Am 29.06.2010 11:44, schrieb Gyscos:
> But then, in theory, this gamma value just affects the transition, it shouldn't
> change the final image (except for this precision improvements), right ?
> So whatever File_Gamma I set, the correctly decoded image should have pretty
> much the same brightness ?

Yes - at least for PNG files: Provided you use a file viewer that does 
its homework properly, PNG files created by POV-Ray 3.7 look (almost) 
identical regardless of how you set File_Gamma.

For the other files like JPEG or BMP it's not that easy because the file 
viewer doesn't know the encoding gamma used (that information is not in 
the file header), and will have to resort to wild guessing. Typically, 
it will expect a value of around 1/2.2, corresponding to File_Gamma=2.2, 
so any significantly different value will make the file viewer display 
the image differently.


As a general rule, you should keep File_Gamma set to 2.2 (the default), 
because that's what most file viewers will expect for JPEG, BPM and the 
like - and it doesn't hurt for PNG either, giving a very efficient encoding.

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