HDR Caibration

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  • #13544

    Marcelo Cosme Carlos dos Santos
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    Hello, I use DisplayCAL to calibrate my reference monitor through Davinci Resolve (SpectralCal CalMAN). Currently I have acquired a 4k UHD monitor that recognizes 100% REC 709, 97.7% DCI-P3, 76.9% REC2020 … What is the best way to do the calibration? Do I use the standard Resolve Rec709 D65 or should I try to change to HDR D65 Rec 2020?

    #13555

    Florian Höch
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    Hi,

    my recommendation would be to profile the display in its largest gamut mode (i.e. native), but preferably in SDR mode (but with high brightness), not HDR, as the display’s own tone mapping may interfere with profiling (unless there is a way to switch said tone mapping off). Then, use the Resolve Rec. 709 preset as a base in DisplayCAL, but change input color space on the 3D LUT tab to Rec. 2020, and tone curve to SMPTE 2084 (hard clip) and change target peak to the value you want to use (usually >= 1000 for HDR10). Make sure to not exceed that range when grading. Depending on your actual display target peak capability, the image may be darker than it would be on a display which can reach the chosen target peak.
    You can also create an additional LUT with DisplayCAL tone mapping enabled by setting 3D LUT tone curve to SMPTE 2084 (roll-off), which will allow you to preview how your grade might look like on a display with high quality tone and gamut mapping.

    #13560

    Marcelo Cosme Carlos dos Santos
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    Hi Florian, thanks for the reply. But sorry for my lack of understanding. My monitor is a Dell UP2718q … A consumer model. In your answer you made me choose the native range, this you say in the correct monitor? For example leaving it in factory mode … And in the displayCal I use the standard setup of the Resolve 709 D65 and change the properties of the kit for 2020 and 2084 roll off … Correct?

    #13564

    Florian Höch
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    Yes, although for grading, don’t use roll-off (tone mapping), use hard clip.

    #13592

    Willian Aleman
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    Yes, although for grading, don’t use roll-off (tone mapping), use hard clip.

    This is an interesting recommendation. I thought that roll-off offers a better gradation between ranges than hard-clip. Is this a particular recommendation for the way DisplayCAL implement the tone mapping or is it to be applied in general to HDR?

    #13601

    Florian Höch
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    This is an interesting recommendation. I thought that roll-off offers a better gradation between ranges than hard-clip. Is this a particular recommendation for the way DisplayCAL implement the tone mapping or is it to be applied in general to HDR?

    My recommendation is specific for grading, not (end-user) playback, based on how high-end HDR grading monitors like the Sony BVMs seem to operate (i.e. no tone mapping). HDR grading is still a relatively new thing, best practices are going to evolve over time.

    #13646

    Willian Aleman
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    Hi,

    my recommendation would be to profile the display in its largest gamut mode (i.e. native), but preferably in SDR mode (but with high brightness), not HDR, as the display’s own tone mapping may interfere with profiling (unless there is a way to switch said tone mapping off).

    Accordingly, with the new SpectralCal, LG 2018 OLED and SUHD Reference Guide, manual dynamic tone mapping is optional disable, including, dynamic contrast, dynamic color, preferred color, among other parameters.

    The only remaining issue to be solved is how to avoid the LG C8 display to dim during calibration, which SpectralCal auto calibration does.

    #13649

    Florian Höch
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    manual dynamic tone mapping is optional disable, including, dynamic contrast, dynamic color, preferred color, among other parameters.

    That is certainly good for calibration.

    The only remaining issue to be solved is how to avoid the LG C8 display to dim during calibration, which SpectralCal auto calibration does.

    How do they do it? Black frame insertion? Or via a proprietary API?

    #13651

    Willian Aleman
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    Here is a quote from SpectralCAL LG user guide in reference to the implementation:

    “Full Field Pattern Insertion (OLED ONLY)

    To prevent an LG OLED display from entering its auto dimming mode during extended measurements, the CalMAN Pattern Insertion feature periodically inserts a different test pattern during extended test pattern measurements, to reset the display’s auto dimming timer.

    Under CalMAN Settings > Application Measurement Options, set the following Full Field Pattern Insertion options:

    • Frequency: 5 (seconds) • Duration: 5 (seconds) • Level: 15%”

    #14021

    Florian Höch
    Administrator
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    Full field pattern insertion is now available with DisplayCAL 3.7 when using madTPG, Resolve or Prisma pattern generators.

    #23420

    Marcelo Cosme Carlos dos Santos
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    FLoria, in 3D tab…
    Should I leave Full Range encoding at 0-255 or change input and output to TV Rec.2020?

    #23736

    Florian Höch
    Administrator
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    Leave at 0-255, the YCBCr encodings are for very specific situations that typically don’t apply unless you use specific equipment.

    #23857

    Wire
    Participant
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    Marcello,

    To be clear, when you say factory mode, per Florian “native”, Dell’s most native mode is Custom Color with default subsettings. Precal white by backing Gains off from 100 as minimally as possible.

    Standard mode is most Native with Dell’s idea of D65. But you can do significantly better by playing with Custom Color to pre cal white.

    Dells gain controls are a bit coarse and Offset can refine if used with care.

    If you really want to get white, use command line and spotread -T -y 1 to measure. Adjust gains to get close as you can to 6500 / 0.5 dE Visual Temp, then refine with +/– 1  step of R,G or B Offset to perfect white. Use R and B controls to get temp closest to 6500 and G to home in on dE < 0.5 (no more that 2 Offset delta to avoid reducing contrast and peak luminance) then let DisplayCal handle grays.

    You want the minimal control adjustments to get to the target white

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