Question LG 34GK950F-B Orange on Text tint at 144Hz

Apollox

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Feb 24, 2008
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Just got my first 144Hz monitor, LG 34GK950F-B, and having a bit of a problem. At 120Hz, works just fine. At 144Hz, though, things get a bit ugly. Text is blurry, and appears to have a slight glow around letters. Certain combinations of letters are immediately noticeable. Like if I write the word "monitor" 20 times in a row in a text editor, the "i" in the middle appears orange compared to the rest of the letters on every line, no matter where on the screen I drag it.

I've tried adjusting the monitor settings and confirmed nothing special is enabled (no 1 ms response time for example). In fact, it appears to discolor text no matter which mode it is.

Other oddities - Even at lower resolutions 1920x1200 (versus native 3440x1440), the problem is noticeable at 144Hz. Also, anytime I change resolution or displays, Windows always pushed me back to 120Hz.

Suggestions? Is this a bad monitor? Bad cable (I'm using the 5k one that came with it)? I'm also using a 980TI (with the firmware fix for DP 1.4), but since this is happening at lower resolutions, I don't think this is the culprit.

Any ideas? See picture below. When I switch to 120Hz, the iiii is black, but at 144Hz, the iiii is orange-ish.



One last comment... if I drag the text screen around slowly.. I see the orange flip to blue and back to orange. And I'm only moving it a hair.
 
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Apollox

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One other oddity, if I turn off Windows ClearType the problem goes away. It seems like I have to choose between 144Hz and ClearType... any ideas?
 
Mar 10, 2019
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Hey, I just got this monitor as well and wanted to offer you some kind of solution to your issue.

This seems to be an issue for me when the color output of the monitor is set to YCbCr422 within the Nvidia Control Panel.



Once I changed this to either be RGB or YCbCr444 the orange font issue went away. Hope this helps.
 

Apollox

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What graphics card do you have? At 144Hz, I only have color depth of "8 bpc", format of "YCbCr422", and range of "Limited". The other options are only available if I lower the refresh rate.

At 100Hz, RGP/YCbCr422/YcbCr444 and 8/10 bpc are available.
At 120Hz, RGP/YCbCr422/YcbCr444 and 8 bpc are available.
At 144Hz, only 8 bpc, and YCbCr422 are available

Is this a graphics card limitation or something else I'm missing?
 

Apollox

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On the plus side, you did confirm the output color format is the problem. If I go to 60Hz with YCBCr422, the same discoloration I saw at 144Hz appears.
 

Apollox

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Figured it out. It’s a limitation of the 980ti. I borrowed an RTX 2080 and the problems went away. I was able to display RGB, YCbCr422, and YCbCr444 at full/limited 8/10 bpc without any distortions.

NVidia released a firmware update so older cards could support DP 1.4 but I’m guessing 144Hz 3440x1440 pushes the card slightly past its limits. It can do 120Hz well, but starts to fall apart at 144Hz, hence the orange tint. Wonder if 1080 has similar problems.
 
Apr 23, 2019
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I'm running into the same probleem with a GTX 1080. Upper limit is 120 Hz.
Waiting for AMD Navi, spend al my money on the LG 34GK950F ;-)
 
Mar 10, 2019
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I just had this problem come back the other day and strangely enough, I was able to get it to go past 120hz just by unplugging and replugging the display port cable from the back of my monitor. Hopefully, if anyone else stumbles upon this thread they are at least able to narrow it down to the output color format setting.
 
Reactions: FreakyMax
Apr 23, 2019
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I just had this problem come back the other day and strangely enough, I was able to get it to go past 120hz just by unplugging and replugging the display port cable from the back of my monitor. Hopefully, if anyone else stumbles upon this thread they are at least able to narrow it down to the output color format setting.
Thank you! That also solved the problem for me!
I think that I figured out what initiated the problem in my case.
I have two HP monitors (portrait mode left and right from the LG) that I plugged in after connecting the LG.
If I plug in the HP monitors after the LG the display properties return to only 8 bpc and YCbCr422 being available. Something in Windows can't handle this sequence.
If I plug in the HP monitors before the LG monitor, no problem.

Back to glorious 144 Hz in full colour mode :)
 
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