RE: Display Gamma: Factory vs calibration vs working space
RE: Display Gamma: Factory vs calibration vs working space
- Subject: RE: Display Gamma: Factory vs calibration vs working space
- From: "michael shaffer" <email@hidden>
- Date: Wed, 17 Nov 2004 14:01:31 -0330
- Importance: Normal
Danny Pascale writes ...
> You will find the answer to your question in the following
> document (which is the 1st version of the PNG spec but
> which has good info on gamma):
>
> http://www.libpng.org/pub/png/spec/1.0/png-1.0-w3c-single.html.gz
>
> You should also look at the following thread on the same
> subject going on a Rob Galbraith forum:
>
> http://www.robgalbraith.com/ubbthreads/showflat.php?Cat=&Number=28
I don't believe the answer need be as complicated as would need reading
these documents ... altho it is good reading. (see below)
> On Wed, 17 Nov 2004 11:12:46 -0500
> "amadou diallo" <email@hidden> wrote:
> > The Eizo LCD is factory adjusted for 0-255 steps in a
> >2.2 gamma. I've calibrated the monitor to a 2.2 gamma
> >(6500k and 95cd/m). When creating b/w gradients in both
> >RGB and grayscale modes, PS working spaces with 2.2
> >gammas display with absolutely no banding. Work spaces
> >with gammas of 1.8 and 2.0 (custom) both show slight
> >banding towards the shadow end. AGP card is nvidia
> >geForce4 MX. My understanding has been that hardware
> >gamma, calibration gamma and Ps wk space gamma do not
> >have a direct relationshiop and certainly don't need to
> >be identical. What exactly is the relationship between
> >these 3 values? And why, with a 10bit LUT would working
> >space gamma changes introduce banding?
These gamma settings do not need be identical, and PS will compensate for
their differences. However, imagine if all compensation was only 8bits
precise. That is, imagine a monitor's factory (hardware) gamma was 2.5, ...
and then you asked for calibration to set your monitor at 1.8 ... and then
you used AdobeRGB as your working space (2.2). This would involve 2
relatively large 8bit compensations and would most likely exhibit banding
(your monitor's mileage may vary). A 10bit LUT used for calibration would
make one of these compensations more precise ... or you could ask your
calibration software to calibrate your monitor for gamma=2.2, which would
help as well.
hth & cheerios ... shAf :o)
Avalon Peninsula, Newfoundland
<www.micro-investigations.com>
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