What is the uniformity test?
A uniformity test fills the screen with graduated grey levels so uneven backlighting, clouding and colour tint across the panel become visible.
Different uniformity faults show against different fields, which is why this test steps through the whole range rather than showing one grey. Backlight bleed and clouding are <a href="/black-screen">black-field</a> faults: they only appear as light escaping into what should be dark. The dirty screen effect and colour tint are <a href="/gray-screen">mid-grey</a> faults, invisible at both extremes and obvious in the middle.
How do you use the uniformity test?
Turn the room lights off, go fullscreen, and step through the grey levels watching the corners and edges for lighter patches.
- Turn the room lights off and go fullscreen — bleed is invisible in a lit room.
- Step through the grey levels and watch the edges and corners for lighter patches.
- Compare the left and right halves of the screen for a colour shift.
What is backlight bleed?
Light escaping around the edges of an LCD panel, visible as brighter patches in the corners on dark content. It is a matter of degree.
An LCD is lit from behind and shows black by blocking that light, which it can never do perfectly. Some bleed is normal on every LCD; the question is whether yours is bad enough to distract you during dark scenes.
What is the difference between clouding and the dirty screen effect?
Clouding is patchy brightness on a black field. The dirty screen effect is fine blotching on mid grey. They are separate faults with separate tests.
They get used interchangeably and should not be. RTINGS measures them on different patterns: clouding and flashlighting on a black field, and the dirty screen effect on grey. Practically, the dirty screen effect is what you notice during slow camera pans across something uniform like a football pitch — which is why people usually spot it watching sport rather than working.
Does OLED suffer from backlight bleed?
No. OLED lights each pixel individually with no backlight to leak, so bleed and clouding cannot occur at all on those panels.
OLED has its own uniformity characteristic instead: faint horizontal and vertical banding, most visible on very dark greys rather than mid tones. It is noticeably better on recent panels than on older ones. Run the dead pixel test alongside this for a full check.
Why do I need the room dark to check uniformity?
Because ambient light reflecting off the screen masks the very differences you are looking for, which are small and low-contrast.
A bright room can hide bleed completely and make a bad panel look fine.
Does this cost anything or need an account?
No. Every tool here is free, needs no sign-up, and runs in the browser with nothing to install and nothing stored.
There are no accounts, no paywalled sizes and no watermarks on downloads. See the full list of screen tools.
Will my screen stay awake while it runs?
Yes, with Keep awake switched on. It holds a browser wake lock so the display stays lit with no input until you leave.
Useful when a screensaver or clock is meant to run unattended. The lock is released as soon as you close the page.
Put this on your site
The embeddable version drops the page around it and runs the tool on its own.