Three links in the chain
Input lag, also called system latency, is the time from your mouse click to the result on screen. NVIDIA splits it into three parts:
- Peripheral latency: how long your mouse or keyboard takes to sense and report the input. Mice and keyboards range from about 1 ms to 20 ms
- PC latency: the operating system, the game and the rendering. It's often the largest part
- Display latency: scanout, any image processing in the screen and the pixel response
A monitor spec sheet only speaks for the last link. Fixing the display won't touch the other two.
The small wins on the input side
A mouse reports its position on a schedule called the polling rate. At 125 Hz that's a report every 8.00 ms, and at 1000 Hz it's every 1.00 ms. NVIDIA estimates a 125 Hz rate adds up to 3 ms of latency on average compared with 1000 Hz. That's a cheap fix, and NVIDIA recommends setting the polling rate to the maximum.
Higher DPI doesn't mean lower latency, NVIDIA says, and your sensitivity setting won't change it much either.
What the display adds
Scanout is the time the screen spends drawing a new image, and it shrinks as the refresh rate rises. One refresh lasts 16.67 ms at 60 Hz, 6.94 ms at 144 Hz and 4.17 ms at 240 Hz. In general, NVIDIA says, raising the refresh rate is the best way to cut display latency.
The other two display parts are processing and pixel response. Image processing takes time, and upscaling and motion smoothing, common on TVs, add delay. As a rough guide, under 30 ms is generally considered unnoticeable on a television, and about 200 ms overall is distracting. The last part, pixel response time, is how long the pixels take to settle.
Sync settings trade lag for tearing
V-Sync waits for the screen, and that wait backs up through the whole system. NVIDIA recommends turning it off if you can live with tearing.
On a G-Sync display you can keep V-Sync on and avoid the tearing. NVIDIA suggests pairing it with Reflex or Ultra Low Latency Mode, which caps the frame rate below the refresh rate and avoids the back pressure. That still adds slightly more latency than running uncapped with Reflex.
Milliseconds matter most in fast shooters. In a slow strategy game you'll rarely notice them, so don't chase them there.