Screen Uniformity Test: Monitor Brightness Uniformity Test
Screen Uniformity Test. Click Start Brightness Test to run this monitor brightness uniformity test and spot dim corners and uneven patches. The free screen uniformity test is free and runs entirely client-side, so nothing about your display is ever uploaded.
Interactive Tool
This monitor brightness uniformity test fills your screen with a full white field and a 50% gray field so you can judge peak output and spot dim corners or patchy backlight brightness with your own eyes. Click Start Brightness Test, watch for a few seconds to catch OLED panels dimming under automatic brightness limiting, and scan corner-to-corner for unevenness — your browser can't read actual nits, so treat this as a visual check, not an instrument reading.
A dim corner or a cloudy patch is easy to miss on a busy desktop, yet it can quietly skew every photo you edit. This free monitor brightness uniformity test fills your display with solid grayscale levels and colours so you can see whether the panel stays consistent from edge to edge, or whether backlight uniformity is failing in an uneven, gradual way. Think of it as a quick online screen uniformity test that catches pixel degradation early, on a desktop monitor, laptop, smartphones or tablets alike, before a small gray test flaw turns into a big one.
What a Monitor Brightness Uniformity Test Measures
Brightness uniformity describes how evenly a screen reproduces the same signal across its whole surface. A perfect panel would show a flat field with zero variation between the center, the edges and the corners. Real panels never do. This uniformity test is a visual test, so results are partly subjective: it shows you where the light falls off, while a measurement tells you by how much. Both are hardware faults in the end, which is why no software setting fully removes them.
Brightness Deviation and the Nine-Point Grid
Reviewers turn the visual impression into a number by reading luminance at a nine-point grid (a 3x3 grid) with a colorimeter, then comparing each zone with the center:
$$\text{Deviation}\,(\%) = \frac{L_{\text{centre}} - L_{\text{zone}}}{L_{\text{centre}}} \times 100$$Take a 27-inch office panel read at a fixed setting, with the centre at 164.8 nits:
| Zone | Left | Centre | Right |
|---|---|---|---|
| Top | 141.2 nits (14.3%) | 152.6 nits (7.4%) | 147.9 nits (10.3%) |
| Middle | 155.3 nits (5.8%) | 164.8 nits (0%) | 158.1 nits (4.1%) |
| Bottom | 138.5 nits (16.0%) | 149.7 nits (9.2%) | 144.0 nits (12.6%) |
The worst brightness deviation is 16.0% in the bottom-left corner, against a common guideline that under 10% is excellent for color-critical work. Labs also quote luminance deviation as a standard deviation (8.0 nits here) and add chromaticity readings; a 5-by-5 grid simply maps the falloff in finer detail.
Where Uniformity Issues Show Up in Games and Video
Uniformity issues hide in busy scenes and appear in smooth ones: a pale sky, open ocean, fog, snow, sports fields and slow camera pans. Open-world games and flight games fill the display with exactly that kind of content. In gaming, dark scenes on an ultrawide panel reveal more than any refresh rate figure, because a patch that stays fixed while the image moves breaks immersion; if it moves with the sky, the games themselves are the cause. Video, movies, photography, design work and editing photos all suffer the same way, so treat image quality and even skies as one buying criterion.
Choosing the Right Gray Test Patterns
Not every pattern exposes every flaw, so a good gray test cycles several test patterns rather than one. Mid-gray is the workhorse: a solid gray field is bright enough to show patches but dim enough that subtle gray uniformity errors are not washed out. Start with the gray screen, then step through the grayscale levels; once the gray patterns look clean, move to colours. That order makes uniformity testing faster, because each test pattern answers one question. Run the monitor viewing angle test tool to check your display for this issue directly in your browser — no download required.
50% Gray, 25% Gray and 5% Gray for Dirty Screen Effect
The dirty screen effect (DSE) looks like a smudged window over the image. Open 50% gray first and scan slowly. If anything looks off, drop to 25% gray, which many testers treat as the standard DSE pattern, and then to 5% gray. The darkest levels catch near-black faults that brighter fields hide, which matters most on OLED panels.
Black, White, RGB and Gradient Screens
- A white screen shows tint, dust and edge falloff.
- A black screen shows glow, leakage and bright stuck pixels.
- Solid colors in RGB (red, green, and blue) reveal whether one channel is uneven, and help find dead pixels and other pixel defects.
- Gradients reveal stepping: a smooth horizontal or vertical gradient should never jump between tones, and no single pixel should stand out.
How to Run a Screen Uniformity Check Step by Step
A full screen uniformity check takes about ten minutes and needs nothing beyond this page and your own eyes:
- Let the monitor run for a while at the brightness you normally use.
- Open the tool and switch to fullscreen with the button or F11, so no taskbar or browser bar breaks the field.
- Sit at your normal viewing position, then lean back slightly to take in the whole panel.
- Step through gray, white, black and colour patterns, scanning the center, edges and corners each time.
- Write down which pattern shows each flaw and where it sits on the screen.
Judge with your eyes, not a phone photo: cameras exaggerate some faults and hide others. If a problem appears in everyday use, keep your notes in case you need to return the unit. The tool runs the same screen uniformity test on any browser.
Settings to Disable Before You Test Uniformity
Turn off dynamic contrast, eco dimming and auto brightness, since each one changes output while you look. Pick the picture mode you actually use and leave gamma at its default. Then let the panel warm up for 15 to 30 minutes, because a cold backlight is often less even than a warm one.
Dark Room, Viewing Angle and Viewing Distance
A dark room or a dimly lit one makes faint patches easier to see, and it removes reflections on the display that look like faults. Keep room lighting steady between tests. Move your head a little: if a patch shifts with your viewing angle it is glow, not a panel fault. Hold the same viewing distance each time.
Proofing a New 32-Inch IPS Monitor's Panel Uniformity at 120 Nits
I retouch product shots for print, and a new 32-inch IPS monitor has just arrived with a 30-day return window. The decision is simple: keep it, or ask for an exchange while I still can. The answer came out as exchange: the bottom-left corner sits 14.2% below the centre, past the 10% line colour-critical reviews treat as excellent.
I start visually. After a 30-minute warm-up at my working calibration target of 120 nits, with dynamic contrast off, I run the 25% gray pattern in fullscreen from my chair. The lower-left looks faintly dull, nothing more. A faint impression is not a reason to send a monitor back, so I measure.
With a colorimeter on a 3x3 grid, the centre reads 118.6 nits. The corners read 104.9 (top left), 109.3 (top right), 101.7 (bottom left) and 106.2 (bottom right). I enter each reading against the centre:
- Bottom left: (118.6 − 101.7) ÷ 118.6 = 14.2%
- Top left: 11.6%; bottom right: 10.5%; top right: 7.8%
- Edge midpoints: 3.0% to 6.6%
I recheck the worst one by hand: 16.9 divided by 118.6 is 0.142. Three corners fail the brightness deviation guideline, and the dull patch I saw on gray is the worst of them.
Then a sensitivity rerun at the panel's 250-nit preset:
| Setting | Centre | Bottom left | Deviation |
|---|---|---|---|
| Proofing, 120 nits | 118.6 | 101.7 | 14.2% |
| Preset, 250 nits | 247.3 | 219.8 | 11.1% |
The falloff is proportionally worse at the dim setting I actually use, which is why I test at my working brightness, never at the shop preset. The second caveat is the reference point: measured against the nine-zone average of 110.2 nits instead of the centre, the worst zone is only 7.7% off and the panel "passes". Centre-referenced deviation is the convention, so I quote that, and I'd distrust any spec sheet that doesn't say which one it used.
My judgement: for web work this uniformity test result would be fine. For print proofs, where a vignette in the lower-left can push me to over-brighten a corner, it is not. I file the exchange on day four and plan to rerun the same 120-nit grid on the replacement.
Spotting Uniformity Problems: Backlight Bleed, DSE and Clouding
Most uniformity problems fall into a few families. Backlight bleed, DSE and clouding look alike at first, so this backlight check sorts the uneven areas by pattern and location. Rate the unevenness by whether you notice it in real content, not only on a test field.
Clouding, Hotspots and Mottled Gray Areas
Clouding shows as cloudy patches on dark fields, often from uneven pressure on the panel. Brightness hotspots near the middle are typical of edge-lit designs, while dark patches can point to panel damage. A mottled or blotchy look on mid-gray is the DSE signature, and you will notice it most during slow pans.
IPS Glow, Corner Glow and Black Uniformity
On a black field, light leaking from the frame is backlight bleed, also called edge leakage. IPS glow is different: a silvery corner glow that changes as you move. Black uniformity covers both, plus dim corners and edge darkening on bright fields. Poor black levels from a stray backlight also lower usable contrast in dark content.
Color Tint, Banding and Burn-In
Color tint appears as one side looking warmer and more yellow, the other cooler and more blue, a shift in color temperature that hurts color accuracy. Tint shifts are clearest on white and light gray. Banding shows as vertical bands, vertical banding or vertical streaks, common on OLED near black. Burn-in and image retention leave ghost shapes from static content.
Display Uniformity by Panel Type: OLED, LCD and Mini LED
Display technology decides which faults you are likely to find, so the panel type tells you which patterns to run longest. LCD panels rely on a backlight, while OLED pixels are self-lit and have none to leak.
| Panel | Typical uniformity risk | Patterns to watch |
|---|---|---|
| VA panels | Most prone to DSE | 25% and 50% gray |
| IPS panels | Glow and bleed in the corners | Black in a dim room |
| TN panels | Shift with viewing position | Gray from your seat |
| Mini LED | Local dimming zones and blooming | Black with a bright object |
| OLED | Near-black streaks, tint, burn-in | 5% and 10% gray |
Review measurements of black-uniformity deviation consistently favour OLED, which suits dark gaming setups, yet any single IPS, VA or TN unit can beat the average. The same applies to QLED and HDR TV sets used as a gaming display: a larger screen size exposes more of the edges, while a laptop sits so close that small differences look bigger.
Color Uniformity, Calibration Limits and When to Return a Monitor
Calibration fixes gamma, grayscale balance and overall colour, but it cannot make a dim corner match the centre or repair poor color uniformity. Some premium models offer hardware uniformity compensation, which evens out monitor uniformity at the cost of some peak output. Minor variation is normal on any LCD. Treat it as a defect when it shows in daily use or in the games you play, and ask the manufacturer for an exchange under warranty if a defective panel is still covered. Good panel uniformity should look even on the patterns you use most.
Second-Hand Screens and the Return Window
Buying a second-hand gaming or office monitor? Ask the seller to open this page on it, then step through a gray screen and a black screen before you pay. If a corner looks clearly dimmer than the center or light bleeds from the frame, walk away: what this check shows is the uniformity you would live with. For a new unit, run every pattern on day one so you can act well inside the retailer's return window.
Frequently Asked Questions
- Why is gray the best pattern for a brightness uniformity test?
- Mid-gray is bright enough to show darker corners and cloudy patches but not so bright that subtle differences wash out. Pure black hides most brightness falloff, and white can be too bright to see gentle variation. Start at 50% gray, then 25% and 5%.
- How many gray levels should I check?
- Gray 50%, 25% and 5% catch most problems. If you have time, step through all 21 levels from 0% to 100% in 5% steps: near-black levels reveal OLED banding and tint, mid levels reveal dirty screen effect, and light levels reveal colour tint.
- Is poor uniformity the same as backlight bleed?
- No. Poor uniformity is any uneven brightness, black level or tint across the panel. Backlight bleed is one specific LCD fault: light leaking from the frame, seen on black in a dark room. A monitor can look even on gray and still bleed at the edges.
- Can uniformity problems be fixed with software or calibration?
- Mostly not. Calibration corrects gamma and colour balance, but it cannot make a physically dim corner match the center. Some premium monitors have hardware uniformity compensation; otherwise a severe case is a reason to exchange the unit.
- How much variation is normal?
- Every LCD panel shows some variation, especially toward the corners of large screens. If you only see it on test patterns, it is usually normal. If it shows in games, video or everyday work, treat it as a defect and act within the return window.
- Does this test work on OLED and LCD screens?
- Yes. On LCD, IPS, VA and Mini LED panels look for backlight bleed, IPS glow, clouding and dirty screen effect. On OLED there is no backlight to leak, so focus on near-black gray levels for banding, tint and burn-in.
- How do I get accurate results?
- Go fullscreen, turn off dynamic contrast and auto brightness, let the monitor warm up, dim the room and sit at your normal viewing position. Judge with your eyes rather than a phone photo, since cameras exaggerate or hide unevenness.