Re: Are gamma discrepancies relevant? [was: UGRA/UDACT-conforming displays]
Re: Are gamma discrepancies relevant? [was: UGRA/UDACT-conforming displays]
- Subject: Re: Are gamma discrepancies relevant? [was: UGRA/UDACT-conforming displays]
- From: Marco Ugolini <email@hidden>
- Date: Thu, 02 Apr 2009 19:44:59 -0700
- Thread-topic: Are gamma discrepancies relevant? [was: UGRA/UDACT-conforming displays]
In a message dated 4/2/09 6:00 PM, Klaus Karcher wrote:
>> In a message dated 4/1/09 4:56 AM, Thomas Holm/pixl wrote:
>>> My experience tells me that you will see various degree of banding
>>> especially, in the two windows with a tone curve/gamma setting
>>> workspace which is different from your monitor calibration.
>>
>
> Marco Ugolini wrote:
>> Sorry, but I don't agree that this test actually provides incontrovertible
>> evidence of the theory's validity.
>>
>> Disclaimer: my monitor does not have a built-in LUT.
>
> Ok, here is another experiment that eliminates the influence of the
> video card LUT and other possible sources of error:
Klaus,
When you activate AdobeRGB as the display profile (not that anyone should do
that, but just for the sake of this exercise), the AdobeRGB file effectively
undergoes a *null* conversion from working space to monitor profile. That is
the best possible scenario, obviously, since it forces no transformations
whatsoever of the file numbers to a different set of converted numbers in
the monitor profile. Therefore, no errors occur due to necessarily imperfect
calculations within an 8-bit scenario. Also, no vcgt curves are applied,
which leaves the video input exactly equal to the video output. The results
are optimal -- exactly as smooth and pristine as the file itself is.
Similar ideal results ensue under the scenario of AppleRGB set as the
monitor profile: since ProPhoto RGB is also a 1.8 gamma profile, the neutral
grayscale ramp undergoes a null conversion to the AppleRGB monitor profile
in both the AppleRGB and the ProPhotoRGB file. (The grayscale ramp undergoes
*no changes whatsoever* when converting to and from AppleRGB and ProPhoto
RGB, no matter how many times you go back and forth. The numbers in the file
never change at all. For all intents and purposes, a *null* conversion.)
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. :-)
Marco
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