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 whether you saw one. That is all the page records: a browser cannot tell an OLED from fine zones from no zones, so it does not try.
This check is visual: it draws full-screen colours and test patterns on the screen, and you judge the result by eye, so a screen reader cannot describe it. The list under "What it measures" says in words what each one shows.
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.
In short
Local dimming test: the answer first
A local dimming test drifts small white shapes across black so you can see whether a halo follows them. A halo suggests the backlight dims in zones larger than the detail; no halo looks the same on an OLED, a fine zone panel and a panel with no zones, and the page does not guess which.
Reading your result
- Neither result is a fault
- The record is halo seen or no halo seen, in this room's light. It describes the panel, it does not fail it.
- A wide halo
- Lower the local dimming setting a step. The halo softens and the black lifts a little; many people keep it off for text and on for films.
- Grey black in a dark room
- Lower the brightness, and see the black level test for the panel's range.
What it measures
Measured here, not assumed.
- Halo seen
- A glow that moves with the shapes. It suggests the backlight is dimmed in zones larger than the detail; the fewer the zones, the wider the halo.
- No halo seen
- What an OLED, dimming zones fine enough not to show, and a backlit panel with no zones at all look like on this pattern. The page cannot tell them apart and does not name one.
- The record
- Halo seen or no halo seen, in this room's light. Neither is a fault.
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.
- No halo seen
- Nothing to change. If the black looks grey in a dark room, lower the brightness; the black level test says more about the panel's range.
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, measure black, or tell what the panel is; it shows the pattern that makes a halo visible.
- A halo is not a fault; it is how zone dimming works. The test tells you whether one shows 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, or tell whether the panel has any; it shows whether a halo is visible. Manufacturer pages list the count, from a few dozen to a few thousand.
- Does a halo mean my monitor is broken?
- No. It is how zoned backlights work. Fewer zones make a wider halo.
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