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D Fosse
Community Expert
D FosseCommunity Expert
Community Expert
July 4, 2019

Huh. That sounds crazy. I've done everything I can think of to test on my Eizo CG2730, but don't see any abnormal banding.

No, I can't get 30 bits to work now, but that's nothing new. That's been on and off forever. So I do see the individual 0-255 steps. But nothing special beyond that. I'd still trust this monitor absolutely for any critical work.

It's also very curious that Eizo firmly place the blame on 1903, but without anything to support the claim. If this happens on a hardware calibrated unit that doesn't rely on calibration LUTs, and the profiles are healthy - the prime suspect would naturally be a buggy video driver, not the OS. I'm not saying it couldn't happen, it's just unlikely enough that other factors need to be ruled out first.

My private suspicion is that someone at Eizo finally discovered the ProPhoto banding bug in OpenGL code. As it happens, this tends to get worse with table-based monitor profiles, which ColorNavigator makes at default settings. Switch to matrix, and most of it is gone. Switch to Adobe RGB instead of ProPhoto, and the issue vanishes completely.

(BTW, the gHacks piece seems to mix up two unrelated issues. Failure to load the calibration LUTs has nothing to do with banding, and it's not what Eizo is concerned about. They wouldn't be, it doesn't apply on Eizo ColorEdges).

    Y
    Yume-chan
    Participating Frequently
    July 24, 2019

    ColorNavigator profiles, like other ICC profiles generated by other HW calibration solutions after calibration, stores a linear calibration (no calibration) in profile's VCGT tag in order to clean any existing graphics card calibration.
    It's like other ICC profiles generated by GPU calibration suites like DIsplayCAL, but with a linear calibration.

    There is a bug in Windows 10 1903 that once you reload into GPU a calibration (load ICC profile VCGT tag contents into GPU LUTs) it shows this distinctive banding  with borad bands or steps.
    Suggested workarrounds include disable MS loader for GPU LUT on startup: if you assign an old ICC profile generated with ColorNavigator nd reboot/lonoff-logon there is no banding issue. It you change default display profile at OS level while in a Windows session it is going to reload whatever VCGT content it has to GPU LUTs... and suffer this kind of banding related to 1903.

    As some user reports with no GPU drivers (no vendor specific drivers) there is no bug because there is no access to GPU LUT.

    This bug is everywhere: AMD GPUs, nvidia GPUs, Dells, Eizos, HW cal, software CAL... try to load VCGT contents of a profile in GPU LUT result in banding unless you reboot or logout&login.
    Miscrosoft broke something related to GPU LUT loading.

    This bug also applies to traditional GPU calibration like DisplayCAL with GPUs that produce no banding in this setup (like AMD radeons with their 10+bit LUTs + dithering at output, among others). BUT, and this is important, if you do the workarround trick and disable scheduled task WindowsColorSystem on computer boot VCGT calibration contents of a ICC profile are loaded properly into GPU LUT, with no banding (DisplayCAL LUT loader des the job). But if you change display profile (so you load another calibration, even if it is linar) the bug is back. Hence when user changes default display profile in OS (control panel / color management) there is something triggered that acts like this scheduled task. If we or MS find a way to disable it we can make our calibration work as intended.

      Y
      Yume-chan
      Participating Frequently
      July 25, 2019

      Well, if that Eizo site example is representative, I have certainly never seen anything like that. If that happens in some circumstances, it's certainly not universal.

      I'll be back at my workstation in a couple of days, so I'll have a closer look then.

      Note that 1903 does seem to require a video driver update. No idea if it's related, just rule that out first.


      Updated to latest radeon drivers. It is still there if I change default profile for my display and reload its VCGT tag contents into GPU.

      MS broke something and it is not new.

      About 3-4 mayor W10 updates ago if display goes to standby, when it awakens MS is limiting/truncating LUT calibration correction to 8bit, even if GPU and its driver allows 10 or 12bit data in LUTs (if GPU has dithered outputs gradients are smooth as in a HW calibration). A truncated LUT in GPU to 8bit in a linear lut is still linear, so people with HW cal did not noticed it.

      Also MS own LUT loader (& third party like Basiccolor or XRgamma) truncates to 8bit VCGT contents since I cannot remember when, so people with GPU calibration needed a 3rd party loader to get smooth bandless non color managed gradients. The same as above, linear calibration truncated to 8bit is still linear so Eizo CG owners never noticed it, others did.

      The "funny" part is that MS never broke a linear LUT calibration before this 1903 issue... so now all monitor owners which use profiles with VCGT tags that get loaded into GPU suffer the issue. All of them, even those who paid a high end monitor with HW cal that generates ICM profiles with VCGT tags.
      So this is a SEVERE issue.

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