Reddish and greenish whites after calibration?

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  • #36225

    Antonio Marcheselli
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    Thanks.

    Then, accepting the risk to be blasted by Vincent, this could be “metameric failure” (thanks Vincent). You will have to use one of the calibrated monitors as a reference, then try to match the white manually using the tool I mentioned above. Once you are happy, DisplayCAL will take a reading and will profile and calibrate the monitor based on that white. It won’t read 6500K but that is ok.

    Also bear in mind that it will be difficult if not impossible to match those two monitors perfectly, it all depends on the spectrum of the light source. DisplayCAL will do its best but physics laws can’t be broken 🙂

    I hope this helps and I hope Vincent agrees with me on this! 🙂

    #36226

    Vincent
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    Regardless though, the issue is the same no matter what correction I use.

    Check if correction is causing an offset to measurements compared to other correction and to no correction.

    ns1208

    Can you confirm that when you say that your white and grey have red/green tints you mean that when you put your monitors side by side and display a greyscale, the whole greyscale looks reddish on a monitor and greenish on the other?

    Thank you!

    ns1208
    Can you confirm that when you say that your white and grey have red/green tints you mean that when you put your monitors side by side and display a greyscale, the whole greyscale looks reddish on a monitor and greenish on the other?
    Thank you!

    Yes that’s exactly what happens.

    If your grey was neutral, your later claim about grey was meaningless. It is expected that if white do not match grey won’t match.

    But your grey is not neutral in 27″, it has a mild color cast as reported by TRC (by some over/undershoot error on display, noise or because it is actually not neutral). Same in 24″, smaller but more extended. That is solved by do not using high speed but medium or slow.
    A measurment report with detailed greyscale patches may shed more light on severity (a*b*) than to spot these issues on a tiny TRC graph or a raw ti3 file.

    So let’s say that you recalibrate and after this process you have good neutral grey (by visual inspection or measurement report). If WLED PFS correction is not a good match to your 27″ display… you’ll need an spectrophotometer (use high res mode on Xrite one), or use visual whitepoint editor.
    1st one can be used when correction does not match actual SPD in display but gives you accurate whitepoint coordinates… but it cannot solve metameric failures because your observer do not match std observer.
    2nd one can be used in the same situation (missing proper CCSS) and when there is a metameric failure vs std observer and you but does not give you accurate coordinates on whitepint for profile. This means that you CANNOT use absolute colorimetric when making LUT3D on a visually matched white, you need to use relative whitepoint. Keep this in mind if yo want to use LUT3D in madVR ior DWMLUT.

    • This reply was modified 2 weeks, 4 days ago by Vincent.
    • This reply was modified 2 weeks, 4 days ago by Vincent.
    • This reply was modified 2 weeks, 4 days ago by Vincent.
    #36230

    Vincent
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    Thanks.

    Then, accepting the risk to be blasted by Vincent, this could be “metameric failure” (thanks Vincent). You will have to use one of the calibrated monitors as a reference, then try to match the white manually using the tool I mentioned above. Once you are happy, DisplayCAL will take a reading and will profile and calibrate the monitor based on that white. It won’t read 6500K but that is ok.

    Also bear in mind that it will be difficult if not impossible to match those two monitors perfectly, it all depends on the spectrum of the light source. DisplayCAL will do its best but physics laws can’t be broken 🙂

    I hope this helps and I hope Vincent agrees with me on this! 🙂

    That may or not may not be the cause.
    You cannot say that his WP issues are caused by metameric failure because you do not know Pixio Px277 spectral power distrubtion. We guessed (by probability) one of the known LED tecnologies and applied them (QLED maybe). There are more, some of them are not even bundled in default set for CCSS corrections for i1d3, like: https://i0.wp.com/palomakiconsulting.com/wp-content/uploads/2018/03/Figure-6-pixel-spectra.png?w=751

    But YES, as you said visual matching to a reference device is a solution. OP must remember to do not attpemt to use absolute colorimetric when making LUT3D for that display or matching will be undone. Visual matching is always a solution (all image editors use relative white when rendering image to screen) but its better to have actual coordinates (a proper CCSS applied on an accurate i1d3 or better device) when playing with LUT3Ds.

    DisplayCAL will do its best but physics laws can’t be broken

    Actually the source of that issue will have an statistical/genetic origin (+ damage by age).  Std observer is a mean/median whatever you name it and it will have some std dev, the closer you are to that, less likely this issues will happen.

    #36231

    Vincent
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    I forgot another source of error not related at all to metamerism => i1d3 firmware not accurate, sensivuity curves in firmware not matching actual device sensvivity curves. Related to cost & production statistics.

    So explained schematically:

    1-small to no observer metameric failure
    1.a- accurate i1d3 firmware
    1.a.i- small to no statistical deviation in SPD for a display model  => USE CCSS shared by somebody for that LED technology
    1.a.ii otherwise  => get an spectrophotometer and create a CUSTOM matrix CCMX correction valid ONLY for YOUR display & colorimeter
    1.b otherwise  => get an spectrophotometer and create a CUSTOM matrix CCMX correction valid ONLY for YOUR display & colorimeter
    2-mild observer metameric failure for your using certain LED technology (SPD) => visual white point editor, it’s the only solution here.
    3-otherwise return display and buy other with less narrow spikes SPD, or closer to the SPD presnet in the ones you have. Errors won’t be limited to mild color cast in white point.

    • This reply was modified 2 weeks, 3 days ago by Vincent.
    • This reply was modified 2 weeks, 3 days ago by Vincent.
    #36234

    ns1208
    Participant
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    I forgot another source of error not related at all to metamerism => i1d3 firmware not accurate, sensivuity curves in firmware not matching actual device sensvivity curves. Related to cost & production statistics.

    So explained schematically:

    1-small to no observer metameric failure
    1.a- accurate i1d3 firmware
    1.a.i- small to no statistical deviation in SPD for a display model  => USE CCSS shared by somebody for that LED technology

    My firmware is v1.03, found in the log file, in that case this is the accurate one right? No need to make any other changes?

    #36235

    Vincent
    Participant
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    I forgot another source of error not related at all to metamerism => i1d3 firmware not accurate, sensivuity curves in firmware not matching actual device sensvivity curves. Related to cost & production statistics.

    So explained schematically:

    1-small to no observer metameric failure
    1.a- accurate i1d3 firmware
    1.a.i- small to no statistical deviation in SPD for a display model  => USE CCSS shared by somebody for that LED technology

    My firmware is v1.03, found in the log file, in that case this is the accurate one right? No need to make any other changes?

    This is not related at all with firmware version.

    #36240

    Raj S
    Participant
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    Your solution is to perceptually match. Use a laptop with a WLED backlight, standard colour gamut (= only covers SRGB) display. Use DisplayCAL to calibrate it to D65 as normal. Then you can go onto your target monitor and try to match the whitepoint. Vincent already posted some instructions.

    About the firmware thing: Basically i1D3’s use filters to simulate how our eyes see. The accuracy can vary though. So X-Rite corrects this in the factory by creating spectral sensitivity curves for each device and programming it into the firmware. Their tolerance is 0.5-0.8 dE per device which means the accuracy of each i1D3 can vary. Usually it’s not too significant. You can always correct for this by profiling your meter with a spectro (or paying a calibrator to do it for cheap) but it’s not necessary.

    #36247

    Antonio Marcheselli
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    play white and tweak it manually until both monitors match. When they match, you can take a reading of your “new white” and then calibrate with that.

    ehm 🙂

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