Monitor ghosting and motion blur test
Follow one of the moving shapes with your eyes as it crosses. A slow panel leaves a smeared trail behind the shape; overdrive set too aggressively leaves a pale halo in front of it.
This is a test you judge by eye. A browser cannot measure pixel response time - that needs a high-speed camera - so no figure in milliseconds is shown here, because any such number would be invented. What this does is present a properly controlled moving stimulus, which is the part that is hard to arrange yourself. If the frame rate above is not steady, what you are seeing is dropped frames rather than your panel.
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Ghosting, and its opposite
When a pixel cannot change colour quickly enough, a moving edge drags a faint copy of itself behind it. That is ghosting, and it is what "response time" describes.
Manufacturers counter it with overdrive, which briefly overshoots the target voltage to force the pixel to switch faster. Pushed too far, the pixel overshoots the colour as well and leaves a bright halo in front of or around the object. That is inverse ghosting, or overshoot, and it looks worse than the problem it solves.
Which one you have decides what to do, and they are easy to tell apart once you know to look: a trail behind means turn overdrive up, a halo in front means turn it down.
How to look
- Press Start and follow one shape with your eyes as it crosses. Staring at a fixed point shows you something different - your eye's own motion is part of how this is perceived.
- Start at the default speed. Faster is not better; too fast and everything smears on every panel.
- Try all three backgrounds. Dark-to-light transitions are usually the slowest, so a fault often shows on one background and not another.
- Check the frame rate reading. If it is not steady, you are looking at dropped frames rather than at your panel.
Adjusting overdrive
In your monitor's own menu the setting is rarely called overdrive. Look for Response Time, Trace Free, OD, Rampage Response or AMA, depending on the manufacturer. Change one step at a time and re-run this test after each.
The middle setting is usually the best on most monitors. The highest is very often worse than the middle, because it trades a trail you barely notice for a halo you do.
Note also that on many monitors the ideal overdrive setting changes with refresh rate - a level that is right at 144 Hz can overshoot badly at 60 Hz.
What this test cannot tell you
It cannot give you a response time in milliseconds. Measuring that requires a high-speed camera or a photodiode pointed at the panel; no software running inside a browser can do it, and any page that displays such a number is inventing it. What a browser can do well is present a properly controlled moving stimulus at a known speed - which is the part that is hard to arrange at home - and let you judge with your own eyes.
Related checks
The refresh rate test measures how many frames a second your monitor presents, and the monitor test covers static faults - dead pixels, backlight bleed, tint and banding.
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