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Discussion Starter · #1 ·
As you know Windows incorrectly computes a linear VCGT curve as a result it uses 65280 max value instead of correct 65535. I was trying to fix it by using DispWin from Argyll but it's quite PITA, especially in multimonitor environment when you have to switch displays. And as a side effect, after correcting VCGT table your PC is no longer bitperfect (for example Calman's built in Dolby Vision pattern generator stops working). Is it worth to bother with it? I feel that differences during calibration between correct and incorrect VCGT are smaller than standard measurement error.
 

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Windows VCGT and X-Rite LUT Tester tool have problems to apply a correct UNITY LUT.

ColourSpace HTL can export a NULL (reset LUT) and then use SpaceMatch DCM (loaded during windows startup) to load a true NULL, an accurate bypass can be obdained using that method.

The next step is to measure 33-Point Grayscale, generate 1D LUT, export the VCGT and load it from SpaceMatch DCM.

If you have 2-3 monitors, you can define which VCGT to load per each model.
 

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Discussion Starter · #4 ·
I was using "dispwin" cmd tool from Argyll package with "-c" option which is described as: "Load a linear display calibration" and verified it with x-rite's "Calibration tester" and "DisplayCAL-curve-viewer.exe" tools which showed correct VCGT values. Anyway Calman's built in Dolby Vision pattern generator worked with improper Windows linear VCGT curve (65280) and didn't with true linear VCGT curve (65535). I'm curious if it will work with "SpaceMatch DCM" VCGT reset but don't expect success:)
And can SpaceMatch DCM handle monitor switching and resolution changes. After every monitor switching or resolution changes you have to set correct VCGT again. I was using dispwin on batch file added to windows autorun so after any monitor/resolution changes I have to remember to run batch manually. Finally I gave up.
 

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And can SpaceMatch DCM handle monitor switching and resolution changes. After every monitor switching or resolution changes you have to set correct VCGT again. I was using dispwin on batch file added to windows autorun so after any monitor/resolution changes I have to remember to run batch manually. Finally I gave up.
It's a windows issue; I have a shortcut to re-apply them after scaling changes to my system, a shortcut per each monitor.
 
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