Originally Posted by Javs
Im getting a colour shift using MadVR's tone mapping too. This time for me I notice it in the reds.
Originally Posted by Javs
Thanks, thats good to know the Oppo does seem to be outputting the right colour then.
And also good to know there does seem to be an issue at least with my MadVR setup, I am sure its something that will be worked out eventually. Those white blotches, those are something I do take issue with, and why I don't use the MadVR tone mapping right now. The colour shift is also annoying, but yeah, it is what it is.
Some things to think about
1) The only way to truely know how the HDR Blu-Ray is supposed to look like is to play it on a true 10,000 Nits BT.2020 display. (Ok, a 4,000 Nits DCI-P3 display would also do, if the combination of player and display are clever enough to *clip* both luminance and colors, because tone mapping is in this case not necessary, because the movie's actual data fits into 4,000 Nits DCI-P3.)
2) Let's say you have a highly saturated red color which the HDR Blu-Ray has encoded with 4,000 Nits. And your display actually *can* do 4,000 Nits. No problems, right? Actually yes, BIG problem, because the display peak Nits capability is for white, not for red. So what should a tone mapping algorithm do now? Should it make the pixel white? It could achieve the wanted 4,000 Nits, but the pixel's color/saturation would be completely lost. Or should the tone mapping maintain the full saturation/color, and lose all the Nits it can't handle? Then a significant amout of highlight punch & detail would get lost. So what should we do? In madVR you can choose. See option "fix too bright & saturated pixels by".
3) Let's say the studio uses a sub-optimal tone mapping algorithm for their 1080p Blu-Ray. Or maybe they use a custom tone mapping algorithm to achieve a specific look, or maybe (for high profile titles) they're even tuning it for each different scene. How then can you use an 1080p Blu-Ray as a reference for a tone-mapped HDR Blu-Ray should look like?
4) Every CE manufacturer has their own tone mapping algorithm, and they all look different. So who's right and who's wrong? Who can be accepted as reference? And all the others are then judged to have color shifts?
All that said, if you're not completely happy with madVR's tone mapping results, here are a few things you could try:
A) Try different values for the "fix too bright & saturated pixels by" option. See point 2) above. There's no right or wrong setting here, unfortunately. In some scenes one setting looks better, in other scenes another.
B) You could try to turn "preserve hue" on/off in madVR, or switch between "low" and "high" quality. FWIW, "high" quality is doing the tone mapping in ICtCp, which is Dolby's preferred color space for tone mapping.
C) You can use DisplayCAL to create 3DLUTs which include HDR -> SDR conversion (tone mapping). The 3DLUTs are calculated offline, by also using the ArgyllCMS framework, IIRC, so it should be very high quality. Maybe you prefer it over what madVR's pixel shader math does? Here's a test 3DLUT you can try, which doesn't do any actual display calibration, but just does tone mapping, nothing else. Tone mapping is done to 400 Nits and BT.709 gamut by this test 3DLUT:
You can enter this in the BT.2020 slot when switching madVR to "convert HDR content to SDR by using an external 3DLUT". Of course you can create any tone mapping 3DLUT you want (different nits values and gamuts) with DisplayCAL.