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Input Lag when using 240hz screens in 120hz mode

Posted: 10 Jan 2021, 10:37
by Jestaz
Hello everyone,

i do have two 240hz screens for pc gaming:

The AW2518hf (240hz, 1080p)
The Omen x 27 (240hz 1440p)

For Pc gaming both have really low response time and input lag, however i want to use one of those monitors for my xbox series s and was wondering which of the two does have lower input lag when running in 120hz mode?

Since Chief mentioned that some 240hz screens can have quite a bit of input lag when not running in 240hz mode.
I saw the rtings input lag test for my omen x27 and the input lag @60hz was around 15ms if i remember correctly. For my AW2518hf i didn't find any specific tests on rtings, however newer models of the same brand (AW2521HF) seem to have below 10ms when running @60hz.
So how bad is the input lag really on those screens? I don't really want to buy a 144hz screen just for the series s.

Also what can i potentially do on my side to reduce input lag when playing on the series s? Even if the input delay is worse in 120hz mode, how much worse is it compared to a 144hz screen?

Re: Input Lag when using 240hz screens in 120hz mode

Posted: 10 Jan 2021, 14:35
by Chief Blur Buster
This is very screen-dependant.

I have seen some 240Hz panels that is low lag at all refresh rates (perfect horizontal scanrate sync between cable & panel -- the pixels literally stream from the cable straight to the screen, one pixel row at a time, in sync, at all refresh rates).

But as a general rule of thumb, a 240Hz panel with bad 60Hz lag, will have slight 120Hz lag (an average of 0.5/120sec delay).

However, this can be solved if you're playing PC games rather than gaming console -- 120fps cap at 240Hz VRR will always have low lag.

Re: Input Lag when using 240hz screens in 120hz mode

Posted: 11 Jan 2021, 12:30
by Jestaz
Thanks for your answer Chief, i really appreciate it. This game (Halo 5) is not on pc, so i have to play it on console. I prefer to play any game on my pc though and i got the screens almost purely for pc gaming.

i looked my Omen x27 up on rtings ( and it seems to have low input lag and response time when running on 240hz native res. However @60Hz it seems to be around 15ms input lag.

- Is that still somewhat low lag, or is this bad?
- Also i am currently using a HDMI audio converter in order to use optical audio on the Xbox Series S. Would using this converter introduce
further input lag?
- How is input lag when running my 1440p omen x27 in 1080p and 120hz? Does downscaling introduce input lag usually?
- Are there any 144hz screens that would beat my omen x27 or AW2518hf regarding input lag and response time combined on the Xbox series s?

I assume a lot of my questions are rather specific to my display model, as you already pointed out.

Re: Input Lag when using 240hz screens in 120hz mode

Posted: 13 Jan 2021, 07:58
by TTT
Its because some monitors don't use the same scaler across DP and HDMI, its pretty much the equivalent of using 2 different screens.

I had the XB252Q 240hz gsync monitor, you could only get over 60 with DP.

The HDMI port used a completely separate scaler so it maxed at 60 and has alot more input lag than the DP scaler at any fps, also the console/PC basically recognised it as a TV, not a monitor.

Re: Input Lag when using 240hz screens in 120hz mode

Posted: 15 Jan 2021, 09:01
by Jestaz
Thank you for explaining. So i assume unless the monitor is listed under rtings, or i test it myself, there is almost no way to determine what input lag or response time a certain monitor will have when running with non native Hz modes?

I was also wondering if a dedicated 60hz Monitor like the Benq RL2455HM would have less input lag on the Xbox Series S, than my current Monitors. Even though it is way older and outdated and doesn't take advantage of the 120hz mode of the Series s, is it still superior input lag wise?