NEW TO THIS? HERE’S THE PLAIN-ENGLISH VERSION.
What this test is
A solid white screen that shows how much light your monitor actually puts out, and how even that light is across the panel.
How it helps you
It helps you set a comfortable brightness for your room — easing eye strain — and check whether an “HDR 1000-nit” claim really holds up.
What we’re checking
Your panel’s real peak white output, whether it dims on full-white screens, and whether the centre is brighter than the corners.
Black level test - You should barely see the differences
Look for any light bleeding or gray tint in the black areas. True black should show no light emission.
F11 or Full Screen · ← → patterns · Esc exit
What Monitor Brightness Is
Brightness is measured in nits (cd/m²) — the panel’s maximum light output. A typical office monitor peaks at 250–350 nits; HDR-marketed panels reach 400–600 nits sustained; OLED and mini-LED can hit 1,000–2,000 nits on small highlights. The right level depends entirely on your room:
Approximate nit levels and where they fit.
How to Use the Test
- 1Go fullscreen. Press Full Screen, then display the solid white full-field pattern — the most demanding state for the backlight.
- 2Judge peak white. On 100% white, note whether the panel looks strong and clean or dims after a moment (APL limiting).
- 3Check uniformity. Compare the white level at the centre versus the corners. A big difference is a uniformity issue, not a brightness one.
- 4Set your working level. Drop to your normal brightness (not maximum) and confirm white still looks clean — not clipped or tinted.
Recommended Brightness by Use Case
| Environment | Recommended brightness |
|---|---|
| Dark room (evening) | 80–150 nits |
| Standard office, indirect light | 200–300 nits |
| Bright office, near a window | 300–400 nits |
| Sunlit / outdoor-facing workspace | 400+ nits |
| HDR highlight peaks (HDR content only) | 600–1000+ nits |
APL Dimming — Why “1000 Nits” Isn’t Always 1000
Many OLED and mini-LED monitors use ABL/ASBL (Automatic Brightness Limiter). When a large share of the screen is bright — high Average Picture Level — the panel lowers peak brightness to limit power draw and heat.
So a monitor advertised at 1,000 nits may only sustain 300–400 nits on a full white screen, with the peak reserved for small highlights. When comparing panels, look for “sustained” or “full-field” brightness, not just “peak”. This test’s full-white pattern is exactly the worst case that triggers APL limiting.
If white looks uneven rather than dim, that is a uniformity issue instead — check the uniformity test. And to judge how bright whites look against true black, pair this with the contrast test.
Brightness FAQ
How bright should my monitor be?+–
Match brightness to your ambient light. A simple guide: the white on your monitor should look about as bright as a sheet of white paper in the same lighting. Most people are comfortable at 150–250 nits indoors, higher near a window.
Can high brightness damage my eyes?+–
Running at maximum brightness in a dim room is tiring and can cause eye strain, but it does not cause permanent eye damage. Sustained discomfort is a signal to lower brightness and improve your ambient lighting rather than a sign of harm.
Does brightness affect monitor lifespan?+–
On OLED, yes — sustained high brightness accelerates organic pixel wear and raises burn-in risk, so keep OLED below roughly 80% for long sessions. On LCD with an LED backlight, high brightness causes minimal long-term degradation.
What is the difference between nits and lumens?+–
Nits (cd/m²) measure surface brightness — the correct unit for displays. Lumens measure total light output and apply to projectors and bulbs, not monitor panels. If a monitor is rated in lumens, treat the spec with suspicion.
Why is my 1000-nit monitor only showing 400 on white?+–
That is APL/ABL dimming working as designed. When a large area of the screen is bright, OLED and mini-LED panels reduce output to limit power and heat, so the 1,000-nit rating only applies to small highlights. Compare “sustained” or “full-field” brightness, not just “peak”, when shopping.
Is a brightness difference across the screen a defect?+–
A slight drop toward the corners visible only on full-field white is normal uniformity variation. A large, obvious difference — or coloured tinting across a big area — is a uniformity problem worth checking with the uniformity test and potentially returning.
Should I use auto-brightness?+–
Ambient-light auto-brightness is convenient and keeps the screen comfortable as room light changes, but it can interfere with colour-critical work by shifting your reference. For editing, set a fixed brightness matched to a controlled room; for general use, auto-brightness is fine.
Related Monitor Tests
Checking a whole new panel?
Run the dead pixel test and browse the full monitor test suite.