LG 31MU97 strange calibration…

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  • #14823

    Googloiss
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    Hi everyone, I’m having some strange issues with calibrating my LG 31MU97-z… I try to explain my situation: I have two monitor, an old HP w2207h (connected to a GTX 1070 via HDMI, I mainly use it for GUI during color correction) and a recently bought LG 31MU97-z (that I use as the reference monitor during color correction – and for this purpose it’s connected to a decklink mini monitor 4K via HDMI – and in normal desktop mode – for this purpose it’s connected to the 1070 via displayport). At the moment I work with Premiere Pro (further on I will probably pass to DaVinci).

    The first thing I did was calibrate both my monitor, I started with the HP and displaycal: everything ok I suppose (it’s an old cheap monitor, not for grading, so I didn’t expect too much), then I moved to the LG, and here things must be done carefully. I tried to do two different calibrations, one for the “color correction mode” and one for the “desktop mode”, so since the decklink completely bypasses the OS, I made that first calibration with true color pro, so that the resultant LUT could be stored in the monitor itself (which can bypass the OS, too) and selected with the decklink activated. Here I had the first problem, although it doesn’t concern displaycal… (in short: the 31MU97-z has the possibility to store two custom calibrations using true color pro, but every time I make a calibration, it is stored in both monitor’s slots, I can’t store two different calibrations… and I don’t understand why… But let’s go on)

    The second calibration of the LG, the one for the “desktop mode”, I wanted to make it with displaycal, to have more accuracy, so I selected “User” in the picture mode of the monitor (in order to set RGB values on my own), and I went on with displaycal, I think I’ve set everything correctly, I chose to do the longest calibration (with the four hours of patches), and then I finally had my profile without any error, but it was like that: (see the attachments…)

    Obviously there’s something wrong, but I don’t know what it can be, on the HP I didn’t have similar issues, and the settings were almost the same… Any help? Thank you for the support!

    (p.s. I apologize in advance if my english isn’t correct, I’m italian)

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    #14827

    Florian Höch
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    Hi,

    make sure that you disable the monitor internal 3D LUT for profiling, and any automatic dimming/contrast/power saving functionality it may have. The measurements look like your monitor is not stable over time at all. Reduce the number of profiling patches to a sensible amount (anywhere from 175 to 1500), enable white level drift compensation to try and counteract display drift.

    #14828

    Googloiss
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    Thank you Florian for the timely reply!

    I disabled the automatic brightness dimming and power saving functionality, but the fact is that you have to select something in the picture mode list, there are: sRGB, Adobe RGB, DCI-P3, Calibration 1 and 2 (those made with true color pro), and User, with User selected all the settings are editable (unlike the other picture modes), except for the black level, that is locked due to the displayport connection (the manual says it’s a HDMI-only feature…), then you can independently set the brightness, contrast, sharpness, response time, gamma, color temperature (in kelvin degrees or in RGB values), tone and saturation of  red, green, blue, cyan, magenta and yellow. With all these settings, I left them as they were by default, I changed only the brightness and the color temperature (with the RGB values) in order to proceed with the interactive calibration of displaycal.

    This monitor has a lot of manually editable settings, I don’t know if maybe they come into conflict with displaycal, is there anyone here that has successfully calibrated this monitor with displaycal? (Not for DaVinci)

    In the meantime I try another calibration with less patches, even if I don’t understand why this could be my problem, since displaycal allows such a deep and long calibration, I wanted to make it to have the most accurate result…

    #14831

    Googloiss
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    Ok, I made a new calibration disabling for sure all the automatic settings of the monitor and selecting an amout of patches of about 3500, and this time it seems to be fine, I attach the zip and png files for a match, let me know if everything is ok, thank you!

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    #28323

    Niklas Ladberg
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    Hi! I have the exact same LG monitor and use it for color grading after DisplayCal-calibration. Could you walk me through the settings you set in the monitor prior to DisplayCal to get the best result in your last post?

    #28333

    Googloiss
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    Hi Niklas! I’m sorry to tell you that at the end of the story I’ve left displaycal for this monitor and went only with its native calibration software which can interface directly with the monitor hardware… Now I use displaycal only with my old secondary monitor.

    #28334

    Niklas Ladberg
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    OK! I assume you got better result that way, any learnings regarding that process you would like to share?

    #28335

    Vincent
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    LG HW calibration software has no support for LG 31MU97-z backlight (it never had)… although since its a GB-LED the wrong RGB LED correction used by LG will not make a huge error in white point.

    #28336

    Niklas Ladberg
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    Thank you Vincent. Do you know which way is the best to calibrate this monitor? I have not achieved perfect result (but pretty good) with Displaycal, but maybe I choose the wrong type of monitor in displaycal (do you know which type I should choose?) or is it better with using the LG HW calibration?

    #28338

    Vincent
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    LG software as many other (Benq, Dell for some models, etc) are partually faulty using colorimeters because manufacturer did not include colorimeter correction for their backlights. They use a wrong one, RGBLED, for all their widegamut models, yours or newer P3 only multimedia displays.
    In your case 31MU97 is a GB-LED. Proper correction will be GB-LED/RG_phosphor. They are bundled with displaycal in Dell_U2413_25Jul12.ccss (pure) or RG_Phosphor_Family_25Jul12.ccss (mixed with other backlights). There are also user made cotrections at worse spectral resolution in displaycal colirimetr database (but some are faulty, sRGB emulation).
    Since it’s a GB-LED, error is expected to be low on a typical well behaved i1d3 colorimeter. But check it.

    -Run True COlor Pro (or whetever name it has now), calibrate to D65 in Rec709 or native gamut, let it make profile.. etc
    -Run DisplayCAL, measurement report, no simulation profile. Make sure you use one GB-LED correction for colorimeter. Canonical GB-LED correction may be Dell_U2413_25Jul12.ccss
    -on resulting HTML report check “meassured white to assumed white” (distance to closest “natural” white in cool-warm axis) and “measured white vs profile white” (distance between actual white and the white that supposedly measured LG software).
    Check contrast too, native typical 1000:1, >800:1 is expected for D65.

    If results are good you can use True Color Pro (TCP) as a basis even with its measurement limitations. Some examples:
    -calibrate in TCP to Rec709 gamut, 2.4 gamma, d65, 100cd. Use that calibration for your video work in color or not color managed apps
    alternative:
    -calibrate in TCP to native gamut (full), d65. Use that calibration as a base for making LUT3D for resolve (with DIsplayCAL) or whetever you do, but this need to use color managed software.

    If TCP calibration shows bad grey color (a*b* range vs true neutral grey) use DisplayCAL on top of HW calibration to correct it, in any of the two alternative samples above

    If TCP calibration acts weird whith huge assumed vs measured white errors, or destroys contrast 600:1 or something too bad, use DisplayCAL only.

    Summary:

    test TCP, validate its results with DisplayCAL and a GB-LED correction

    • This reply was modified 11 months, 3 weeks ago by Vincent.
    • This reply was modified 11 months, 3 weeks ago by Vincent.
    #28343

    Niklas Ladberg
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    Vincent, wow, thank you! I will try tomorrow.

    #28366

    Niklas Ladberg
    Participant
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    Hi Vincent!  I got best resultat with DisplayCAL on top of HW with 1d3 and Your suggested settings. Attached result with 172 in brightness. Maybe could get a bit better results with lower brightness. But I think it would be too dim. Does this result seem resonable? Seems ok to my eyes.

    Is there monitors that are brighter and a lot better for grading than this LG  (32” or larger) that is cheaper than Eizo-pricelevel?

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    #28374

    Vincent
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    Hi Vincent!  I got best resultat with DisplayCAL on top of HW with 1d3 and Your suggested settings. Attached result with 172 in brightness. Maybe could get a bit better results with lower brightness. But I think it would be too dim. Does this result seem resonable? Seems ok to my eyes.

    Is there monitors that are brighter and a lot better for grading than this LG  (32” or larger) that is cheaper than Eizo-pricelevel?

    It won’t be too dim, it’s just your enviromnet that is too bright.

    Also calibrating to L* for grading is mostly useless, ICC based vidoe editors or LUT3D based video editors will undo it. Choosig rec709 TRC for monitor TRC is 99.99999% of time a mistake.

    Also missing grey range check & WP to evaluate how good is HW cal.

    #28375

    Niklas Ladberg
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    Thank you Vincent! The purpose is for colorgrading in Resolve (mainly for internet, but sometimes TV commercial). What settings did I set wrong in hardware cal and/or displaycal? (I do not know what L* is . )

    #28376

    Vincent
    Participant
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    If results are good you can use True Color Pro (TCP) as a basis even with its measurement limitations. Some examples:
    -calibrate in TCP to Rec709 gamut, 2.4 gamma, d65, 100cd. Use that calibration for your video work in color or not color managed apps
    alternative:
    -calibrate in TCP to native gamut (full), d65. Use that calibration as a base for making LUT3D for resolve (with DIsplayCAL) or whetever you do, but this need to use color managed software.

    If TCP calibration shows bad grey color (a*b* range vs true neutral grey) use DisplayCAL on top of HW calibration to correct it, in any of the two alternative samples above

    If TCP calibration acts weird whith huge assumed vs measured white errors, or destroys contrast 600:1 or something too bad, use DisplayCAL only.

    Summary:

    test TCP, validate its results with DisplayCAL and a GB-LED correction

    Since you chose the 2nd one, then in DisplayCAL choose the closest gamma/TRC to whatever you put in True Color Pro. Since you aim for native gamut and then correct all to video content colorspace, then choosing 2.2 gamma for both (TCP + DisplayCAL) seems a reasonable (versatile for a lot of content, image editing, printing, color managed video) choice although there are others.

    Then make LUT3D for Resolve with source Rec709 colorpsace and 2.4. There are a lot of threads withthe same questions. Look for one a week ago by irfan and his SW2700PT.

    • This reply was modified 11 months, 3 weeks ago by Vincent.
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