Xrite Color Profiles ?

Started Aug 7, 2021 | Discussions thread
Iliah Borg Forum Pro • Posts: 28,899
Re: Xrite Color Profiles ?

Jack Hogan wrote:

dddduuuu wrote:

Iliah Borg wrote:

dddduuuu wrote:

Iliah Borg wrote:

dddduuuu wrote:

Brightness 50, Blacks 5, Contrast 50 and Curve Medium Cobtrast makes ACR pipeline true linear.

You got it exactly wrong.

Here is our artice that explains the issue https://www.rawdigger.com/howtouse/overriding-raw-converter-default-adjustments-settings

you've missed the main point.

Try your setting instead without modifying the dcp to make the embedded curve (0,0) (1,1) and prove the resulting numbers for G with gamma 1 form a linear progression, increasing 2x per stop.

If DCP-profile doesn't have ProfileToneCurve tag, ACR applies the default one


To embed a linear curve into an existing profile, I use a very fast, reliable, and simple method:

> exiftool -ProfileToneCurve="0 0 1 1" -o new.dcp old.dcp


Are you suggesting that a user does the above (as in my comment to the article)? If so, IMHO you should have explained it explicitly, starting with what is "linear profile" in your "Just reset, then select linear profile and PV2. "Zero" of some adjustments is set with non-zero value. Brightness 50, Blacks 5, Contrast 50 and Curve Medium Cobtrast makes ACR pipeline true linear" and how to make one.

Iliah, i've made some research to explain you more clearly what I mean.

I downloaded raw image of studio shot on Nikon 4DS with ColorChecker24 and made some measurements and calculations. You can examine that measurements by yourself.

Here some results:

1. Max DE with your settings for linear process (profile Adobe Standard, Process Version 2, Blacks 0, Brightness 0, Contrast 0, Curve Linear) is 11,06.

2. Max DE with Adobe Linear profile and default (non-zero) settings (profile Adobe Linear, Process Version 2, Blacks +5, Brightness +50, Contrast +25, Curve Medium Contrast) is 6.61. Colors of gray patches exactly the same as with previous settings. But color patches are more close to reference values.

3. I've made the most simple profile Adobe ColorMatrix with only four image-related tags ColorMatrix1, ColorMatrix2, DefaultBlackRender and ProfileToneCurve. Only 22 numbers. Settings: Process Version 2, Blacks +5, Brightness +50, Contrast +25, Curve Medium Contrast. Max DE 6.52, very close to Adobe Linear. Just interesting.

Those are fairly bad.

To @2, standard Adobe matrices are interpolated in the process

Additionally, measurements of DPR target are not published, so the basis of deltaE calculations isn't well-established. A matrix calculated using spectral measurement of the target usually results in lower deltaE than a matrix calculated from averages, but in some cases it's vice versa, the difference can be 2 deltaE easily, for a couple of cases I checked it was 4 in favour of Adobe. One more thing: the spectrum of light DPR are using isn't published too. And a side note: to check Adobe matrix one should apply calibration matrix too (not the case with Nikon cameras).

With a linear rendition you should be getting about half that


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