Corrections for wide gamut display with sRGB clamp

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  • #140501

    honman
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    I recently got an LG 32GQ950, which is the first wide gamut display I’ve owned. I’ve had much success with using displaycal to calibrate other displays, but none were wide gamut. My process for those involved first generating a spectral correction using my i1pro 2, comparing the result to the built in 1nm corrections and using one of those instead if it matches closely, then doing the full calibration/profiling procedure with my i1d3 and that correction. In the case of the LG, I’m trying to understand a few things, like how the hardware sRGB clamp function affects things:

    1. Do I need to create a correction for each mode individually, or can I use the wide gamut correction when the sRGB clamp is enabled as well?
    2. Is this the case when both doing the calibrations and verifying them?
    3. I know my i1pro 2 is not accurate enough to fully measure this type of display. From what I can tell based on the measurements, the backlight type is definitely some kind of PFS phosphor WLED. When compared to the built-in “LCD PFS Phosphor WLED Family” correction, the chromacity coordinates of my correction line up with 1 set of coordinates, but not the others. Will that affect the accuracy of my calibrations if I use the built-in correction rather than my own?
    4. Even if the built-in correction doesn’t match mine perfectly, would the higher 1nm precision by itself make it more accurate than the one generated by my i1pro 2 anyway?

    For reference, I attached my correction as well as a photo showing what I’m comparing it to.

    Thanks in advance for any replies!

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    #140504

    Vincent
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    I recently got an LG 32GQ950, which is the first wide gamut display I’ve owned. I’ve had much success with using displaycal to calibrate other displays, but none were wide gamut. My process for those involved first generating a spectral correction using my i1pro 2, comparing the result to the built in 1nm corrections and using one of those instead if it matches closely, then doing the full calibration/profiling procedure with my i1d3 and that correction. In the case of the LG, I’m trying to understand a few things, like how the hardware sRGB clamp function affects things:

    1. Do I need to create a correction for each mode individually, or can I use the wide gamut correction when the sRGB clamp is enabled as well?

    No, all modes are a mix of native RGB primaries. Use native gamut CCSS for all

    1. Is this the case when both doing the calibrations and verifying them?

    Yes, native CCSS for all.

    1. I know my i1pro 2 is not accurate enough to fully measure this type of display. From what I can tell based on the measurements, the backlight type is definitely some kind of PFS phosphor WLED. When compared to the built-in “LCD PFS Phosphor WLED Family” correction, the chromacity coordinates of my correction line up with 1 set of coordinates, but not the others. Will that affect the accuracy of my calibrations if I use the built-in correction rather than my own?

    Split PFS_family.ccss in  several ones, each model 4 rows, WRGB, the compare, or compare by channel and create an hybrid by yourself (find the closest green and the closest red, then compute W as=r+g+b, maybe with some scaling/normalization)…. but I’ll say that your 3nm correction will be good enough.

    1. Even if the built-in correction doesn’t match mine perfectly, would the higher 1nm precision by itself make it more accurate than the one generated by my i1pro 2 anyway?

    Does your LG display “look white” (no green – pink tint) once calibrated to D65 with your i1d3 + custom 3nm CCSS? If yes, that’s all. If no it could be caused by several reasons, ranging from your own visual system, to innacurate spectral sensivities stored in id3 firmware,  to innacurate correction.

    For reference, I attached my correction as well as a photo showing what I’m comparing it to.

    Thanks in advance for any replies!

    • This reply was modified 4 months, 3 weeks ago by Vincent.
    #140572

    honman
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    Hi Vincent, thank you for your reply.

    No, all modes are a mix of native RGB primaries. Use native gamut CCSS for all

    Makes sense. Out of curiosity, is there any scenario where having a separate sRGB CCSS is useful? When I look through the database I see quite a few user-submitted CCSS (and CCMX for that matter) of both sRGB and native gamut for many different wide gamut monitors. I’m guessing most of those are from people who weren’t sure if they needed them or not and just clicked OK on the “would you like to submit this to the database” popup.

    Split PFS_family.ccss in  several ones, each model 4 rows, WRGB, the compare, or compare by channel and create an hybrid by yourself (find the closest green and the closest red, then compute W as=r+g+b, maybe with some scaling/normalization)…. but I’ll say that your 3nm correction will be good enough.

    Interesting; I may try that at some point. For now I’ll stick with my 3nm correction.

    Does your LG display “look white” (no green – pink tint) once calibrated to D65 with your i1d3 + custom 3nm CCSS? If yes, that’s all. If no it could be caused by several reasons, ranging from your own visual system, to innacurate spectral sensivities stored in id3 firmware,  to innacurate correction.

    It does as best I can tell. I was running into an issue when I was trying to do hardware calibration, which unfortunately only works with LG’s far inferior calibration studio software. Every attempt resulted in a bad red/pink tint. I eventually realized that it was applying a standard WLED correction (because LG’s software devs apparently don’t know the panel types of their own hardware) and figured out I could force it to use my correction by converting it to EDR and replacing the incorrect EDR with mine. Now the hardware cal is MUCH better, but still needs displaycal’s calibration on top of it to be ideal.

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