clipka <ano### [at] anonymousorg> wrote:
> Your .png file has a gAMA chunk indicating that you set File_Gamma=1.0,
> or are using #version 3.6 and assumed_gamma 2.2 (I'm presuming here that
> you're using POV-Ray 3.7); while this is not wrong /per se/, it has some
> drawbacks:
>
> - You're not taking advantage of /gamma encoding/; as a consequence, at
> a depth of 8 bits per color channel you're risking noticeable color
> banding in dark areas.
>
> - The images are not inherently /gamma pre-corrected/ for a typical
> computer; as a consequence, software that doesn't evaluate the gAMA
> chunk will present the midtones /darker/ than they should be (except on
> systems calibrated for a non-typical gamma, such as linear gamma).
>
> With POV-Ray 3.7, it is strongly recommended to work without
> assumed_gamma, and set File_Gamma=2.2, for any image (or scene, for that
> matter) you plan to share with others.
>
> That said, it seems to me that Firefox is doing it right (at least on
> systems with a display subsystem gamma of around 2.2): In the case of
> this particular file, it is the more washed-out version that is right.

Hi,

I'm using version 3.7 on Windows XP. The darker image is closer to what I
intended (although it's a little too dark due to ineptness on my part). To
correct the gamma issues, I followed the instructions on the Beta page and added
the lines

     display_gamma=1.0
     file_gamma=1.0

to the povray.ini file, and removed "assumed_gamma 2.2" from the scene file.
That seemed to produce the desired result in the render window and the output
file. I know this isn't right either, since you're recommending setting
file_gamma to 2.2. However, when I set file_gamma to 2.2 the image appears
washed-out and I can't seem to fix that by adjusting the scene lighting. Maybe
my video card is set wrong or something.

On my computer:

     Version 3.7
          no assumed_gamma
          display_gamma=1.0
          file_gamma=1.0

seems to produce the same result as

     Version 3.6:
          assumed_gamma 2.2

If I'm not understanding something or doing something wrong I apologize.

Regards,
Dave Blandston

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