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Re: Are gamma discrepancies relevant?
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Re: Are gamma discrepancies relevant?


  • Subject: Re: Are gamma discrepancies relevant?
  • From: Koch Karl <email@hidden>
  • Date: Fri, 03 Apr 2009 09:51:51 +0200

Hi all,

I´m glad that (nearly) everybody oagrees on what I wrote earlier, yet there obviously are still some doubts.

Am 03.04.2009 um 07:49 schrieb Marco Ugolini:

In a message dated 4/2/09 10:35 PM, Klaus Karcher wrote:

Marco Ugolini wrote:
I don't think any of this proves anything much about inherent advantages
accruing from the concordance of TRCs between the file and the monitor
profile: it only proves that a file will be subjected to the least possible
amount of potentially damaging transformations when...it effectively does
not undergo any transformations at all! That much I agree with. :-)

So we agree upon the statement that every conversion in 8 bpc leaves its
marks in the form of banding, missing steps and color shifts.

It creates the possibility of that sort of results, yes.
That´s all I ever meant to say ;-)
But "possibility" is very vague – if you want to be on the safe side, you want to avoid "possibilities" altogether.

The *actual* results will vary based on many variables, and banding is not a
*necessary* consequence in each and every instance. Still, it does happen
often enough to be a sizable concern.


(As the color spaces are not perceptually uniform, some of them are more
annoying than others.

Meaning just monitor profile spaces, or all color spaces, working spaces
included?
Even more so, when they interact – and they always do. If you display a file on your monitor, there are always working space and monitor space involved.


Along the gray axis we are particularly sensible
for those quantization artifacts. The larger the differences between the
encodings, the more artifacts will be visible.) The logical conclusion
for me is to avoid 8 bit transformations as much as possible, e.g. by
performing display calibrations or even colorspace conversions with
higher bit depths inside the monitor, by co-ordinating working- and
display TRCs -- or by widening the bottleneck of current display interfaces.

Again, I don't think that "co-ordinating working- and display TRCs" does
much to solve the problem, because it's a solution only in the absence of
vcgt curves, which always exist in monitor profiles.
But they are linear und thus innoxious if you have a hardware- calibrated monitor.


I agree much more strongly on the desirability and usefulness of on- board
high-bit monitor LUTs, or even ... heaven forfend ... high-bit display cards
in the CPU itself!
We´re on the way, if you look at the new Mac Pros. But there is still a long way to go. As a software manufacturer, I dread the consequences. As long as there is no established standard, and as long as we have a mixture of "old" 8bit and new high-bit graphic cards plus high-bit LUTs in Monitors, a general solution that suits all scenarios will be complicated to write – and thus so expensive that no one will be prepared to paythe price ;-)


You may say I'm a dreamer, but I'm not the only one... ;-)
… no, you´re not!


Marco


Karl

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References: 
 >Re: Are gamma discrepancies relevant? (From: Marco Ugolini <email@hidden>)

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