clipka <ano### [at] anonymousorg> wrote:
> Am 27.12.2016 um 09:21 schrieb Kenneth:
>
> > I decided to run your test scene with assumed_gamma 1.0 instead of 2.2, and
> > noticed something about your use of 'rgb' in the light_source. I changed it to
> > srgb (which I've started doing in all my v3.7xx scenes, to be 'color-consistent'
>
> BTW, there's a caveat when using "srgb" in light sources: To modify the
> brightness without affecting the hue, you need to use
>
>     colour (srgb <R,G,B>)*Brightness
>
> rather than
>
>     colour srgb <R,G,B>*Brightness
>
> because the latter would be interpreted as
>
>     colour srgb (<R,G,B>*Brightness)
>
> and in the sRGB world multiplying a colour vector by a constant does
> /not/ correspond to an even scaling of the corresponding linear colour
> components. (That would work for f(x)=pow(x,2.2), but sRGB gamma is more
> complicated than that.)

The moral seems to be get all of your srgb declarations out of the way as early
as possible--including before you do any math on such colors.

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