On Fri,  7 Feb 2003 05:37:42 EST, "Exether"
<exe### [at] demoxandmailcom> wrote:

>Where img_col.png is a uniform image of the <112,57,57> color (#703939) made
>with GIMP. What I see is that the mapped sphere is darker when I expected
>it to be the same. Then I try to get the same color by changing the first
>sphere's color to 0.5*<112,57,57>/255 so that they are about the same
>brightness. But then the mapped sphere seems to be more Red that the other
>one.
>

It's gamma correction.  The PNG file format has gamma information
in it.  This is theoretically a good idea but in practice it seems
that many programs either have proken file gamma support or they
each interpret gamma differently.

I use a 2-step method of working around this:

(1) use a file format with no gamma (such as TGA or BMP).
(2) set the assumed_gamma in the global_settings part
    of your POV file to be the same as the display_gamma
    setting in the povray.ini file

This disagrees with what is considered proper in theory and
in the documentation, but it works.  I don't argue with
what works.

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