Gamma flikcering issues when PC gaming on a LG CX 65 inch

jackol4ntrn

Novice Member
Hi all,


I have some serious gamma flickering issues when playing PC games, especially when HDR enabled.


The settings on the TV are: instant game response on, AMD freesync on, HDR game user picture setting, firmware fully updated to latest
The settings on the Computer is: 4k RGB Full, 120 Hz, Gsync enabled full screen only (RTX 3080, fully updated)
Connect via HDMI 2.1 cable


The games I play include: RDR2 and Horizon, both are running in half of the 4k resolution, for decent frame rates (anywhere from 60 to 80 fps)


Constant flickering, very noticeable in dark areas. I know this has been addressed before, but people are saying it was "fixed" with recent updates. I don't see it. If I turn off Instant Game Response, the issue goes away completely, but then VRR is disabled. Is there something I'm missing or do I have to just deal with the flickering or not use one of the biggest selling points, VRR?
 

next010

Distinguished Member
Hi all,


I have some serious gamma flickering issues when playing PC games, especially when HDR enabled.


The settings on the TV are: instant game response on, AMD freesync on, HDR game user picture setting, firmware fully updated to latest
The settings on the Computer is: 4k RGB Full, 120 Hz, Gsync enabled full screen only (RTX 3080, fully updated)
Connect via HDMI 2.1 cable


The games I play include: RDR2 and Horizon, both are running in half of the 4k resolution, for decent frame rates (anywhere from 60 to 80 fps)


Constant flickering, very noticeable in dark areas. I know this has been addressed before, but people are saying it was "fixed" with recent updates. I don't see it. If I turn off Instant Game Response, the issue goes away completely, but then VRR is disabled. Is there something I'm missing or do I have to just deal with the flickering or not use one of the biggest selling points, VRR?

So the problem here is that the TV's gamma curve is optimized for fixed 120hz output and its not dynamic.

So as VRR keeps games smooth by dynamically matching the FPS to the refresh rate, the further away your FPS is from 120 the more the chances increase of the gamma shift being noticeable. This issue has largely been masked on PC monitor LCD's due to their terrible contrast performance but on OLED its much more visible.

This can only be properly fixed by new hardware in the display, but via firmware update what LG has done is provide a compensation tool called "Fine Tune Dark Areas" which manually adjusts the gamma curve in VRR. However as this is not dynamic it can affect games differently.

The general recommendation is to set to -3 as a compromise option if you don't want to alter it for every game.

AMD Freesync should be off, the RTX-3080 uses HDMI-VRR (branded as G-Sync compatible), the IGR is what toggles HDMI-VRR on/off.

The CX has a VRR range of 40-120Hz, below 40 LFC will kick in doing frame doubling so 30x2 is treated as 60fps to be smoothed by VRR this can be part of flickering source too. Sadly there is no way to disable LFC other than run at 60hz were it cannot frame double.

The other option is disable g-sync and turn vsync off in all games, this will solve the problem at the expense of screen tearing though that depends on the game and may not be noticeable at all in some.
 
Last edited:

jackol4ntrn

Novice Member
Gotcha, thanks for that.

So in the end, after more tests, I've decided to run the games in 60Hz capped instead of 120. This eliminates the gamma flickering since the Hz and frames aren't jumping around and are constant 60fps, sometimes dipping to mid 50s for a second or two.

I've decided that since I'm playing somewhat cinematic games like RDR2 on the TV and not competitive games like Counter Strike or whatever, I don't need the extra 30 fps to play it when I can just deal with 60Hz in 4k and no longer see the gamma flickering, especially in dark games.

It sucks that this flickering exists and I would need something akin to a 3090 TI or whatever to get 120 frames if I ever wanted to play in Ultra settings, but I don't need 120Hz as I have a 144hz g sync PC monitor for competitor gaming.
 

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