"Bruno Cabasson" <bru### [at] alcatelaleniaspacefr> wrote:
> > The colors are all simple, rgbf values like 1,0,1,0.5
> > In particular, the blue is <0,0,1,0.5>
>
> Hello Dave.
>
> Perhaps I am wrong, but I can see 2 reasons why color rgb <0,0,1> looks
> darker than <1,0,1>:
>
>     -) <0,0,1> carries half the 'energy' of <1,0,1>. To be comparable in
> brightness, the 2 colors you mentionned should be of equal energy (use
> vnormalize)
>
>     -) the human eye does not perceive the whole spectrum with the same
> intensity: with the same magnitude, a green color looks brighter than red
> and even brighter than blue.

It's even more so then that. POV uses the standard for grayscale conversion,
which is based on real light energies

GRAY = 0.3*R + 0.59*G + 0.11*B

RGB<0,0,1>=0.11
RGB<1,0,1>=0.41
almost 4 times the apparent brightness


-tgq

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