Local dimming test. Black, around the light.
A backlit screen with local dimming darkens the zones behind dark picture and lights the zones behind bright picture. When the zones are larger than the detail, a halo appears around bright things on black. Small white shapes drift on black here so a halo has somewhere to show; you say what you see.
One check
- Local dimming
One check after another, with your progress along the top and a plain verdict on each. Nothing you show the camera or say into the microphone leaves this page.
What it measures
Measured here, not assumed.
- A halo
- A glow that moves with the shapes: the backlight's zones are larger than the detail. The fewer the zones, the wider the halo.
- Black stays black
- An OLED, where each pixel is its own light, or dimming zones fine enough not to show.
- Grey black
- A backlit panel without local dimming, which is most monitors. The black is an even grey in a dark room.
If it fails
The usual failures, and what fixes each.
- A wide halo
- Lower the local dimming setting a step: the halo softens and the black lifts slightly. Or turn it off for text work and on for films.
- Grey black
- Nothing to change; the panel has no zones. Lower brightness in a dark room helps.
- Black stays black
- Nothing to change.
Where a browser stops
What it cannot tell you.
- Your eyes judge it, in a dim room; in daylight a halo is hard to see and the test says nothing about the panel.
- A page cannot count zones or measure black; it shows the pattern that makes the difference visible.
- A halo is not a fault; it is how zone dimming works. The test tells you which kind of screen you have and what softens it.
Privacy
Nothing leaves this page.
The camera and microphone are read on this page and stopped as soon as they have been measured. The clip you can play back lives in the browser's memory and is discarded when you leave. The location check discards the position. The internet test sends random bytes to this site and nothing else. The result is stored nowhere unless you ask for it by email, and then only the fact that an email was sent is kept.
Questions
Local dimming test, answered
- What is blooming on a monitor?
- A halo of light around bright objects on a dark background, from backlight dimming zones larger than the object. More zones mean smaller halos; an OLED has none.
- Is local dimming worth turning on?
- For films in a dark room, usually yes: deeper black and brighter highlights. For text and interfaces it can flicker and halo; many people turn it off for work.
- How many dimming zones does my screen have?
- This test cannot count them; it shows how visible their halo is. Manufacturer pages list the count, from a few dozen to a few thousand.
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