Screen Uniformity Test
Display uniform gray screens to detect dirty screen effect (DSE), mura, and uneven backlighting.
What to look for
- Dirty screen effect: Splotchy, cloudy areas visible on uniform gray.
- Mura: Panel-level non-uniformity caused by manufacturing.
- Most visible at 5-25% gray levels.
Testing guide
How to test screen uniformity
Uniformity is how evenly a panel lights across its whole surface. Full-field gray and solid colors expose clouding, dirty screen effect, backlight hotspots, and tint shifts that are invisible in ordinary content but obvious once you know how to look.
Best for
- Checking a new panel for clouding or blotchy backlighting inside the return window.
- Diagnosing the dirty screen effect that shows up as grubby patches during panning shots and sports.
- Comparing edge-to-center brightness falloff between two displays.
How to run the test
- 1Run the test in a dark room, since uniformity problems are far harder to see in ambient light.
- 2Display a mid-gray full field first, which reveals the dirty screen effect better than any other shade.
- 3Move on to full black to check for backlight bleed and clouding around the edges and corners.
- 4Finish with solid white to check for tint shifts and brightness falloff toward the edges.
How to read the result
Blotchy vertical or horizontal smudges on mid-gray are the dirty screen effect, common on large VA and IPS panels.
Bright patches leaking inward from the edges on black are backlight bleed; broad cloudy areas are clouding.
A warmer or cooler tint toward one side on a white field indicates uneven color temperature across the panel.
Related tools and guides
Frequently asked questions
What is the dirty screen effect?
Dirty screen effect, often shortened to DSE, is uneven brightness across the panel that looks like faint smudges or streaks. It is most visible on mid-gray full fields and during slow camera pans, such as sports footage across a playing field.
Is some screen unevenness normal?
Yes. Essentially every LCD has some uniformity variation, and larger panels tend to have more. It only matters if it is visible in the content you actually watch, or if it is severe enough to meet the manufacturer replacement threshold.
What is the difference between clouding and backlight bleed?
Backlight bleed is light escaping around the edges of the panel, appearing as bright patches creeping in from the borders. Clouding is broader, softer unevenness spread across the middle of the screen. Both come from the backlight rather than the pixel layer.
Can uniformity problems be fixed?
Not by software. Some monitors offer a uniformity compensation mode, which evens out brightness at the cost of peak brightness and contrast. Otherwise it is a physical property of the panel and backlight assembly, so a return or exchange is the only real remedy.
Why does my screen look uneven only in dark scenes?
Backlight problems are masked by bright content but obvious against dark backgrounds, where any leaked or uneven light has high relative contrast. This is why uniformity testing should always be done in a dark room.
Testing guide
How to test screen uniformity
Uniformity is how evenly a panel lights across its whole surface. Full-field gray and solid colors expose clouding, dirty screen effect, backlight hotspots, and tint shifts that are invisible in ordinary content but obvious once you know how to look.
Best for
- Checking a new panel for clouding or blotchy backlighting inside the return window.
- Diagnosing the dirty screen effect that shows up as grubby patches during panning shots and sports.
- Comparing edge-to-center brightness falloff between two displays.
How to run the test
- 1Run the test in a dark room, since uniformity problems are far harder to see in ambient light.
- 2Display a mid-gray full field first, which reveals the dirty screen effect better than any other shade.
- 3Move on to full black to check for backlight bleed and clouding around the edges and corners.
- 4Finish with solid white to check for tint shifts and brightness falloff toward the edges.
How to read the result
Blotchy vertical or horizontal smudges on mid-gray are the dirty screen effect, common on large VA and IPS panels.
Bright patches leaking inward from the edges on black are backlight bleed; broad cloudy areas are clouding.
A warmer or cooler tint toward one side on a white field indicates uneven color temperature across the panel.
Related tools and guides
Frequently asked questions
What is the dirty screen effect?
Dirty screen effect, often shortened to DSE, is uneven brightness across the panel that looks like faint smudges or streaks. It is most visible on mid-gray full fields and during slow camera pans, such as sports footage across a playing field.
Is some screen unevenness normal?
Yes. Essentially every LCD has some uniformity variation, and larger panels tend to have more. It only matters if it is visible in the content you actually watch, or if it is severe enough to meet the manufacturer replacement threshold.
What is the difference between clouding and backlight bleed?
Backlight bleed is light escaping around the edges of the panel, appearing as bright patches creeping in from the borders. Clouding is broader, softer unevenness spread across the middle of the screen. Both come from the backlight rather than the pixel layer.
Can uniformity problems be fixed?
Not by software. Some monitors offer a uniformity compensation mode, which evens out brightness at the cost of peak brightness and contrast. Otherwise it is a physical property of the panel and backlight assembly, so a return or exchange is the only real remedy.
Why does my screen look uneven only in dark scenes?
Backlight problems are masked by bright content but obvious against dark backgrounds, where any leaked or uneven light has high relative contrast. This is why uniformity testing should always be done in a dark room.