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

[cod]

I'm on 1302.4

[jayh89]

It doesn't come up on my TV. Did you use the USB method?

[cod]

Yeah, had to, TV wouldn't find it on the automatic update setting

[jayh89]

I spoke to chat, they weren't very helpful but gave me this email - uk.technical@samsung.com. If we could all email it and push for a fix? Maybe 1302.4 has the fix seeing as @cod has it? I don't have a USB pen to try! I can try buying one though.

[jayh89]

Although I found a change log for 1302.4 and it is this (no mention of fixing this) - 

Update version 1302.4 - July 2020
108 MP photos from the Galaxy S20 are now supported
Q-Symphony improvements

[Iskandarkebab]

Lately It is happening to me in a more random way, not always after 6 minutes but even after half an hour.

I also noticed that at least, with tlou2, brightness goes up again when the lighting changes substancially, as for example when changing from scenario or from scene to another with different lighting (like different time of the day)...so maybe the issue is related with brightness algorithm or something like that 

[Suriya]

Did you try the new update? 

[LCDeez]

I have the newest US update, not fixed. 

[KindOldRaven]

I've finally taken the time to really test for this issue on my Q90T and can confirm I also have this very same issue on the latest firmware. 

The reason I never noticed before is I currently don't watch or play a lot of HDR content and my SDR brightness is usually below '30'. When this 'bug' occurs, it basically dims down your brightness to about somewhere between 20-30 if you set it to the full 50. If you start below thirty when it occurs the effect isn't as drastic, which is why I didn't notice it at first. In HDR or with SDR high brightness settings it's very obvious though. 

Really there's a few weird things going on though. Standard local dimming will dim/brighten the frame for like 0.5 seconds whenever subtitles appear/disappear. Low and High don't have this behavior. The brightness bug might also happen more/less often depending on which local dimming setting you use, but that's just a thought - might have nothing to do with it.

[8bit]

I just want to chime in with my experience regarding this issue.

For me it only happens randomly when I'm playing my Nintendo Switch. Game mode on, local dimming high, hdmi input signal plus. I can never tell when it goes back up in brightness but it's very obvious when it lowers. 

For all of my other inputs (onboard streaming apps, PC) it never happens and for that I'm grateful, sounds like I could have it a lot worse. Strange though that it affects everyone differently. Really hoping for a fix in the next firmware update!