clipka <ano### [at] anonymousorg> wrote:
> => The left stripe typically /looks/ linear, while the right strip 
> typically /is/ linear.

  As I have been discussin in length in this thread, the definition of
"linear" is a bit ambiguous.

  You can say that the right strip "is linear" (at least on a monitor with
the traditional gamma of 2.2) in the sense of radiant flux: The physical
amount of light emitted, when measured in watts. In other words, if you
counted the photons that are emitted by the right strip, this amount would
grow (approximately) linearly as we go down the strip.

  However, while it may be linear in a physical sense as described, it's
not linear in a *practical* sense. It's not linear as perceived by the
human eye, nor is it linear when looking at the pixel values.

  The radiant flux approach ought to give more realistic results when
calculating the illumination of surfaces (ie. how much they reflect light,
this "how much" being, precisely, the amount of radiant flux that the
surface emits). However, it poses a practical problem when the user tries
to create things like gradients that *look* linear, as perceived by the
human eye. This practical problem is only aggravated by the fact that most
people are already accustomed to programs handling brightness in terms of
perceived brightness (rather than radiant flux), as well as the fact that
pixel values map almost linearly to perceived brightness as well (at least
on gamma 2.2 monitors).

  This will cause confusion. However, I'm not sure what the best solution
to this would be. (Things like the 'srgb' keyword and 'poly_wave 2.2' for
maps might help, but there are probably still tons of other situations
where such practical problems might arise.)

-- 
                                                          - Warp

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