Ghosting test

A hard edged block moving across a grey field, which is where smearing and overshoot show up.

Escape or one tap comes back.

Every colour, one tap away

Brightness, timer and colour cycle

What ghosting is

Liquid crystal takes time to change state. When a moving object crosses the screen faster than the pixels can finish changing, the trailing edge of the object leaves a faint copy of itself behind. That smear is ghosting, and it is the practical meaning of the response time figure on a monitor specification sheet.

The test moves a hard edged white block across a mid grey field. Watch the back edge of the block rather than the block itself. A clean panel shows a sharp edge. A slow panel shows a grey tail.

Ghosting, overshoot and the overdrive setting

Every monitor with a response time worth advertising has an overdrive setting, usually buried in the menu as Response Time, OD, TraceFree, Rampage Response or something equally invented. It pushes extra voltage at the pixels to make them switch faster. Too little and you get ghosting. Too much and you get overshoot, which is a bright halo or inverse ghost trailing the object instead of a dark one.

  • Run this test with the overdrive setting off and note what the trailing edge looks like.
  • Step it up one level at a time, rerunning the test at each level.
  • Stop at the highest setting that shows no bright halo. That is the correct setting for your panel.
  • The best setting often changes with refresh rate, so retest if you switch between 60hz and the panel maximum.

What a browser test can and cannot show

A browser draws one frame per refresh at best, so this test shows you the panel behaviour that a browser can reach, which is honest but limited. It will clearly show bad ghosting, obvious overshoot, and the difference between overdrive settings, which is what most people came for. It will not give you a millisecond figure, because measuring true pixel response needs a photodiode and an oscilloscope rather than a web page, and any site that gives you a number in milliseconds from a browser is guessing.

If the motion looks stuttery rather than smeary, that is a different problem: a frame rate mismatch, a background process stealing time, or a variable refresh setting fighting the browser. Ghosting is a blur behind a smooth object. Stutter is the object jumping.

Frequently asked questions

What causes ghosting on a monitor?

Liquid crystal takes time to change state. When an object moves faster than the pixels can finish switching, the trailing edge leaves a faint copy of itself behind. That is the practical meaning of the response time figure on a specification sheet.

What is the difference between ghosting and overshoot?

Ghosting is a dark smear trailing a moving object, caused by pixels switching too slowly. Overshoot is a bright halo trailing it, caused by the overdrive setting pushing too hard. Tuning overdrive means finding the highest setting that shows no halo.

What overdrive setting should I use?

Start with it off, run this test, and step it up one level at a time, retesting each time. Stop at the highest setting with no bright halo. The best setting often changes with refresh rate, so retest if you switch between 60Hz and the panel maximum.

Can this measure response time in milliseconds?

No, and any browser based tool claiming a millisecond figure is guessing. Real pixel response measurement needs a photodiode and an oscilloscope. This test shows you bad ghosting, obvious overshoot and the difference between overdrive settings, which is what the setting actually needs.