POV-Ray : Newsgroups : povray.beta-test : Difference between 3.6 and 3.7 in image : Re: Difference between 3.6 and 3.7 in image Server Time
19 Jun 2021 17:17:32 EDT (-0400)
  Re: Difference between 3.6 and 3.7 in image  
From: Warp
Date: 3 Nov 2011 05:13:20
Message: <4eb25b2f@news.povray.org>
clipka <ano### [at] anonymousorg> wrote:
> http://wiki.povray.org/content/Documentation:Tutorial_Section_3.3#Gamma_Handling 

  Btw, I think that the description of the first image is a bit lacking.
With which I mean it's a bit ambiguous.

  When it says "but the pigment is a mere 21.8% as bright as the rightmost
one. The true 50% brightness sphere sits right behind it" it's confusing
without a clarifying explanation of what it's talking about.

  It's the old problem with absolute brightness vs. perceived brightness
(iow. what the human eye sees as the brithness being). When that text uses
the numbers "21.8%" and "50%" it's talking about absolute brightness, iow the
amount of energy emitted by those pixels. However, most people don't realize
this and only think in terms of perceived brightness, iow. what they see.
In terms of the latter, the front row is (almost) linear while the second
row isn't.

  The problem with that is that people will tend to disagree with the
description. "What do you mean the sphere in the middle of the second row
is 50% bright? It clearly isn't. It's much brighter than that." Such a
disagreement, spawning from the ambiguous description, easily leads to
rejecting the whole concept of the new gamma handling.

  A technical description between absolute brightness and perceived
brightness, one which is easy to understand, and why this distinction is
important in randering, may be hard to write, but I think it's necessary
in order to avoid confusion.

                                                          - Warp

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