Apple Thunderbolt Display calibration

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  • #26930

    BB2020
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    I am looking for the best calibration workflow for a Apple Thunderbolt Display (with Radeon Pro 560 4gb) as second monitor to a iMac. I do have a X-rite i1 Display Pro and the software which I am going to use is DaVinci Resolve 16. Since the Display is connected through Thunderbolt I am aware I need to work in my GUI viewer. So my plan is send out calibration patches from Resolve, do the calibration and profiling in DisplayCal which will be saved as a 3D LUT and used as “3D Color Viewer Lookup Table”  in Resolve.

    Is there some other things I need to bear in mind? Like i.e. what brightness should the display be set to for the best results? Is it wise to change gamma of the calibration and the timeline color space? The delivery is for web, and the rooms has a pretty light environment (but we can block some windows if needed).

    i1Display Pro on Amazon  
    Disclosure: As an Amazon Associate I earn from qualifying purchases.

    #26934

    Vincent
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    Apple Thunderbolt Display like an imac is like a big laptop screen with the same limitations. Youe are somehow locked to factory values but you can change brightness. Additionally macos color management on desktop is extremeñly limited & faulty, so unless you want to see some artifacts on apple’s apps including desktop UI, you’ll be forced to use simpler profiler for general use. You’ll get a warning screen if you want to do it other way, but you can ignore it.

    Since whitepoint is going to be corrected limiting some channel output (if you want to correct it), because they are just big laptop screens, final brightness after calibration may drop. Try to make an educated guess about how much it will drop. The further native whitepoint is for your target white point the more it will drop. If you do not know try first doing nothing, if brightness drops raise it or set as staring point +5-10% from your target value.

    Those are your particular limitations. As a general rule that you may have learnt reading other threads:
    -Imac/thundb displays with sRGB like colorspace => correct measurements with White LED colorimeter correction for i1displaypro, bundled in displaycal
    -Imac/thunderb displays with P3 colorspace => use WLED PFS forrection for macbooks with P3 screen. it’s bundled with display too.

    Then just follow DisplayCAL Resolve wiki.

    • This reply was modified 1 week, 6 days ago by Vincent.
    #26953

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    Hi Vincent, thank you for helping. Just to understand you clearly; what do you mean with final brightness may drop after calibration? I will turn off the “Automatically adjust brightness” option, set and leave the brightness (I think to 50%) and do the calibrate. I understand some channel can have a limited output by correcting it to the right whitepoint, but it should also be sticked to the chosen white level right?  Or is it recommend to leave the white level on “As measured”?

    #26956

    Vincent
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     what do you mean with final brightness may drop after calibration?

    Like in a laptop non limited GPU when you send 255 white to GPU it will send to display 255 reg, gren & blue and display’s response will have some color coordinates CIE XYZ, or simplified xy for color tint  + Y for cd/m2

    If you wish to modify native white because it is not the one you want, then after calibration you will end with something like 255 white -> 255 red, 250 green, 240 blue. It’s an example of a bluer than D65 native whitepoint.
    That means that when you want to show white, display ouput will be lower because it has been corrected in GPU, hence resulting cd/m2 are lower that starting value.
    The bigger the distance to target white (in green most) the bigger will be brightness drop.

    If you raise manually brightness on OS white point may  drift. You an plot it uncalibrated: xy white point coordinates as you move brightness slider. It depends on your actuyal display. So it is possible that you may to start with +5-10% of your target luminance when correcting whitepoint in GPU and do not modify brightness slider afterwards.

    On top of that you have specific apple limitations due to their faulty color management engine on desktop apps that use it.

    • This reply was modified 1 week, 4 days ago by Vincent.
    #26987

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    It makes sense, thanks for you explanation. So if my target will be 100 cd/m2, it is wise to calibrate (depending on your display) lets say on 110 cd/m2 which is hopefully getting you in the right ballpark so you don’t have to manually change brightness afterwards, or elsewise start over and find out which brightness give the closes results?

    #26988

    Vincent
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    Check if whitepoint drifts with brightness change. If it does not matter, you can use brightness slider afterwards.

    #26997

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    Good tip, thanks. I’m doing some testing now, but do I need to set the output encoding to TV RGB 16-235 for using in Resolve to have a match with the rec709 video levels?

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