[argyllcms] Re: Display LUT depth and Gamma
- From: Graeme Gill <graeme@xxxxxxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Fri, 23 Dec 2011 09:56:08 +1100
Philip Reed wrote:
> My question is this: Does setting the RGB levels to anything less than 100
> limit the available color palette? I seem to recall reading that lowering
> the setting for green (as an example) reduces the size of the internal LUT
> for that channel. Is this based on bit depth? I can see how it may
> compress the available steps.
Hi,
it depends on how the display adjustments are implemented. Conceptually
they could reduce the bit depth, or they might not. If you make the same
adjustments
in the video card (vcgt), then it will certainly reduce bit depth though.
Unfortunately manufacturers technical data tends to be very limited, so
it's hard to determine what they do in practice.
> Given this monitors settings, would it be just best to set it to "Standard",
> adjust brightness and then profile?
There's a better chance of preserving bit depth if the display controls are
used, since they at least may have access to greater depth, whereas DVI
is limited to 8 bits/component.
> I work in a dark room and when I run "Report on Uncalibrated Display" get a
> gamma of 2.0. My choice of settings is color temp. 6500K, white level 120,
> black level: 0.13 and gamma 2.2. The results look excellent but if I run a
> "Report on Calibrated Display", the gamma is 2.8. Can someone explain this?
> Is this indicative of what people refer to as "crushed blacks"?
Don't read too much into the gamma numbers, as the measurement of gamma
is very dependant on the black levels, although the discrepancy seems
unusually large (you might want to check that you aren't seeing changed due
to display warm-up). No, I don't think this has anything directly to do with
"crushed blacks". The latter is typically to do with clipping at the black
end.
Graeme Gill.
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