Warp schrieb:
>   It is a problem when POV-Ray ignores the File_Gamma setting, as seems to
> be currently the case.

No, it doesn't. It just affects file output in a way different from what 
you seem to expect.

>   Anyways, I don't really understand the reason to have a different gamma
> setting for displaying the preview image on screen and another for writing
> the image data to a file. If you specify different values, you will not get
> what you see, but something different.

Then don't do that.

But what if for instance your display has a gamma of 1.8, but you want 
to generate pictures to be displayed on the web with a targetted display 
gamma of 2.2?

>>>   Btw, a Display_Gamma of 1.0 produces (on screen) an image which is
>>> basically identical to what POV-Ray 3.6 produces, all image_maps look
>>> correct, etc. Is there a reason why it cannot be the default?
> 
>> Yes, there is: It's perfectly wrong for most systems.
> 
>   Then every single program out there which displays image is wrong, and
> POV-Ray is the only program which is right?

That's not what I said.

It's not an /output/ problem - it's an /input/ problem.

>   However, when I tell POV-Ray to use a Display_Gamma of 1.0, then it will
> start showing the image in the exact same way as all the other programs.

Even though this approach may /appear/ to be right at first glance, it 
is /not/, because you're then trying to apply POV-Ray's computations 
(which are designed to be done in linear color space) in the 
gamma-precorrected domain,

>   If a Display_Gamma (and, I assume, File_Gamma when it's fixed) of 1.0
> is not the proper way of fixing this problem, then please tell me what is.
> Because as it is now, the default setting makes image_maps completely
> unusable.

There are two answers to this:

(A) The correct /solution/ is to fix POV-Ray's input file gamma 
handling, which must currently be considered problematic at best.

(B) The correct /workaround/ until then is to convert your input files 
to a file format handled properly by POV-Ray; I got good results with 
using IC to convert JPEG files to PNG files (I'm told that IC adds a 
gAMA chunk, which POV-Ray can use to properly convert it to linear color 
space), and before that I used HDRShop to convert to HDR format.

And to repeat myself: No, File_Gamma is not broken and therefore needs 
no fixing. Output file gamma handling is right to all of my knowledge. 
(I'll stand corrected if you can provide a scene and settings 
unambiguously showing POV-Ray to mess up file output.)

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