Christian Froeschlin <chr### [at] chrfrde> wrote:
> I have to admit I don't understand this either. Until now I
> thought that since 3.7 now uses a linear color space, 0.5 would
> represent a true midgray and all the nifty gamma handling ensures
> that everyone perceives that midgray on their display when viewing
> the image file. So I'd also have expected the end result of your
> test scene to visually yield evenly spaced brightness steps.

  Well, there's a traditional test to see if rgb 0.5 (as produced by
POV-Ray 3.7) is equivalent to half-brightness of your display: Make
an image which is 0.5 gray all over, and another which has horizontal
lines of pixels alternating between black and white. Put these two
images side-by-side and then watch them from far enough that you don't
distinguish the individual lines in the second image. Compare the
brightness of the two images. Make the same test with a rgb 0.5 image
produced by POV-Ray 3.6.

  When I made this test, POV-Ray 3.7 produced approximately the proper
brightness (the two images looked very similar from far away), while
POV-Ray 3.6 produced an image which was *clearly* darker than the
alternating-lines test image.

  Now, if you do make a gradient from black to white with POV-Ray 3.7,
the transition doesn't look linear for some reason, even though the
midpoint has exactly the correct brightness to be 50% gray. I don't know
what causes this.

-- 
                                                          - Warp

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