Am 26.06.2010 13:24, schrieb Gyscos:
> clipka<ano### [at] anonymousorg>  wrote:
> [...]
>> Let me guess - you used PNG file output? In that case it is a sign that
>> /Firefox/ is getting it right, while gimp and the image viewer are not.
>> The File_Gamma setting does not affect PNG output very much (provided
>> that your image processing software is handling gamma right), except for
>> banding artifacts.
>
> But the POV-Ray preview was identical to what I get in Gimp or window viewer...
> Is that normal ?

If you set Display_Gamma=1.0, then yes - you'll typically get a wrong 
preview...

> Display_gamma and File_Gamma being identical doesn't mean the preview and the
> output image - when correctly decoded - are the same ?

That depends.

Display_Gamma always specifies the gamma pre-correction to apply in 
order to show a correct preview.

File_Gamma strictly speaking doesn't specify gamma pre-correction, but 
gamma encoding (or, even more strictly speaking, the inverse of the 
encoding gamma). For some older file formats, like BMP or JPEG, where 
gamma encoding double-features as gamma pre-correction, this happens to 
be the same; PNG, on the other hand, includes information about the 
encoding gamma used in the file header, so that it can be left all up to 
the viewing software to perform both gamma decoding and gamma 
pre-correction for display. And for HDR and OpenEXR file formats, 
File_Gamma has no effect whatsoever because those file formats always 
use linear encoding.

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