Screen Uniformity Test
Compare brightness and tint across the whole panel, zone by zone.
Compare each zone against the centre one. Patchiness on mid grey is clouding; a colour cast that differs corner to corner is tint uniformity, and both are normal in small amounts. 50% grey shows the most, and white exposes dirty-screen effect — the faint vertical bands that show up as smearing when the camera pans in sport.
Your test runs locally in your browser. No device data is uploaded.
How to use the uniformity test
Go fullscreen and start on 50% grey, which shows the most. Compare each zone of the grid against the centre one rather than trying to judge the panel as a whole, then step through the other shades. White is the one that exposes dirty screen effect, and the darker greys show clouding.
What you are looking for
Clouding is uneven patchiness across the panel, usually caused by uneven pressure in the assembly. Tint uniformity is a colour cast that differs between corners, so grey looks slightly warm in one place and cool in another. Both are normal in small amounts and are worse on larger panels.
Dirty screen effect is the faint vertical banding visible on white or light grey. It is a manufacturing variation rather than dirt, no amount of cleaning changes it, and it is most obvious during slow camera pans in sport.
How this differs from backlight bleed
Backlight bleed is light escaping around the edges of the panel and is judged on a black screen. Uniformity is about the whole surface, and grey shows it far better than black does. A panel can have perfect edges and still be visibly blotchy in the middle, which is why the two are separate checks.
The zone grid exists because comparing a corner against the centre from memory is unreliable. A fixed reference lets your eye compare zones against each other instead of against an impression.
Frequently asked questions
- How is this different from the backlight bleed test?
- Backlight bleed is light escaping at the edges, judged on a black screen. Uniformity is about the whole panel: whether the middle is as bright as the corners, and whether grey stays grey everywhere. Grey fields show that far better than black, which is why this test uses them and adds a zone grid to compare against.
- What is the zone grid for?
- Comparing a corner against the centre from memory is unreliable. A visible grid gives your eye a fixed reference so you can judge zones against each other rather than against an impression.
- How much unevenness is normal?
- Some is normal on every LCD, and larger panels are usually worse. It matters when you can see it in ordinary use, particularly on flat backgrounds like a document or a video call. OLED panels are far more uniform but can show their own faint vertical banding.
- What is dirty screen effect?
- Faint vertical bands that become obvious during slow camera pans, most visible on white or light grey. It is a uniformity problem rather than dirt, and no amount of cleaning changes it.