Response Time vs Input Lag: They're Not the Same

These two specs get mixed up constantly. They measure different things.

Response time (pixels)

How long a pixel takes to change color, in milliseconds (ms), usually gray-to-gray (GtG). Slow response → ghosting/blur. Test it visually with the Ghosting Test. "1ms" claims are best-case; real-world is often higher.

The reason marketing numbers and real behavior diverge so much is that GtG is not one number. A panel changes between dozens of different shade pairs, each at its own speed, and manufacturers are free to quote the fastest transition at the most aggressive overdrive setting. Dark transitions are usually the slowest, which is why a monitor rated 1ms can still smear badly in a dark game scene.

You'll also see MPRT quoted in milliseconds. That's a different thing again — it describes how long a frame is held in front of your eye, not how fast the pixel changes. A low MPRT figure almost always assumes backlight strobing is switched on. More on that in motion blur reduction.

Overdrive, and its trap

Overdrive pushes extra voltage at a pixel to make it change faster. Set too high, it overshoots the target shade and leaves a bright halo trailing the object — inverse ghosting, which looks worse than the blur it was meant to fix. Most monitors label it Overdrive, Response Time, Trace Free or OD, with settings like Off / Normal / Fast / Extreme.

Find your best setting empirically: run the Ghosting Test, step through each overdrive level, and pick the one just below where light halos appear. The right level often changes with refresh rate, so re-check after changing that.

What differs by panel type

| Panel | Typical motion behaviour | | --- | --- | | TN | Fastest transitions, weakest colors and viewing angles | | IPS | Fast enough for most gaming; some dark-transition smear | | VA | Strong contrast, noticeably slow on dark-to-dark — the classic "black smear" | | OLED | Near-instant pixel transitions; remaining blur comes from persistence, not response |

IPS vs VA vs TN vs OLED covers the wider trade-offs.

Input lag (system)

The delay between an input (mouse/keyboard) and the result showing on screen. It's the sum of:

• Mouse polling and USB delay.
• Game engine and render time.
• Display processing (scaler, image enhancements).

High input lag makes a game feel "floaty" even at high frame rates.

The largest and most fixable chunk for most people is display processing. TVs are the worst offenders: motion interpolation, noise reduction and upscaling all buffer frames before showing them, and that buffering is exactly what Game Mode disables. On monitors the processing is lighter but still real, especially if the input signal needs scaling to fit the panel's native resolution.

Frame rate matters too, and independently. At 30 frames per second, a frame exists for over 30ms before the next one can replace it, so no monitor setting makes that feel responsive. Raising frame rate lowers the average wait for a fresh frame.

How to reduce input lag

• Enable the monitor's Game Mode (it bypasses image processing).
• Turn off dynamic contrast, motion smoothing, and noise reduction.
• Use a wired mouse with a high polling rate.
• Cap your frame rate slightly below your refresh rate when using V-Sync, or use adaptive sync.
• Run the display at its native resolution, so nothing has to be scaled.
• Confirm the panel is actually running at its rated refresh rate — plenty of monitors ship set to 60Hz. See how to enable your full refresh rate and verify with the Refresh Rate Test.

Traditional V-Sync adds the most lag of any common setting because frames wait for the next refresh. Adaptive sync — G-Sync or FreeSync — avoids most of that while still removing tearing; screen tearing, V-Sync, G-Sync and FreeSync explains which combination to use, and the Screen Tearing Test shows whether yours is working.

Telling them apart in practice

Both problems ruin motion, but they feel different, and the distinction points at different fixes.

• Trails behind moving objects, blur on text while scrolling, smearing in dark scenes — that's response time. Adjust overdrive; see what is ghosting and how to fix it.
• The image is sharp but the cursor or the aim feels like it's dragging behind your hand — that's input lag. Chase Game Mode, processing settings, sync settings and frame rate.

A quick way to separate them: move the mouse in circles on the desktop. If the cursor looks clean but arrives late, you have lag. If it smears, you have slow pixels.

Bottom line

Fast response = clearer motion. Low input lag = more responsive feel. For competitive play you want both — and a high refresh rate on top. If you're deciding how much refresh rate is worth paying for, 60 vs 120 vs 144 vs 240Hz puts the differences in order.