2020 QLED T models (Q80T, Q90T, Q800T, Q900T) HDR game mode brightness / local dimming bug

[Rauttis]

I bought a Q80T a couple of days ago and have noticed a really annoying issue when using the tv with the combination of HDR and game mode.

I'm fairly certain this is a software bug in the TV since I can reproduce this issue with 100% accuracy, and it happens on the dot at the same moment every time. It's basically on a timer.

Basically when the game is displaying a HDR signal and game mode is enabled, exactly after 6 minutes the brightness of the TV suddenly drops by around 20 (50 -> 30). The value of brightness setting doesn't actually change however. Messing with the brightness setting does not restore the brightness to it's original state, but changing the local dimming setting from standard to low and then back to standard does. Switching game mode off and then back on also fixes the issue, but then it happens again EXACTLY after 6 minutes (I've timed this with a stopwatch).

Has anyone else experienced this issue? Or can someone maybe test this on their TV to see if you can reproduce it?

Exact repro steps on how I can reproduce this 100% of the time on the PS4 Pro:

1. Set brightness to max (50)
2. Set local dimming to standard (bug happens on high as well)
3. Enable game mode
4. Turn off game motion plus
5. Turn off intelligent mode and all the brightness related settings in eco settings, as these can influence the brightness level of the tv.
6. Launch a game that runs in HDR
7. Start your stopwatch
8. Do whatever you want in the game or you can also go back to PS4 menus, find a bright scene where you can notice a brightness drop easily
9. When the stopwatch hits 6 minutes, you should see the TVs brightness suddenly drop by a large amount. By eye the brightness drop seems about equal to dropping the brightness from 50 -> 30 by hand.
10. Go to picture settings and set local dimming to low (brightness does not change)
11. Set local dimming back to standard (brightness suddenly jumps to the original level. Brightness can be restored by switching input away and back as well, or by disabling and re-enabling game mode)
12. And again after EXACTLY 6 minutes the bug again repeats and the brightness drops down again

Some other notes: The PS4 has a screensaver that basically dims the screen if it is idle for a while. This is not the cause of this, this happens even when the console is in active use and the brightness can be restored temporarily by changing the local dimming setting like described above. I have not managed to reproduce this issue with game mode off, so it seems to be related to game mode.

Software version: 1304

[Suriya]

Already i did

https://eu.community.samsung.com/t5/tv/q95t-game-mode-green-purple-blue-tint/m-p/1966113#M47234

[Keitoki]

Same for me... it's a shame, i can't play on this tv, pc mode is full of artefacts/ghosting, patch this ***** samsug please...

[LCDeez]

Let’s try to keep the ghosting issue out of this thread if possible. Since another thread was made, post there. It can really muddy the waters if we’re discussing too much when the entire point of this is the dimming bug. 

[SidL]

And maintain the claim that local dimming does not work if GMP is disabled

[Rkss]

Isn't this bug on last year model as well?

I've seen similar complaint about Q80R Q90R's local dimming on game mode

[Suriya]

GMP off local dimming is not effective but it is working. GMP on local dimming is little better. I prefer GMP off looks brighter and colorful 

[LCDeez]

GMP off has the lowest input lag. 

[Danboy76]

Ok, about 20 pages back I said that I had a Q80T (the model number is QE55Q80TATXXC) and I said that I had not yet experienced the bug whilst in game mode on my xbox one x. I have GMP deactivated, and have really looked for it in both HDR and SDR and thankfully have been really lucky. I always watch netflix through my xbox (even though I have my account set-up for the tv) and watch everything exclusively through HDMI.

Well tonight my kids were watching netflix through the app on the tv, and to my horror it started dimming. Once dimmed, nothing would sort it out. Only switching the tv off or strangely changing to my xbox and then going back to the app. But that was only a temporary fix because it would start dimming again. Changing to the youtube app or switching to normal tv would do nothing, and the unchangeable dimming would remain...

When I got my tv, I only really messed around with the settings on HDMI, with one of the first things that I did was change the eco settings to off, but before I did that, I set the minimum brightness to max (50), before switching off all eco settings.

When I was checking my menus earlier before calling the shop in the morning, I went into the eco settings and saw the following. Everything was off, just that the minimum brightness was set to 18. I switched on the eco settings, then put the minimum brightness to max and switched them all off again.

Lo and behold the screen immediately brightened, and I left it on for an hour and it didn't dim once.

I don't know if that is a coincidence or not. I did say about 20 pages back that it might be a long shot, but to check your minimum brightness settings in the eco menu because I had never seen the dimming on my set and I had adjusted my minimum brightness day one. Again, I don't know if that is the fix or a band aid or if the bug does really come from that setting. But for me that resolved my problem earlier, and like I said, I have never had the problem on my xbox in game mode in SDR or HDR. 

[RouDeR]

It is coincidence, this is one of the first things that I`ve tried, however dimming bug still occurs from time to time.

[Suriya]

Already tried these few weeks back no use. First off vrr and see playing games with game motion OFF