Am 02.06.2011 21:38, schrieb Alain:

> file_gamma affect how the image is actualy writen to a file.
> display_gamma adjust the preview display.
>
> For a PNG, it sets the gamma chunk of the file. For other formats that
> don't have such a mechanism, it adjust the pixels values according to
> the set value.

Not exactly; for a PNG, POV-Ray "adjusts" (or, more precisely, encodes) 
the pixel values according to the set value as well; however, the 
corresponding gamma value is indeed written to the gamma chunk of the 
file, so that the viewing application can determine the encoding gamma, 
and from that compute the original data. Therefore, the File_Gamma 
setting typically does not affect how a PNG file appears in an image 
viewer (except for some influence on banding or dithering artifacts).

> Idealy, file_gamma should be set at the same value as display_gamma and
> assumed_gamma.

Um... no.

File_Gamma should /typically/ be set to the same value as Display_Gamma.

assumed_gamma should ideally be set to either 1.0 (for realistic 
renders), or to the same value as Display_Gamma (for certain artistic or 
ease-of-use benefits at the cost of some degree of realism).

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