How to run the color and uniformity test
- Set up first. Browser zoom at 100%, night light or True Tone off, brightness at your normal level. Sit where you usually sit.
- Press Start. Tap, click, or use the arrow keys to step through 14 screens. Esc exits.
- Solid colors: look for dots, darker corners and tints. A dot that’s wrong on one color is a pixel question, so open the dead pixel test.
- Gray steps and RGB gradients: the ramps should fade smoothly. The 32 steps should all look different from their neighbors.
- Uniformity: one flat gray. Press + or − (or the buttons) to change the level in 5% steps, and G for a 10 × 10 grid to note where a patch sits.
- Gamma, black level and white level: step back from the screen, then answer “What did you see?”
What each screen checks
| Screen | What to look for | What it usually means |
|---|---|---|
| Solid colors | Dots, tinted edges, darker corners | Pixel defects, uneven backlight |
| Gray steps | Hard bands, lines, merged steps | Limited color depth or heavy processing |
| RGB gradients | Bands, a color cast in the gray bar | Banding, a tint in the white point |
| Uniformity grid | Darker or tinted areas on flat gray | Panel uniformity, which varies from unit to unit |
| Gamma check | Which square blends into its stripes | Roughly how mid-tones are being shown |
| Black and white level | Squares you can’t see | Crushed shadows or clipped highlights |
The gray level shown on the uniformity screen is an RGB code value (50% is RGB 128). It isn’t a brightness measurement. Two screens showing “50%” can put out very different amounts of light.
How the gamma check works
Each column is made of alternating black and white lines, one device pixel each. Averaged by your eye, that’s half the screen’s maximum light. The solid square in the middle is the gray that should give the same light at gamma 1.8, 2.0, 2.2 or 2.4. The one that disappears into its stripes, when you squint, is roughly your screen’s gamma at mid-gray.
Most computer content assumes sRGB, which Lagom’s gamma test page describes as very close to gamma 2.2. Lagom also points out that few monitors hold one gamma across every brightness level, so treat this as a rough read. If the stripes look blurry or show a moiré pattern, your zoom or display scaling isn’t at a whole number and the check won’t be reliable.
Why gradients show banding
A smooth ramp from black to white needs every step to look a little different. When the computer runs at reduced color depth, Lagom’s gradient test notes you’ll see about 32 clear bands, and that’s a setting, not your monitor. Banding mostly in the dark ramp, or fine moving noise there, is more often the panel itself. Picture modes that boost contrast or “enhance” color can add bands too, so try a standard or sRGB mode before you judge.
What this test can’t do
It can’t calibrate your screen. A web page only sends color numbers. It can’t see the light coming out of the panel, and your operating system’s color profile and the monitor’s picture settings change what you see. Real calibration needs a colorimeter and software that writes a color profile for your display. Lagom recommends a hardware calibrator for photo work for the same reason.
So use this page to spot problems: banding, patches, tints, crushed blacks. For numbers like Delta E or brightness uniformity in percent, look for a review lab that measured your model, such as RTINGS’ gray uniformity test.
Frequently asked questions
Can a website calibrate my monitor?
No. A browser can show test patterns, but it can’t measure the light your screen puts out. Calibration needs a colorimeter and software that creates a color profile. This test helps you spot banding, patches and gamma that looks off, and fix what the monitor menu can fix.
What gray level should I use for a uniformity check?
The test starts at 50% gray, which shows darker corners and tints well. Then try 5% to 10% in a dim room for clouding in dark scenes, and 75% or higher for smudgy patches. The percentage is an RGB code level, not measured brightness.
Why do I see bands in the gradient?
Usually reduced color depth, a picture mode that adds processing, or a panel that struggles with dark tones. Lagom notes that a computer set to 16-bit color shows about 32 clear bands. Check your display settings for 8-bit or higher color first.
What does the gamma check result mean?
The square that blends into its striped surround is roughly your screen’s gamma at mid-gray. Most content assumes sRGB, which is very close to gamma 2.2. It’s a rough visual check that needs 100% zoom, and it can be thrown off by display scaling.
Is uneven gray a reason to return a monitor?
A little unevenness is normal on LCDs, and it varies between units of the same model. If you notice patches or a tint in normal use on a new screen, use the return window. Photos exaggerate it, so judge with your eyes at your usual brightness.
Sources
- Lagom LCD test: Gamma calibration, checked 2026-10-17.
- Lagom LCD test: Gradient (banding), checked 2026-10-17.
- RTINGS: Gray uniformity test, checked 2026-10-17.
- Wikipedia: sRGB, checked 2026-10-17.