Jaap Frank <jjf### [at] casemanl> wrote:
> I'm curious Warp. I've shrunk the file you made yourself for the thread
> 'More Gamma Again' in p.b.i to a very small one. Now you don't have
> to see through your eyelids but can simple look at it. For me the 3.6 
> side is lineair and the 3.7 side absolutely not. How looks this stamp 
> on your monitor now?

  The purpose of the image was not to show that the gradient is linear,
but that the middle of the gradient corresponds to 50% brightness.

  In the original image there are horizontal lines alternating between
pure black and pure white, hence producing an overall brightness of about
half of pure white. In my monitor this 50% brightness of the sides
corresponds to approximately the middle of the pov3.7 gradient.

  Of course it doesn't *look* 50% bright because the human eye doesn't
perceive the brightness linearly.

  If you scale the image smaller, presumably by averaging pixels, you will
cause the sides to become (128,128,128) (as that's the average between
(0,0,0) and (255,255,255)) which does *not* correspond to 50% brightness.
It corresponds approximately to 50% *perceived* brightness, as seen by
the human eye, at least on monitors with a gamma of 2.2, but it doesn't
correspond to 50% *absolute* brightness, which is what the alternating
lines are producing.

  In my monitor the sides of the scaled-down image look significantly
darker than the sides of the original image.

> Don't say it's the thrinking technic, because for me it's absolutely 
> the same for the big and the small one.

  I really can't understand in which situation the gradient produced
by pov3.6 looks linear and, at the same time, the alternating pattern
looks like corresponding to the middle of that pattern. As far as I
understand, if the pattern would look about the same as the middle
of the gradient, the gradient should not look nowhere even close to
linear, or if the gradient looks linear, the pattern should not look
even close to being the same as the middle of the pattern. Unless the
white lines in the pattern are, for whatever unfathomable reason, narrower
than the black lines (hence reducing the overall brightness of the
pattern).

  I don't think it can be that the system is gamma-correcting what it's
showing on screen (so that the pattern would then match the center of
the gradient) because then the gradient would not look linear (it would
look like what pov3.7 produces by default).

-- 
                                                          - Warp

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