Thread: "16-bit" mode.
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Old November 27th 04, 08:42 PM
Mike Russell
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Mike Engles wrote:
[re alvy gamma article]

Hello

Yes there does seem to some confusion about PC Gamma, but he [Alvy] is
absolutly clear about the need for linear processing. As for not
understanding Gamma encoding, that is not clear from the article. He
has
been around a long time, and does know a thing or two. If gamma
encoding
were that important he would have mentioned it. He is totally clear
about not applying any non linearity to a image, just to the display
device. I assume from this he means the same for storage, but I don't
know.

Suffice to say that he and his collaborator are MAJOR digital graphics
imaging authorities who on the face of it supports Timo Autiokari's
lonely stance. His last words in the gamma article are telling.

Mike Engles


Right on. Alvy has another article, written in 1995, that goes into further
detail re gamma issues:
http://www.cs.princeton.edu/courses/...s/smith95d.pdf
.. In this 1995 article, Alvy states:
"Nonlinearity should never be stored in an image. Or, if it is, then this
nonlinearity must be noted in the storage format in such a way that it is
known how to remove it to retrieve linear data."

This comment, as fundamental as it is to graphics algorithms, plus others
relating to the concept of working versus display space, came years before
Photoshop 5 commercially introduced the concept of working spaces, as part
of color management. Not bad for someone who "doesn't understand gamma".

As for Timo's lonely stance - he appears to be in good company now, having
been debunked together with Alvy Ray Smith and Dan Margulis, all in the
space of a few days. :-)
--
Mike Russell
www.curvemeister.com
www.geigy.2y.net