Monitor ghosting and overdrive: how to test and fix it

How to test your monitor for ghosting

Open the motion blur test. It moves small, high-contrast UFOs across the screen at a fixed speed, so you can see blur, ghosting and overdrive trails by eye. It's the same idea as the well-known UFO test.

1. Close other tabs and apps, and keep the test tab in front so the browser doesn't drop frames.
2. Check the Frame rate reading matches your monitor's refresh rate. If a 144Hz monitor reads 60, fix that first.
3. Follow the top UFO with your eyes as it moves, rather than staring at one spot. The rows below move at half and a quarter of the speed.
4. Look at the edges: a soft smear is blur, a faint copy behind it is ghosting, and a bright or dark outline is overdrive overshoot.
5. Switch between the Dark, Mid grey and Light backgrounds, and try speeds from 240 to 1920 px/s.
6. Change one monitor setting at a time and look again.

The test shows the artefacts so you can compare settings. It doesn't measure response time in milliseconds. A browser can't see how fast pixels change; that needs a camera or a light sensor.

What is ghosting, motion blur and inverse ghosting?

• Motion blur is a soft, smeared edge on anything that moves. Part of it comes from your eyes: on most monitors each frame stays lit for the whole refresh, so as your eye follows a moving object, the still image smears across your retina. Slow pixels make it worse.
• Ghosting is a distinct faint copy, or several, trailing behind the object. It happens when pixels take longer than a frame to change colour, so the old image is still fading when the new one appears.
• Inverse ghosting, or overshoot, is a bright or coloured halo, often behind or around the object. It's caused by overdrive pushing pixels too hard, so they go past the target colour before settling.

Most monitors show a little of each. What matters is whether it bothers you in the games and apps you use.

How to read the motion blur test

Trails behind the UFO that look like a darker or lighter copy of it mean slow pixel transitions. Raising overdrive usually shortens them.

A bright, glowing or coloured outline that wasn't in the original image means overshoot. Lowering overdrive usually removes it.

Results often change with the background. Pixels move between some shades faster than others, so a monitor can look clean on the light background and smeary on the dark one. Dark transitions are often the slowest on VA panels, which is why dark-scene smearing is a common complaint about them.

Check the Step reading too. It shows how many pixels the UFO jumps each frame. A bigger jump means more blur, which is why the same speed looks sharper on a faster monitor. If the Dropped count rises, the browser is skipping frames and the motion will judder whatever your settings.

Step per frame at 60 Hz and 960 px/s

16 px

Step at 144 Hz (960 ÷ 144)

6.7 px

Step at 240 Hz (960 ÷ 240)

4 px

How to fix ghosting: overdrive settings

Overdrive drives each pixel with a higher voltage for a moment so it changes colour faster. Monitor makers give it their own names, such as Response Time, Trace Free or OD, but it's in the on-screen menu on almost every gaming monitor.

1. Open the monitor's on-screen menu and find the overdrive or response time setting. Note the current level.
2. Keep the motion blur test running on the dark background at 960 px/s.
3. Step through each overdrive level, from off to the highest, and watch the trail and the edges.
4. Pick the highest level that shortens the trail without adding a bright halo. On many monitors this is a middle setting, not the maximum.
5. Check the mid grey and light backgrounds, which can show overshoot that the dark one hides.

Some monitors tune overdrive for their top refresh rate. If you also use a lower rate, or variable refresh with games running below the top rate, a level that looks clean at full speed can overshoot at lower rates. Test at the rate you actually play at.

Why higher refresh rates reduce blur

At 60Hz each frame stays on screen for about 16.7 ms. At 144Hz it's about 6.9 ms, and at 240Hz about 4.2 ms. The shorter each frame, the less the image smears as your eye follows it, and the smaller the jump between positions. That's why the same UFO looks sharper on a faster monitor, even with identical pixels.

Pick your refresh rate and a test speed to see the frame time and how far an object jumps each frame:

This only helps if the monitor is really running at its top rate. Many ship set to 60Hz, and the wrong cable can cap them. Measure it with the refresh rate test, or the 144Hz test and 240Hz test for those monitors. If it's stuck lower, follow our guide to a 144Hz monitor showing 60Hz.

Backlight strobing and motion blur reduction

Many gaming monitors have a blur reduction mode that flashes the backlight once per frame instead of leaving it on. You see each frame for a shorter moment, which cuts the eye-tracking blur that overdrive can't fix. Makers call it things like ELMB, ULMB, DyAc or MPRT mode.

• It makes the screen dimmer, because the backlight is off part of the time.
• It usually only works at fixed refresh rates and often can't be used with variable refresh such as G-Sync or FreeSync.
• Some people notice flicker, especially at lower refresh rates.
• It can show a doubled image called strobe crosstalk, often worse at the top or bottom of the screen.

Turn it on, run the motion blur test again and compare. If the UFO is clearly sharper and the trade-offs don't bother you, keep it.

Other things that cause trails

• Picture modes: some presets change overdrive or add processing. Try the monitor's standard or gaming mode.
• TVs: turn on Game mode, which turns off motion smoothing and image processing that add delay and artefacts.
• Dropped frames: if the Dropped count rises, close other apps and tabs. Juddering motion isn't a panel problem.
• Cold panels: LCD pixels respond more slowly when the monitor is cold, so give it a few minutes to warm up before judging.

OLED vs LCD

OLED pixels change almost instantly, so OLED monitors show very little ghosting or overshoot and don't need overdrive. They still show eye-tracking blur, because each frame stays lit for the full refresh, so a higher refresh rate still makes them sharper.

LCD panels vary. Fast IPS and TN panels usually ghost little with a well-tuned overdrive setting, while VA panels often smear in dark scenes. If you're choosing a monitor, a high refresh rate and good overdrive tuning matter more than the response time printed on the box.

Next, check your refresh rate and screen

Confirm your monitor is running at its full speed with the refresh rate test, then check your screen resolution is set to native, since a scaled image looks softer in motion too. For the rest of the display, the screen resolution guide explains scaling and pixel ratio.