Motion blur and ghosting test: UFO style
Follow a moving square with your eyes and look for a smeared trail. The test shows how sharp motion looks on your monitor and works out the blur caused by your refresh rate at the speed you choose.
What the UFO motion test shows
The original UFO test from Blur Busters moves a picture across the screen at a fixed speed so you can see how clear it stays. This page does the same with a bright square. Follow it with your eyes and note how sharp the edges look. A soft smear along the edges is motion blur. A faint copy of the square trailing behind it is ghosting. A dark or light halo is overshoot from overdrive.
Run all three speeds. Slow motion hides problems, while fast motion makes any trail obvious. Switch the background between stripes, black, grey and lines to see which combination reveals most. Dark and mid grey backgrounds show slow pixel response best, while the stripe pattern shows persistence blur clearly.
Hold blur by refresh rate
Blur width in pixels while tracking an object at 960 pixels per second, from speed divided by refresh rate.
| Refresh rate | Frame time | Hold blur |
|---|---|---|
| 60 Hz | 16.7 ms | 16 px |
| 120 Hz | 8.3 ms | 8 px |
| 144 Hz | 6.9 ms | 6.7 px |
| 240 Hz | 4.2 ms | 4 px |
| 360 Hz | 2.8 ms | 2.7 px |
Persistence blur and refresh rate
Most screens hold each frame for the whole frame time, which is called sample-and-hold. When your eyes track a moving object, the held image smears across your retina by the distance the object moves during one frame, even if the pixels switch instantly. That distance is speed multiplied by frame time. At 960 pixels per second on a 60 Hz screen the blur is 16 pixels wide, on 144 Hz it is about 7 and on 360 Hz it is under 3.
This is why higher refresh rates look sharper in motion and why strobing backlights, which show the image for only a part of each frame, can look clearer still at the cost of flicker and brightness. The panel shows the figure for your measured rate and the table compares other rates.
Getting a cleaner picture
If you see a long dark trail, your pixels are slow, and raising overdrive one step may help. If you see bright halos or coloured edges, overdrive is too strong, so lower it. Check that the screen runs at its full refresh rate with the refresh rate checker. For the maths behind pixel speed, use the response time calculator.
Finally, remember that game frame rate matters too. A 240 Hz monitor only gives 240 Hz clarity when the game runs near 240 frames per second. A dead pixel check with the dead pixel test is a good next step on a new screen.
How to use the motion blur test
- Choose a speed. Start with medium, then try fast.
- Pick a background pattern.
- Press Start motion and follow the square with your eyes.
- Look for a smear, a trail or a halo behind the square.
- Compare the blur figure with your refresh rate and change the overdrive setting if needed.
Common mistakes to avoid
- Staring at a fixed point instead of tracking the square.
- Judging a monitor at one slow speed that hides blur.
- Turning overdrive to maximum and trading blur for halos.
Related tools and guides
Keep going with these: Response time vs refresh rate calculator, Refresh rate checker, Dead pixel test, Frame pacing and stutter test, does frame generation add input lag.
Frequently asked questions
What is the UFO ghosting test?
It moves a picture across the screen at a fixed speed so you can see motion blur and trails. You follow the moving object with your eyes. A smear means blur, a faint copy behind it means ghosting, and bright edges mean overdrive overshoot.
What is the difference between motion blur and ghosting?
Motion blur is a general softening of moving edges caused by slow pixels or by the way the screen holds each frame. Ghosting is a visible trail or copy behind a moving object, usually from slow pixel transitions. Both improve with faster panels.
Does a higher refresh rate reduce blur?
Yes. On a sample-and-hold screen the blur width equals speed multiplied by frame time, so doubling the refresh rate halves it. The pixels must also respond fast enough, otherwise the trail comes from slow pixels instead of the hold effect.
What is overdrive on a monitor?
Overdrive pushes pixels harder to change colour, which shortens response time and cuts ghosting. Too much causes overshoot with bright or dark halos behind moving objects. A middle setting is usually the best compromise, and many monitors offer an adaptive mode.
Does this replace a camera-based motion test?
No. This is a quick visual check with a calculated blur figure. Camera-based tests photograph the moving square with a controlled shutter and measure trails more precisely. Use this page to compare settings on your own screen and spot big problems.
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