter image and your friend can see 
the wallpaper just fine.

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