"Tim Nikias v2.0" <tim### [at] gmxde> schrieb im Newsbeitrag
news:3edba08f@news.povray.org...
> [..]
> But perhaps I'm having a distorted perspective
> on gamma and monitors, and what I'm saying
> is complete crap... :-)
>

Sorry Tim, but yes -  thats complete crap!
But it really seems that the point of gamma correction is still
a mystery to so many Povers. So one more try to explain:
The gamma of a crt monitor refers only to the physical fact that a
cathod ray tube does not respond to the input voltage in a linear
way. This is not a matter of quality, this is just a simple fact.
It has nothing to do with the way pixels blend together (this
is significat for the sharpness) and also not with brightness and
contrast settings (both are linear and can be used to adept better
to the surrounding lighting condition). Typical values for crt's are
in the range of 1.8 to 2.7 so 2.2 is usual a quite good average
value.
Do NOT trust any visual test so much (like the well known gray
pattern test). The only way to get the execat gamma value is
measurement with a spectrophotometer or (much easier and
cheaper) have a look at the homepage of the manufactor of
your monitor.
But in fact, the exact value of your own monitor is less important
because the default gamma for windows/linux is 2.2 and as both
OS do no gamma correction every application that tries to handle
images has to handle gamma for itself and does usually also
assume a default gamma of 2.2. In the Mac world this value
is 1.8 and if you are lucky and work on a SGI machine you have
not to care at all because the operating system handles gamma
correction (and every application that runs there knows that).

So all is quite easy. If you are using windows or linux put display
gamma 2.2 into the ini file and mac users 1.8.
But when you try to exchange your image (show it on a web
page or in a newsgoup) I would say the compromise of 2.0 is
the best idea if you will finally use the JPEG format, but if you are
using PNG files you should use the setting that correspondent to
your OS as mentioned above because PNG is able to store the
gamma information and will display with every OS in the same way
(at least if the viewer application handles gamma correct - and not
every image viewer does).

In the professional world are usually file format used that are able
to include not only the gamma information but the complete icc profile
but this is a completly different story...

so long
-Ive

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