Huge Delta E – BenQ PD2700U

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  • #37829

    Bastien
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    Hi,

    I am trying to  calibrate my monitor according to the following steps :

    Resolve w/ DisplayCal – UltraStudio 4K Mini – BenQ PD2700U

    DisplayCal settings : Custom Rec.709 Gamma 2.4, 120cd/m2, 6500K (screenshots attached)

    As a result I get a delta E value of about 4 (average) and 19 (maximum).

    The verification data (PDF attached) is saying that my result is “not OK”, which may be the reason of those results.

    This 500€ monitor is supposed to cover 100% Rec.709 on the paper.

    Can you help me about this ?

    Thank you for your support !

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    #37834

    Kuba Trybowski
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    There’s nothing wrong with your display.

    The calibration failed because you set the colorimeter correction to Auto (None).

    You must select the right correction for the display’s backlight technology.

    According to this thread, you probably should start by using the “LCD White LED Family” correction:

    Measuring a wrong whitepoint

    #37835

    Vincent
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    There’s nothing wrong with your display.

    The calibration failed because you set the colorimeter correction to Auto (None).

    You must select the right correction for the display’s backlight technology.

    According to this thread, you probably should start by using the “LCD White LED Family” correction:

    Measuring a wrong whitepoint

    <iframe width=”474″ height=”267″ class=”wp-embedded-content” sandbox=”allow-scripts” security=”restricted” title=”“Measuring a wrong whitepoint” — DisplayCAL” src=”https://hub.displaycal.net/forums/topic/measuring-a-wrong-whitepoint/embed/#?secret=7XBqQeoG4z&#8221; data-secret=”7XBqQeoG4z” marginwidth=”0″ marginheight=”0″ scrolling=”no” frameborder=”0″></iframe>

    That’s not what is happening here.
    No correctrion means the measurements are wrong “against a reference”, not against itself (in calibration “none”, in verification “none”).
    A wrong correction (or no correction) will cause display to be off “vs reality” but measuring with the same wrong correction used for calibration it will measure OK.
    That’s how LG and Benq (& more companies) fool owners with their faulty HW calibration software.


    @Bastizor

    Hence if validation fails against a “wrong settting” but calibrated with same “wrong setting”  it could be:
    -monitor controls modified after calibration (display profile does not match current display behavior)
    -some kind of double calibration: VCGT in GPU and same VCGT applied in LUT3D.
    -wrong params in LUT3D creation

    but with provided data, who knows…

    Since measured gamma is ~2.2 and it is applying a device link to 2.4… i would say that some settings have changed in monitor or that a 3rd party app is lowering gamma. Check this.

    Also before venturing into LUT3D adventures, make a desktop profile display, validate it against itself (no simulation profile). Once this works so you have not messed up other things you can make LUT3D and load it into Resolve. For a GUI display you can use the same profile as destination.
    Also apply White LED correction as Kuba said.

    #37836

    Bastien
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    Thank you for your help !

    I have made another calibration with the White LED correction applied and the same other settings.
    The monitor is correctly set to gamma 2.4 (as it was already on the previous tests).
    The video signal is processed threw the UltraStudio 4K Mini so the GPU shouldn’t interfere in the results (if I understand correctly the purpose of this I/O device).

    The result is the following : average 4.89, maximum 19.43.

    The verification process with no simulation profile gave me the data attached below.
    I don’t know how to interpret those results as the gamma is showing ~ 2.8 which is quite weird at first glance.

    I am also trying to understand how DisplayCal and calibration work in general as this is my first attempt to properly calibrate an external monitor via an I/O device within Resolve.
    This would be my main preview monitor, my MacBook Pro being used for the GUI.

    Let me know if something looks wrong or if any other test could help investigating further about my case,
    Thanks a lot for your support !

    • This reply was modified 2 months ago by Bastien.
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    #37842

    Vincent
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    Your are not profiling display (desktop display) you are profiling it through resolve on macOS which is not what I asked. I’d say that you have enabled Apple’s color management engine on Resolve + some other app or feature raising the gamma.

    Profile display as desktop display with typical settings: D65, g2.2 and whetever nits you need. Validate it.
    Then you can use OS color management on resolve OR (exclusive or) create a LUT3D based on your desktop calibration (al calibratin settinsg to as measured) without VCGT.

    #37843

    Vincent
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    Oh, i did not read it before, you are not using it thorugh computer GPU but through another (device UltraStudio 4K Mini).
    Make sure that you have disabled Apples color management on Resolve.

    Validate display against displays own “uncalibrated” ICC, or against a reference (use simulation, use simulation profile as display profile). This will show you actual display behavior through Resolve. It will show display + ultrastudio behavior “as is”.  Check gamma and gamut boundaries. Maybe you are messing with OSD controls.

    I’d test the same but plugged to your laptop GPU, to discard some misconfiguration of your IO device for Resolve sicne we do not know what you have done to its configuration.

    #37844

    Vincent
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    Your are not profiling display (desktop display) you are profiling it through resolve on macOS which is not what I asked. I’d say that you have enabled Apple’s color management engine on Resolve + some other app or feature raising the gamma.

    Profile display as desktop display with typical settings: D65, g2.2 and whetever nits you need. Validate it.
    Then you can use OS color management on resolve OR (exclusive or) create a LUT3D based on your desktop calibration (al calibratin settinsg to as measured) without VCGT.

    That will work for a GUI, not for your setup, as I wrote above, I did not read that you were using UltraStudio 4K Mini

    #37845

    Bastien
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    Indeed, I a using the UltraStudio 4K Mini to bypass Apple’s color management.

    I will test the display against this own configuration if I manage find the proper settings.

    The only thing that Inhave set on the box is the resolution. But I will check again if there is anything wrong somewhere.

    Thank you for your expertise !

    #37848

    Bastien
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    I have done a verification test with the following settings :

    ✅ Simulation profile : Rec709 ITU-R BT.709
    ✅ Use simulation profile as display profile
    Tone curve : Custom (Gamma 2.4, Relative, Black output offset 100%)
    ❎ Device link profile

    Below are attached some screenshots of the settings applied (Resolve, Desktop Video Setup, DisplayCal) as well as a PDF of the results of the verification.

    Let me know if you need further information or if I have done anything wrong,
    Thanks a lot again !

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    #37853

    Vincent
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    Ok, this seems right on gamma with typical errors due this monitor being a little bigger than sRGB on green. Grey is somehow neutral out of the box. Good.

    Given this situation profile display without calibration and verify it against itself (no simulation profile). It SHOULD validate OK: profile will store actual R G B primaries coordinates and actual Gamma = custom profil  matches display behavior
    If it does not, check that resolve confing is not using Apple color management active, I do not remember the checkbox name.
    Since it will not be applied to OS settings, you can use compex XYZLUT profiles.

    Once you have a match between a display profile and display behavior, then you can create a LUT3D (source Rec709 g2.4 offset 100%, destination custom display profile) and load it to Resolve.

    Remember that  if you have a LUT3D in resolve and you are using Resolve’s output you should not use a device link in validation, because it will apply LUT3D twice.
    Device links are akin to LUT3D in ICC ecosystem. We apply device links in DisplayCAL when our output cannot apply a LUT3D. If a video output is applying a LUT3D you dio not use device link, you just put simulation profile & use display profile as simulation profile.

    #37854

    Bastien
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    Thank you for your feedback !

    Ok so I have to make a profile without calibration :
    Does it mean that I have to set white point, white level and tone curve to “as measured” in the calibration settings, and then make a profile from that ?

    I am not yet using a 3D LUT inside Resolve. I am currently trying to create one to apply to the “Video monitor lookup table” in the Resolve settings, the one that should adjust my display to properly reproduce Rec.709 Gamma 2.4.
    So if I understand correctly, I use the “device link” in validation when  there is no Resolve 3D LUT applied on the output. But in this case, I shouldn’t use it as I will apply a 3D LUT in Resolve output before the validation test, right ?

    Thank you for your precious support !

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    #37858

    Bastien
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    @Vincent

    So I have made a profile with the settings listed above.

    I have made a verification test with “no simulation profile” applied.
    I have found that clicking on [alt] can make a “self check report”. I don’t know if that’s what you mean by “verifying it against itself” so I have also made a “measurement report” as I did in the previous validation tests.

    You can find the profiling result and both verification data files attached below.

    Thank you again Vincent !

    • This reply was modified 2 months ago by Bastien.
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    #37865

    Vincent
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    So if I understand correctly, I use the “device link” in validation when  there is no Resolve 3D LUT applied on the output.

    It is the opposite, if you do not have a LUT3D in Resolve but you want to validate like you have one, you have to use device link. It’s not auto, its your selected configuration in DisplayCAL & Resolve.

    #37866

    Bastien
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    Yes that’s what I mean : I use the “device link” in validation when there is no 3D LUT applied in Resolve 3D LUT to simulate one as if it was applied in Resolve.

    Sorry if I am unclear in my wording.

    #37867

    Bastien
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    Given this situation profile display without calibration and verify it against itself (no simulation profile)

    As you may have already seen, I have made other tests/calibrations but I suppose those are wrong.

    Could you please elaborate on the sentence above ?
    I think I haven’t understood correctly what I should do from the last step that said was “good”.

    Thank you again Vincent !

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