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Wayland Color Management Protocol Posted For Weston

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  • Originally posted by Quackdoc View Post
    it's important to remember, that the amount of luminance levels that you can actually visibly see, changes when you apply a better transfer.
    Its important to remember that if you dont evenly space the quatisation levels, the dynamic range decreases because the minimum value you can measure/emit increases
    e.g. lets say instead of 1 nit for the lowest value of 255:1 you use 0.3 nits
    all of your other spacings now have to increase to 1.0028 nits per level and your dynamic range is now 255:1.0028 < 255:1


    Just like perpetual motion, it doesn't matter how you try and fake it, you can't put more information into 8 bits than 255 levels, dynamic range and bits measure the same properties of information, but ones analogue, the other is digital.

    That, btw, is exactly how you downscale the "real world" with generally a 1,000,000:1 dynamic range, to an SDR image with a 255:1 dynamic range, and why darks/lights end up "washed out" depending on which end of the scale you clip on.
    Last edited by mSparks; 06 October 2023, 11:28 AM.


    • Originally posted by Quackdoc View Post
      HDR10 and dolby PQ are both color spaces, HDR400/600 etc, get very close to being colorspaces, as HDR400 defines srgb support, 8bit color, brightness, and at least a PQ transfer curve,
      This means you are now over-bright. PQ P3 is over bright srgb/ Rec. 709

      Originally posted by Quackdoc View Post
      don't assume that REC2020 is the only HDR spec
      To be correct is not assume by me. REC2020 for SDR parts of the specification references REC709. I did check what REC2020 says SDR should be.

      DCI-P3 65 is the wrong color space. The define points being the 3 corners and the white point of srgb and Rec 709 absolutely align with each other there is only a nits difference. DCI-P3 65 white point lines up but the 3 corners don't line up with REC709/srgb at all.

      HDR10 is not a color space it s certification.

      HDR10 color space is ITU-R BT.2020 that can also be written as REC2020. With certification/calibration performed SMPTE ST 2084 standard but that different to what REC2020 says should be used. Now we have a problem SMPTE ST 2084 allows for a larger margin of error than REC2020 certification/calibration method says is acceptable.

      HDR400/600 are not certified to output srgb correctly. They are certified to output srgb as per PQ P3 that is srgb/reg709 rendered washed out because the 3 points have been moved in the color space.

      If you are not use to seeing srgb rendered correctly you would think that PQ P3 is correct when it not comes very important when doing color matching and other things.

      Basically HDR400 HDR600 if you test against pure REC2020 they are all wrong.

      This leads us to a bigger problem. Movie industry like this incorrect form of REC2020 that uses SMPTE ST 2084. This means you cannot watch movies that are right and have srgb/Rec709 that is right at the same time. Srgb/Rec709 being washed out on monitor in HDR mode is in fact rendering correctly as per monitor certification in most cases.

      Yes people complain that their movie rendered too dark in places on pure REC2020 certified monitor is also correct. Yes pure REC2020 is darker colors than the REC2020/SMPTE ST 2084 hi-bred in the center area due to how the bits align in the color space.

      This is a calibration and color space problem. Yes Quackdoc if you are using HDR400 monitor and you are claiming srgb/REC709 is rendering correctly while HDR content is displayed like it or not you are talking out your ass those monitors are not in fact able todo that. You need to break out a color meter and correctly check you will find the srgb is values incorrect all in the direction of being too bright/washed out.

      Problem is the DCI-P3 65 is not srgb/REC709. Now if you were claiming HDR400 monitor can do DCI-P3 65 content correctly you would be correct but do remember that is over bright and looks washed out to those who are use to looking at properly calibrated srgb/REC709 monitors because DCI-P3 65 is the wrong color space.

      This is why we are checkmated. We need to accept for most HDR monitors we will not be able to display srgb/rec709 correctly while displaying HDR content because the monitor is incapable of doing it. If you have HDR monitor capable of displaying srgb/REC709 correctly while displaying HDR content the HDR content is going to be not displayed as intended in lots of cases. This is a true rock and hard place.