What monitor input lag is

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Feel like your shots land a beat late? Monitor input lag might be part of it. It’s the wait after the PC has sent a frame, before the panel begins to show it. For full picks, see the best gaming monitors. Response time is how long a pixel takes to change shade after the picture has started. A 1 ms line on the box is one lab transition. It is not this wait, and it is not the time from a click to the screen.

I play Overwatch as Zarya on a 1080p 240 Hz panel, and I keep a 1440p 155 Hz panel for everything that wants more pixels. The desktop is an RTX 5080 and an AMD Ryzen 9 9950X3D2. More monitor guides.

The details below come from VESA, NVIDIA, HDMI and maker pages, so check the current listing before you buy.

Where the clock starts

Where the clock starts

At the clickAfter the frame leavesAs the pixel changes

This wait is the panel's input lag. It starts when the frame has left the PC and ends when the panel begins the picture. The 1 ms on the box is not this wait.

Panels worth a look

These three are official SKUs whose makers publish a lag note. They are examples of a clock, not my two screens.

• A maker that prints an input-lag millisecond: ASUS ROG Strix XG248QSG Ace. Official ROG US page: 24.1-inch FHD Super TN, 610 Hz overclocked, 0.1 ms response (min.), 0.8 ms input lag. ASUS Store Price $799.00. That 0.8 ms is ASUS’s claim. It is not a test I ran. ROG US page. Amazon search for XG248QSG Ace
• A measurement display Worth a look: ASUS ROG Swift PG27AQN. Official: 27-inch 1440p, 360 Hz, Fast IPS, 1 ms GtG, G-SYNC, NVIDIA Reflex Latency Analyzer on the red USB port. The manual times a click until a pixel change such as a muzzle flash and calls that PC + Display Latency. ROG US page. Amazon search for PG27AQN
• Example: LG UltraGear 27GR83Q-B. Official US page: 27-inch 1440p IPS, 1 ms (GtG) with 240 Hz, G-SYNC Compatible, FreeSync Premium. LG calls Dynamic Action Sync the feature that reduces input lag and does not print a millisecond next to that line. LG US page. Amazon search for 27GR83Q-B

The short version: read which clock the number used. The 1 ms on the box is not this wait.

Three clocks that share one name

NVIDIA’s introduction of Reflex, 1 September 2020, is blunt about the naming mess. “Input lag” shows up on a mouse box, on a monitor box, and in a game overlay. The company then splits the path.

Peripheral latency is the mouse. Game latency is the CPU submitting a frame. Render latency is the GPU queue. PC latency is game plus render. Display latency is the time the display takes to present a new image after the GPU has finished the frame. System latency is the whole trip, click to pixel.

I use the middle of that stack. The frame has left. The panel has not begun the picture. That is the monitor’s own wait before a new image starts. It is not the mouse. It is not the time the RTX 5080 spent finishing the frame. It is not the gray-to-gray line.

BenQ’s official input lag versus response time explainer uses the longer clock: press to action on screen, with response time inside that path. HDMI and DisplayPort, BenQ writes, have the same speed. The processing after the signal arrives is the wait you can switch.

LG UK’s input lag for gaming guide uses that longer clock too. The company says competitive players try to stay under 15 milliseconds, casual play under 40, and that a delay past 50 becomes more noticeable. That is LG’s guidance. It is not a number I measured on the 240 Hz screen or the 155 Hz screen.

A test that ends on a muzzle flash started at the click. NVIDIA’s Reflex Latency Analyzer is that test. It includes the mouse and the PC. It is not the panel’s wait by itself.

The floor the refresh sets

A new picture cannot start until the panel is ready for one. The gap between those starts is 1000 divided by the hertz. At 60 Hz the gap is about 16.7 milliseconds. At 120 Hz it is about 8.3. At 144 Hz it is about 6.9. At 155 Hz, the sharper screen I actually use, it is about 6.5. At 240 Hz, the Overwatch screen, it is about 4.2. At 360 Hz it is about 2.8.

NVIDIA’s system latency guide splits display latency into three pieces: scanout, display processing, and pixel response. Higher Hertz, that page says, reduces scanout latency. Enable the maximum refresh rate in NVIDIA Control Panel. That gap is how long you may wait for the next start. It is not a processing delay, and it is not the lag a review prints unless the review says the clock is that gap.

Processing sits on top of the floor. A panel can hold a frame and add more than one gap. A higher rate shortens the schedule. It does not erase a processing wait, and it does not finish a frame the PC has not drawn. FPS monitor notes is the Hertz and resolution page after this wait is settled.

What VESA actually certifies

VESA does not sell an “input lag” logo. The association’s public tests sit next to this wait, and they are easy to mash into it.

The DisplayHDR CTS, Revision 1.1, draws a useful line. Display latency is the processing delay after the GPU signal before the brightness change starts. Rise time is how long the display then takes to go from about 10 percent to 90 percent of peak-white luminance. Figure 8-1 on that spec shows a two-frame processing delay labeled display latency, then a separate rise time. The spec says the actual latency is not of consideration for the rise-time test. A DisplayHDR badge is a brightness and rise-time exam. It is not a published input-lag millisecond.

The Adaptive-Sync Display CTS, launched 2 May 2022, says the AdaptiveSync Display tier is optimized for gaming with a large variable-refresh range and low latency. The public mandate table still tests gray-to-gray, overshoot, flicker, and jitter. AdaptiveSync Display asks for a maximum at or above 144 Hz and an average of 20 gray-to-gray tests at or under 5 ms with factory-default overdrive. That 5 ms is response time. It is not this wait.

ClearMR grades motion blur as a ratio of clear pixels to blurry pixels. A ClearMR badge is not a faster start. Motion blur reduction is the strobe page.

What game mode is doing

Image processing is the part of the panel’s wait you can sometimes switch off. Motion smoothing, sharpening, dynamic contrast, and a heavy picture treatment are work the set does after the signal arrives. BenQ’s rule is short: image processing means lag. Even if the gray-to-gray line is 1 ms, HDR, dynamic brightness, edge sharpening, and local dimming still add wait. Local dimming is a brightness decision. It is not a faster pixel.

The menu name is whatever the manual uses. Game mode and PC mode are the usual labels. BenQ recommends those modes because they switch most of that work off. LG UK describes Game Mode the same way: processors polish each frame for movies, and Game Mode turns that polish down or off.

HDMI Auto Low Latency Mode is the automatic version of that menu. A console or a PC sends a signal, and the display switches to a low-latency mode. When the source no longer needs it, the picture treatments come back. ALLM is a switch. It is not a new Hertz.

LG UltraGear pages print Dynamic Action Sync as the feature that reduces input lag. The 27GR83Q-B is one of those panels. LG does not put a millisecond on that line.

Turn the treatments off, then look at the same scene. Two changes at once will not tell you which one added the wait. A trail behind a moving object is the pixel still changing. That trail is response time, not this wait.

Variable refresh, VSync, and Reflex

VRR and G-Sync change how often a new picture is allowed to start. The panel can wait for a late frame instead of tearing. That is not a faster pixel, and it is not a shorter processing queue by itself. VESA’s AdaptiveSync logo is the open test for that range. G-SYNC is NVIDIA’s name for the same job, with or without NVIDIA’s processor in the set.

NVIDIA’s latency guide still tells you to turn VSync off if you will accept tearing, because VSync pushes wait back through the whole PC. On a G-SYNC panel, the same page says you can keep VSync on with Reflex, or with Ultra Low Latency Mode, and the driver will cap the frame rate below refresh so the old queue does not pile up. That combo is a little slower than uncapped Reflex with tearing allowed. I play on the 240 Hz screen for Zarya.

NVIDIA Reflex is the in-game line that holds the CPU until the GPU can take the next frame. Overwatch is on NVIDIA’s Reflex-compatible list. Reflex does not replace game mode on the monitor.

NVIDIA also prints a G-SYNC Esports mode on Analyzer displays. The latency guide says that mode turns off settings such as a variable backlight so display processing stays short. The PG27AQN manual tells you to set that mode before you trust the Analyzer rectangle.

How NVIDIA measures the long clock

If you want a number from a click, NVIDIA’s official tool is Reflex Latency Analyzer. It lives in certain G-SYNC displays. The PG27AQN is one. You plug a mouse into the marked USB port. The analyzer waits for a bright pixel change, usually a muzzle flash, and prints PC + Display Latency. A listed Reflex mouse can add peripheral latency and give full system latency.

That clock is longer. It includes the mouse, the game, the render queue, scanout, processing, and the pixel’s own change. NVIDIA Research, in the same 2020 post, published that a 12 ms system versus a 20 ms system changed aim-trainer completion by 182 ms on average. That pair is NVIDIA’s study.

What to compare, and what to switch

Compare two monitors only when the clock, the rate, and the mode match. A figure taken at 60 Hz in a game mode is not the same figure at 144 Hz, and it is not a click-to-picture test. The box’s 1 ms does not belong in that column. If the review does not say where the clock started, the number is unfinished.

BenQ says makers can test response time in the factory, and that input lag is harder to print because so much of the long clock is not the panel. That is why a gaming box almost always shows 1 ms GtG and almost never shows this wait. ASUS printing 0.8 ms on the XG248QSG Ace is the exception. Treat it as that maker’s claim on that SKU.

Adding frame time, refresh interval, and poll interval is the input-lag budget calculator. That sum is still not the panel’s own delay, and it is not NVIDIA’s click-to-photon test.

What you can switch without a lab:

1. Set the Hertz you actually play. NVIDIA: higher Hertz reduces scanout.
2. Open game mode, PC mode, or G-SYNC Esports mode. Turn motion smoothing, extra sharpening, dynamic contrast, and local dimming off while you judge the wait.
3. Use the port that holds that Hertz. BenQ: HDMI and DisplayPort are the same speed.
4. Leave VRR on if you want the panel to wait for a late frame. Read VRR for the range.
5. Set Reflex On when the game lists it. That is the PC queue, not the panel.

A missing lag number is an incomplete listing, not a slow panel. A trail is the other page. A late click that includes the mouse is NVIDIA’s long clock. Prices move. A listing is a clock, a rate, and a mode.

Read the clock, set game mode, then buy the Hertz the PC can fill. More monitor guides.

Common questions

What is monitor input lag?

The delay between your PC sending a frame and the monitor starting to show it. It's different from the 1 ms response time printed on the box.

What is a good input lag for gaming?

Under about 15 ms is great for competitive play, and under 40 ms is fine for casual games. Above 50 ms becomes noticeable.

Is input lag the same as response time?

No. Response time is how fast pixels change color. Input lag is how long it takes for a frame to start appearing at all.

Does a higher refresh rate reduce input lag?

Yes, somewhat. A higher refresh rate means each new frame can appear sooner, which cuts part of the delay.