Question – Black clipping message on “auto” output while Full RGB is enabled

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  • #27674

    TheLostWanderer
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    Hi all,

    Yesterday, while trying to use displaycal, I got the message shown in attachment. I don’t really understand it because I checked that “full range RGB” is enabled in my driver settings (and I thought it was only a problem with HDMI). I never saw this message before because I usually manually tick “full range” for “output levels” instead of “auto”.

    I have a benq sw240 which I calibrated using PME (1.3.8, as I had issues with .11) in panel native, REL blackpoint, L120, G22. Displaycal settings are: correction LCD PFS Phosphor WLED IPS, …(HP DreamColor Z24x G2) / 6500K, white & black lvl as measured, G2.2, black output offset 100%, ambient light adjustment 120 Lux, black point correction 0, rate 4; calibration speed M (was the same with VF).

    Could this explain the color drift I always see at < 10% brightness on the attached reports? I also wonder if it comes from the REL blackpoint settings in PME (default is ABS), but I sometimes get weird reddish tint in the blacks when I use PME.

    Any feedback is appreciated!

    Stay safe and happy new year đŸ™‚

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    #27686

    Vincent
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    Contrast is abnormally low, unless some UC is prensent on display

    #27687

    TheLostWanderer
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    I am sorry if this sounds dumb, but what does UC stand for?

    #27691

    Vincent
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    Sorry, “uniformity compensation”. On low cost low quality displays color uniformity issues are common. If vendor wants to mitigate them it needs to lower max output of panel channels in some zones, hance contrast drops. The worse the uncompensated panel is, the more contrast will be lost.

    So, back to you. That low costrast may be caused by: some limited range issue like DisplayCAL reports or UC.

    If you are running DisplayCAL on top of PME HW calibration, maybe DisplayCAL is complaing about actual clipping caused by poor quality software, and PME is known to be that way. I meant, your monitor (its HW) may be able to calibrate well, but PME calibration (its results applied to your monitor HW) is causing clipping. If that is happening you may want to mode to some user/custom OSD preset and do full calibration in GPU & OSD gains rathar than PME first and then refining its not so good results in DisplayCAL.
    IDNK, try some black patches ranging from 0 to 30 in 1step increment in MS paint. Read them with ArgyllCMS spotread and see what happens to Y. I think that you can do it too with DIsplayCAL and some custom test chart in “measurement report” but I’ve never used it. Try to see if clipping happens depending on PME settings, then avoid PME settings that cause clipping if ypu plan to refien its results with DisplayCAL GPU calibration.

    #27701

    TheLostWanderer
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    Ok thank you for your detailed feedback, I will do as you propose and continue experimenting with PME and DisplayCAL over the next coming days.

    I have one additional question: atm, my system is configured to output 8bpc. Would switching to 10 bpc (8+ FRC) improve things? Maybe not so much because of FRC? Or barely/not at all given the fact that it is an entry-level monitor?

    #27703

    Vincent
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    It does not matter for PME. It does not and never will take exhaustive measurements.

    For displaycal & nvidia better to set 10bpc, otherwise nvidia driver will truncate calibration.

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