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

[Peto Pedro]

Yeh it is guy above. 

I have q85t and am happy 

[kaveh serousheh]

Hi guys, i´ve done some testing with both my TVs (Q800T and Q7FN) and finally managed to fix the issue after 5 months!! you can test this if it helps for you guys aswell but be very careful like they say in hidden menu. 

I think this "issue" is somehow related to the hdmi 2.1 EDID and your console (Xbox Series S in my case)

When Xbox connected to my Q7FN this problem do not occur, it doesnt tonemap at all and the screen do not dims whatsoever.

When Xbox connected to Q800t hdmi 2.1, the TV tonemapping and dims the screen after few minutes.

I´ve got into hidden menu on my Q7fn (Hdmi 2.0b) and changed the EDID Hdmi from 1.4(??) - 2.1u. The TV started tonemapping in HDR calibration on xbox. the TV showed exactly 1000nits correctly before that. 

So the "problem" is either in the Hdmi version setting OR setting the correct nits/luminance etc in Xbox calibration.

SOLUTION:

On my Q800T:

1. I kept the orginal EDID Hdmi version 2.1 TM something.

2. i calibrated the contrast/black levels/brightness with Spears and Muncil CD.

3. i went into Xbox calibration settings and followed EXACTLY what the xbox says. 

4. i started a game (Forza 5) and played few minutes and then went back into hdr calibration directly via xbox button- HDR calibration shortcut.

5. Lowered the values again if i didnt see the squares or increased the values, then went back into the game again. i kept repeating this step until i saw no changes or absolute minimal changes in HDR calibration.

[peterQ95T]

Yes it was me that bought a Sony TV. I had the same issue with my Q95T as all other in this thread. I mean if you buy a "premium" TV you shouldn't have so many different issues with it.

 btw Samsung also replaced my TV  two times for very bad dse and dead pixels.

[Ulysses31]

2200 firmware on Samsung site. Seems to improve things for my Q950TS, when I play an HDR movie in windows there isn't an immediate drop in brightness when I go fullscreen that I have to bring back with switching between dimming levels. 

[kaveh serousheh]

Samsung Q800T 2020.  2200 Firmware seems to improved aswell issues related to HDR gaming for me. Someone knows if they implemented SBTM? 

[SaMoNe1986]

with the QE55Q95TATXTK  ,  the 6 min high local auto dimming bug is not fixed in PC MODE with the 2200.9 firmware update .

[kaveh serousheh]

Try turn off Pc mode dimming in samsung hidden menu, but keep in mind that all your previous calibrating settings will put in default afterwards and do it at your own risk. i ha e changed that on my Tv Q800T 2020 and i didnt get any issues. you can find this option under Option-Other settings- pc mode dimming (i think?).

To enter hidden menu try these buttons following: Info-Menu-mute - On/off. you should then see the Qled logo displaying and wait for about 20 sek.

[Ulysses31]

Playing a lot of Elden Ring in 4K HDR (game mode) on PC which forces 60 Hz in Fullscreen and I didn't notice any sudden drop in brightness in over 100hrs of playthrough.

Seems to be an issue with 120Hz.

[RouDeR]

It should not force 60hz,  if you have HDMI 2.1 GPU and TV you can play 4k@120hz HDR RGB at 10bits

[Ulysses31]

PC games can force 60 Hz in fullscreen, it has nothing to do with HDMI 2.1. The game is capped at 60 fps so even at 120 Hz in borderless window it wouldn't change much and with this local dimming bug you'd likely get the brightness loss in 120 Hz.

I saw there are mods to uncap the fps but that will likely get you banned online.