Am 29.08.2012 02:20, schrieb Christian Froeschlin:
> looks great even in srgb ;) (and my monitor would be too old anyway)
>
thanks ;)

> Do I understand correctly that you define colors in adobe rgb,
> manually convert them to "linear adobe rgb" (x^1/2.2), render in
> povray using file_gamma 2.2, reinterpret the output using an
> adobe rgb profile and then convert to srgb?
>
Exactly! Better explained than I could - as usual. A minor detail is 
that I did use OpenEXR output as always and did assign a linear 
Adobe-RGB profile to it. Converting to sRGB was the last step when 
writing the JPEG file.


> And that this gives significantly different results compared to
> using "linear srgb" (for lack of better term) via "srgb x" (not
> x^1/2.2) and rendering using file_gamma srgb?
>
Yes, in this case where under the strong "neon" lighting highly 
saturated colors do result. And just to make it clear "srgb x" does not 
mean the "srgb" POV-Ray keyword it just means rgb values that do assume 
sRGB primaries and are manually converted from the original Adobe-RGB 
values using a color space transformation - and as just linear gamma is 
involved this boils down to a simple matrix multiplication.

> Interesting ... but it may not be so surprising after all if your
> input colors are at extreme limits. Consider a pigment of maximum
> adobe rgb red <255/255, 0.0, 0.0>. If lighting causes the output pixel
> to be <240/255, 0.0, 0.0>, it is still outside srgb gamut and may end
> up with maximum saturation after conversion, whereas clipping the
> input value to srgb yields an srgb output of <240/255, 0.0, 0.0>.
>
> As a sanity check, have you tried rendering in adobe rgb but
> using only input colors that are within srgb gamut?

No, but I really do not suspect any difference in this case.

But what I will try some day is using POV-Ray as spectral renderer :)

This could be done within an animation loop of e.g. 31 steps in 10nm 
from 400nm to 700nm (I got inspired by Bruce Lindbloom who did exactly 
this with his own self-made renderer).
Some spectral data for fluorescent tubes is already part of lightsys and 
for the color definitions I can use my spectrophotometer and visit some 
of my former business partners for real world paint samples that do 
match the stage design.
Due the characteristic of fluorescent light sources (with its strong 
peaks instead a continuous curve) I do expect some interesting results.

-Ive

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