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Acer XB241H scanlines at 144hz and up

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Acer XB241H scanlines at 144hz and up

Postby Pride » 07 Oct 2018, 15:39

Hi all,

New to the forums, and the topic title is pretty much the reason I found these forums in the first place, thanks to some Googling on the matter.

I bought this monitor about a week ago, and pretty much on day 1, I noticed the monitor had some visible 'scanlines', mostly at the bottom left section of the screen, but only at 144hz and up (veeeery minor at 120hz). Extremely visible when overclocked to 180hz (even from far away). Thanks to a lot of peeps on this forum, I realized it's a "panel lottery" thing, and that it's quite common for 24" 144hz monitors to have this issue.

I have a few questions, though. Can something be done about it? Would installing drivers for the monitor have any effect? What about Nvidia drivers? Would it help to change DisplayPort cable (the one I'm using now came with the monitor)? Are there settings in Windows/NVIDIA I can change that might help? How much of a lottery is there? If I exchange the monitor, what are the changes my new one will also have these scanlines? 100%? 50%? 1%?

I'm very much doubting whether I should RMA the monitor because of this, and I'm wondering if I should buy a better DisplayPort cable (the one that's highly recommended is 30 euros). I bought this monitor primarily for the 144hz, so it's a real pity if nothing can be done.

Thanks in advance!
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Joined: 07 Oct 2018, 15:26

Re: Acer XB241H scanlines at 144hz and up

Postby Chief Blur Buster » 07 Oct 2018, 22:10

This type of scanlines artifact is unfixable on many TN panels, it's often a panel issue.

Cable won't help. It's physical.

Voltage nonuniformities of LCD pixel driving grid is amplified when there's less time to refresh pixels (e.g. 180Hz vs 120Hz), and this is very common when a panel is driven well beyond its own specifications. The scanlines artifact affects TN panels far more than other panel tech.

If you need high Hz without scanlines, get a 240Hz panel. I have not seen scanlines on any of my native-240Hz panels.

I've seen this years ago too, on LightBoost monitors (upper-right corner of VG248QE in LightBoost mode). Scanlines also happen in LightBoost modes on some panels, since during strobe mode, some panels run in essentially overclocked scanout (~1/150sec to ~1/180sec scanout at 120Hz to create longer blanking intervals to let LCD pixel transitions finish in total darkness, before flashing the strobe backlight of a blur reduction mode such as ULMB/LightBoost/DyAc/ELMB/etc of any modern gaming monitor with a blur-reducing strobe backlight feature).

You can try reduced vertical totals to slow down the panel scan as much as possible, but there's a point where it doesn't help.

You can also try warmer room temps and see if it helps a bit (Colder room temps tend to amplify this artifact more). We've forgotten our smartphones in a car in the winter, and the screen all behaves weird? Same thing, even a 60F versus 70F room creates major behaviour differences on some gaming LCDs -- especially VA LCDs moreso than TN LCDs, though TN is affected to an extent. Things like worse/better strobe crosstalk to worse/better inversion artifacts, etc.

No, changing cable does not help. It's definitely panel. It's law of physics based on how the panel is made.

You studied electronics class in High School or University? OK. It's very hard for a panel to distribute exactly the same amount of electricity to every pixel on the screen when overclocked -- we're talking about sub-millivolt differences between edges of a screen -- a difference of less than 0.001 volt on a pixel creates human-visible greyscale differences. And it also interacts with the LCD inversion logic (inverse polarities for even/odd scanlines) since the negative voltages is not always a perfect mirror of the positive voltages, and the ratio of difference can vary for left/right edges or top/bottom edges, due to the length of microwires from edge of screen to the pixels. There's thousands of microwires etched into the glass in a grid behind the pixels, to drive the pixels. And they aren't perfect when overclocked. And Ohm's Law (I = V / R) is a royal PITA the farther away from the edge you get, since those tiny wires have more resistance for pixels further away from the voltaged edge. It's goddamned difficult to have perfect LCD GtG voltages for every single subpixel on the entire surface of a panel. And in a different panel batch, those same microwire grids may not have exactly the same precision resistance (to the umpteenth decimal digit) and different artifacts appear. Ain't panel lottery a hairpulling thing sometimes, eh?
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Re: Acer XB241H scanlines at 144hz and up

Postby Kosmos » 08 Oct 2018, 01:17

This monitor is pretty bad and has a lot of issues that I returned mine. The scanlines are standard for this panel and it will appear on any unit of the model.
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Re: Acer XB241H scanlines at 144hz and up

Postby Pride » 08 Oct 2018, 03:31

Thank you both, that's very sad to hear. For now, I have decided to keep the monitor and manually swap between 100hz (when browsing, watching videos, etc) and 144hz (when gaming).

Chief Blur Buster wrote:You can try reduced vertical totals to slow down the panel scan as much as possible, but there's a point where it doesn't help.

What exactly are vertical totals and how could I reduce them?

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