Am 16.03.2017 um 15:06 schrieb Bald Eagle:
> clipka <ano### [at] anonymousorg> wrote:
> 
>> To be honest, no, I don't remember those lamentations.
>> Sounds pretty much like a gamma issue to me.
> 
> It was Oct 2014, so not surprising.
> 
> http://news.povray.org/web.5435881bcbb3d8155e7df57c0%40news.povray.org

`[0.4 rgb <184/255, 115/255, 48/255> * Tone]`

Yeah. Any expression starting with "rgb" and containing integer numbers
divided by 255 screams "gamma issue!" at the top of its lungs.

Integer numbers divided by 255 are a sign that the colour were
originally encoded as a byte triplet, most likely raw image values, e.g.
as picked from an image using external tool.

Raw image values typically use non-linear colour values, the best bet
being sRGB.

To specify sRGB colours, you need to use the `srgb` keyword instead of
`rgb`, otherwise you get the colour's gamma wrong.

Unless your scene uses `assumed_gamma srgb` (or an approximate value,
such as `assumed_gamma 2.2`), in which case your entire image suffers
from gamma issues.


(It should be noted that `srgb <184/255, 115/255, 48/255> * Tone`
doesn't give you exactly what you are asking for. Theoretically it
should be `(srgb <184/255, 115/255, 48/255>) * Tone`, but that's
currently not allowed by the parser.)

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