Originally Posted by thoth
Keep local dimming at High for HDR Movie mode. On my 75", in HDR Standard picture mode, local dimming Standard measures about the same as local dimming High. But local dimming Standard has horrible peak brightness in HDR Movie mode. It might be tolerable for the Mandalorian, given that particular show's reported measly fake HDR, but not much else.
Thank you! I tried both, and with Standard Picture Mode and Standard Local Dimming it seems slightly better, but with Movie Picture Mode and High Local Dimming it seems much better. It's still there, but not so distracting like before.
I'm aware that The Mandalorian is "fake HDR" in that it's only 2x SDR, but even so this shouldn't excuse any fixed-frame illumination non-uniformity issues. So, I just tried playing these scenes on my old-ish LG B6 OLED to check if there's anything in the content that could be causing this. On the OLED, I noticed that on these scenes there is a mild sort of "reverse vignette" effect around the edge of the frame! This could completely explain the cloudy backlight blobs I was seeing, if this particular 'reverse vignette' effect happens to be interacting poorly with the local dimming algorithm. It could also explain why I haven't seen the issue anywhere else so far.
As long as it's subtle and content-specific, I'd be totally okay with particular reverse vignette effects interacting with some subtle imperfections in rare cases -- that comes with the territory of FALD (even the best, like this), and would probably be unrealistic for me to expect OLED dark-room dark-scene precision here. All other content so far looks great (though I need to find more dark scenes to test), and so far now with the Movie Mode it also looks good here so far (though it's bright enough outside now that I need to wait for night again to truly confirm dark room performance).
So long as I don't detect the same
pattern of blobs showing up in all content, this won't be bothersome to me and probably is just a regular (and rare) artifact from reverse vignette interacting with the FALD algorithm. Also, the letterbox bloom in of itself doesn't really bother me, and Movie Mode seems to have improved that as well.
However if I find the same exact pattern of cloudy blobs on other content, that will definitely be very annoying in the long run. Hopefully that doesn't happen though.