clipka <ano### [at] anonymousorg> wrote:
> Am 01.03.2012 04:13, schrieb JamesB7271:
> > Hello,
> >
> > I am new to POV-Ray and have just upgraded from POV-Ray 6 to POV-Ray 7. I notice
> > now that all my renders seem too bright. As an extreme example: if I render a
> > simple sphere over a flat plane in a scene that has no light sources, I can
> > clearly see both the sphere and the plane (although somewhat dimmed). With
> > version 6 I believe a scene with no light sources would render completely black,
> > which I think is correct for a scene with no lights.<-(is this a correct
> > assumption?)
> >
> > I read that there were some changes made to Gamma settings in version 7? How do
> > I get it back to normal?
>
> (Just for the records: I tend to become somewhat itchy when people refer
> to the 3.6 or even 3.5 gamma handling as "normal", because it isn't -
> it's obsolete, with POV-Ray 3.7's default gamma handling being far
> superior.)
>
> There are multiple ways of achieving what you're asking for, the
> simplest being to tell POV-Ray that your scene was designed for POV-Ray
> 3.6; just insert the following line at the beginning of your scene file:
>
>      #version 3.6;
>
> POV-Ray 3.7 will then (among other things) automatically switch to a
> gamma handling mode that is backward compatible with POV-Ray 3.6 (with
> minor exceptions relating to PNG input images).
>
> In addition, if you explicitly specify "Display_Gamma" somwehere in your
> .ini files, you also need to set "File_Gamma" to the same value (unless
> you're using PNG, OpenEXR or Radiance HDR as output format).
>
> If you do not specify "Display_Gamma", you may still see slight
> differences in dark image regions; if you consider that a problem,
> explicitly specify "Display_Gamma=2.2" and "File_Gamma=2.2" to iron
> those out.
>
>
> Alternatively, specifying "assumed_gamma srgb" will give you essentially
> the same gamma-related behaviour as POV-Ray 3.5 (or POV-Ray 3.6 without
> any "assumed_gamma" statement), except for gamma handling of any input
> images.
>
> If your scenes already contain an "assumed_gamma" statement, gamma
> handling in 3.7 /should/ automatically be essentially the same (again
> except for input images), and your observed changes should be a no-issue.
>
> In both cases, the aforementioned advice for "Display_Gamma" and
> "File_Gamma" also applies.
>
>
> I hope this helps. For future scenes, if realism is of any concern to
> you I strongly recommend using "#version 3.7" and "assumed_gamma 1.0",
> leaving "File_Gamma" at its default, and using the new "srgb" family of
> color keywords instead of "rgb" to specify colors taken from external
> applications.

Thank you so much for the detailed response. I of course want the most realism,
so I do want to make sure I'm getting started right.
Below is a simple sample scene (partly from the tutorials). If I render it as
shown below, it looks too bright and washed out to me. However, if I change the
"#version" statement to 3.6, or change the "assumed_gamma" statement from 1.0 to
srgb, the scene seems to look more realistic. Can you try it and give me your
opinion? If the new 3.7 gamma handling is the correct and more accurate method,
then I think I may be doing something else wrong?

---------------------------------------------
#version 3.7

global_settings {
 assumed_gamma 1.0
}

#include "colors.inc"
#include "stones.inc"

camera {
  location <0, 3, -4>
  look_at <0, 1, 2>
}

sphere {
  <0, 1, 2>, 2
  texture {
    pigment {color Yellow}
  }
}

plane { <0, 1, 0>, -1
  texture {T_Stone25
  }
}

light_source {
 <2, 10, -3>
 color White
 area_light <5, 0, 0>, <0, 0, 5>, 5, 5
   adaptive 1
   jitter
}
---------------------------------------------

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