Monitor Response Time Explained: GtG, Ghosting and Overdrive
What monitor response time means, how GtG and MPRT differ, why ghosting and smearing appear, and how overdrive settings and refresh rate change motion clarity.
Response time is how long a pixel takes to change from one colour to another, usually printed on the box in milliseconds. Short response times keep moving objects crisp; long ones leave faint trails behind them. The figure matters most on fast, high refresh-rate monitors, where each frame is on screen only briefly and slow pixels never quite catch up.
What the number on the box measures
Most manufacturers quote GtG, or grey-to-grey: the time a pixel needs to shift between two shades of grey. It is a useful shorthand, but there are caveats worth knowing:
- The headline figure usually reflects the fastest transition the panel manages, often with the most aggressive overdrive setting switched on.
- Some transitions, especially from very dark to slightly lighter shades, can take considerably longer than the advertised number.
- Manufacturers do not all measure the same way, so two "1 ms" monitors can look quite different in motion.
A second figure, MPRT (moving picture response time), describes how long an image stays visible to the eye before the next one replaces it. It is closely tied to refresh rate and to backlight strobing, which comes up further down.
Refresh rate vs response time
The two specs are often confused, because both relate to motion. They answer different questions:
| Refresh rate | Response time | |
|---|---|---|
| Question it answers | How often does the screen draw a new image? | How quickly can each pixel reach its new colour? |
| Unit | Hertz (refreshes per second) | Milliseconds |
| Better when | Higher | Lower |
| What goes wrong | Low values make motion look stepped | Slow values leave trails and blur |
They also depend on each other. At 144 Hz a new frame arrives roughly every 6.9 ms. If many pixel transitions take longer than that, they are still changing when the next frame lands, and the extra refreshes buy less clarity than the spec sheet suggests. Frame rate enters the picture too, since a fast screen only helps when the game feeds it enough frames; our guide to FPS in gaming explains that side.
Ghosting, smearing and overshoot
Ghosting
A faint, translucent copy trailing behind a moving object, such as a cursor or a crosshair swinging across a bright sky. It means pixels are lagging behind the image they should be showing.
Dark smearing
Murky streaks when dark objects move across darker backgrounds. This is typical of panels whose dark transitions are slow, and it shows most in night scenes and dim interiors.
Overshoot, or inverse ghosting
A bright or coloured halo that appears when pixels are pushed too hard and briefly go past the target colour. It usually looks like a light outline behind dark objects.
Not every trail is the monitor's fault. Upscalers can leave their own faint streaks behind small, fast details, which our article on DLSS and image upscaling covers. A quick test is to switch the upscaler off and see whether the trail goes with it.
Overdrive: the setting that speeds pixels up
Overdrive, sometimes called response time compensation or trace free, briefly applies a stronger voltage so pixels change faster. Monitors usually offer several levels, from off through to an extreme mode. The trick is finding the strongest level that does not create overshoot:
- Set the monitor to its highest refresh rate and confirm the operating system uses it.
- Open something with high-contrast motion, such as scrolling text, a game menu with moving elements or a slow camera pan.
- Step through the overdrive levels one by one and watch the edges of moving objects.
- Keep the level where trails are shortest without bright halos appearing.
Some monitors tune overdrive for one refresh rate. With variable refresh rate switched on, the frame rate moves around, and a level that looks perfect at the top of the range can overshoot lower down. Monitors with variable overdrive adjust automatically, which is one reason sync settings and pixel response are worth reading about together; see our explainer on V-Sync, G-Sync and FreeSync.
Panel types in broad strokes
- TN: traditionally quick pixel response, weaker viewing angles and colour.
- IPS: good colour and angles; modern fast IPS panels respond quickly enough for most competitive play.
- VA: strong contrast and deep blacks, but dark transitions are often slower, which is where smearing comes from.
- OLED: each pixel emits its own light and changes almost instantly, so trailing from pixel response is rarely a concern.
These are tendencies, not rules. Individual models vary widely, so detailed reviews that test motion are more useful than the panel type alone.
Blur that is not response time
Even a screen with instant pixels shows some blur. Your eyes track a moving object smoothly while the display holds each frame still until the next one, and that mismatch smears the image. Higher refresh rates shorten the hold. Backlight strobing, offered on many gaming monitors under various names, flashes the backlight briefly for each frame to cut this persistence, at the cost of brightness and sometimes visible flicker.
Short answers
Do you need a 1 ms monitor?
Not necessarily. Consistent, well-tuned response across many transitions matters more than the headline figure. For slower games, a quoted 4 or 5 ms rarely bothers anyone. In fast games, the rest of the chain counts as well, from a responsive mouse to the other desk gadgets PC players rely on.
Is response time the same as input lag?
No. Input lag is the delay before the screen starts showing a new image; response time is how long the pixels take to finish changing once it has. Both add to how quickly a game feels, but they are measured separately.
Does screen size affect response time?
Not directly, but larger screens make trails easier to notice. If you are still choosing a display, our guide to the best monitor size for gaming helps match size, resolution and distance.
