When using POV-Ray 3.61 the following all produce the same image(as far as I can
tell).
For any file with assumed_gamma 2.2 in the global settings.

#if (version < 3.7)
  #version 3.5;
  global_settings { assumed_gamma 2.2 }
#end

and, in the command line.
-w768 -h576 +a0.3 Output_File_Type=t
or
-w768 -h576 +a0.3 Output_File_Type=s
or
-w768 -h576 +a0.3 Output_File_Type=n

With POV-Ray 3.7b the gamma correction has changed to the command line only.
To get the same picture as in 3.61, I need to use:
-w768 -h576 +a0.3 Display_Gamma=1 File_Gamma=1 Output_File_Type=xx

Without 'File_Gamma=1' the picture looks the same in Winpov render window, but
the resulting image looks different(than 3.61) in an image editor.

Is this the correct way to update scene files for 3.7b?

Stephen S

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"StephenS" <nomail@nomail> wrote in message 
news:web.48b8a3842751955c30d5e6ea0@news.povray.org...
> When using POV-Ray 3.61 the following all produce the same image(as far as 
> I can
> tell).
> For any file with assumed_gamma 2.2 in the global settings.
>
> #if (version < 3.7)
>  #version 3.5;
>  global_settings { assumed_gamma 2.2 }
> #end
>
> and, in the command line.
> -w768 -h576 +a0.3 Output_File_Type=t
> or
> -w768 -h576 +a0.3 Output_File_Type=s
> or
> -w768 -h576 +a0.3 Output_File_Type=n
>
> With POV-Ray 3.7b the gamma correction has changed to the command line 
> only.
> To get the same picture as in 3.61, I need to use:
> -w768 -h576 +a0.3 Display_Gamma=1 File_Gamma=1 Output_File_Type=xx
>
> Without 'File_Gamma=1' the picture looks the same in Winpov render window, 
> but
> the resulting image looks different(than 3.61) in an image editor.
>
> Is this the correct way to update scene files for 3.7b?

Stephen:

Is this perhaps what you are seeing? I asked (what I think) was a simular 
question and Chris answered with this:

>>Jim Holsenback wrote:
>> advanced/grenadine as a test case I noticed a difference in the preview
>> window image (to dark) and the final png image file (to light).

> Chris Cason wrote:
> Please be aware that the PNG output images have the inverse gamma
> written into the file header and will appear differently between
> viewers that do and don't support using this value.

Jim

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"Jim Holsenback" <jho### [at] hotmailcom> wrote:
> ...
> Is this perhaps what you are seeing? I asked (what I think) was a simular
> question and Chris answered with this:
>
> >>Jim Holsenback wrote:
> >> advanced/grenadine as a test case I noticed a difference in the preview
> >> window image (to dark) and the final png image file (to light).
>
> > Chris Cason wrote:
> > Please be aware that the PNG output images have the inverse gamma
> > written into the file header and will appear differently between
> > viewers that do and don't support using this value.
>
> Jim

Yes, but a Windows bmp file format also shows this.

Stephen S

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"StephenS" <nomail@nomail> wrote in message 
news:web.48b91ee5ddcc1fa02473e82c0@news.povray.org...
> "Jim Holsenback" <jho### [at] hotmailcom> wrote:
>> ...
>> Is this perhaps what you are seeing? I asked (what I think) was a simular
>> question and Chris answered with this:
>>
>> >>Jim Holsenback wrote:
>> >> advanced/grenadine as a test case I noticed a difference in the 
>> >> preview
>> >> window image (to dark) and the final png image file (to light).
>>
>> > Chris Cason wrote:
>> > Please be aware that the PNG output images have the inverse gamma
>> > written into the file header and will appear differently between
>> > viewers that do and don't support using this value.
>>
>> Jim
>
> Yes, but a Windows bmp file format also shows this.
>
> Stephen S

I think your Display_Gamma setting needs to be tweaked. I noticed that the 
preview image and the final (png) image looked different so I changed 
Display_Gamma until both images appeared the same. If I'm understanding 
correctly this is similar to the process outlined in the help feature 
(black/gray bars). What looks good for me may or may not look good for you 
(unless we happen to have exactly the same display hardware). I've been 
using Display_Gamma=2.5 on my v3.6.1 setup forever and this also worked for 
the v3.7 scene files. I compared several randomly picked (NOT ALL) of the 
v3.7 files with what they looked like rendered with v3.6.1 and didn't see 
any difference. I then started queuing up the files and went for it. When I 
was done I did a quick QA of ALL the v3.7 scene files using a slideshow type 
viewer. I felt OK with the results so I thought a cursory inspection was 
adequate.

Cheers Jim

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