Brightness Test
Measure your display's peak and sustained brightness. Test patterns reveal whether your monitor delivers its advertised nits, and how brightness scales with content.
Why use this brightness tool
Peak brightness windows
1%, 10%, 25%, 50%, and 100% white windows reveal how brightness scales with content area on HDR displays.
Brightness ramp
Smooth ramp from black to white lets you visually compare brightness perception across the panel.
Uniformity grid
9-zone white fullscreen reveals brightness uniformity across the panel — corners are often dimmer than center.
ABL behavior test
Sustained large-area white reveals automatic brightness limiter (ABL) behavior on OLED and HDR displays.
What is brightness
Brightness is the luminance of your display, measured in nits (candela per square meter, cd/m²). Typical SDR monitors deliver 250-400 nits; HDR displays hit 600-2000 nits peak; HDR TVs can reach 3000+ nits. Higher brightness enables HDR highlights, daylight visibility, and perceived dynamic range.
Peak brightness depends on the size of the bright area. Most HDR displays hit their advertised peak only on small (1-10%) white windows — a 100% white fullscreen may be 40-60% of peak due to thermal and power limits. This is called ABL (automatic brightness limiter), and it's especially aggressive on OLED.
Brightness interacts with contrast and black level. An LCD's contrast ratio is roughly brightness divided by black level — so raising brightness raises black level proportionally, keeping contrast constant. OLED contrast is infinite (black is zero) regardless of brightness, so HDR OLED delivers both deep blacks and bright highlights.
How to test
Step 1: Display the 100% white window
Open the test and select 100% white. Note the perceived brightness — this is your display's sustained fullscreen brightness.
Step 2: Switch to 10% window
Display the 10% white window (a small bright square on black). Note the increase in brightness — this is your peak HDR brightness.
Step 3: Test 1% window
Display the 1% window. HDR displays hit their absolute peak here — spec highlights like sun glints and explosions.
Step 4: Run the uniformity grid
Display the 9-zone white fullscreen. Compare center brightness to corners — 10-20% variation is typical.
Step 5: Test ABL behavior
Switch between small and large white areas. If fullscreen brightness drops dramatically, ABL is engaging.
Common causes of brightness issues
Panel type limits
OLED peaks at 600-1000 nits for HDR but ABL limits fullscreen to 150-250 nits. Mini-LED hits 1500+ nits peak, 800+ fullscreen.
Thermal throttling
Sustained high brightness heats the backlight or pixels, triggering ABL to protect the panel. Brightness recovers after cooling.
Power supply limits
Laptops and portable monitors cap brightness to preserve battery or stay within USB-C power budgets.
Ambient light mismatch
A 400-nit display looks dim in direct sunlight. Phones often hit 1000+ nits for outdoor visibility; monitors rarely need this.
Frequently asked questions
Testing tips
- Compare 10% and 100% white windows to see your display's ABL behavior.
- Set brightness to 120-150 nits for SDR in a dim room — higher causes eye strain.
- Test uniformity with the 9-zone grid — corners are often 10-20% dimmer than center.
- For HDR, look for DisplayHDR 600 or 1000 — HDR400 is essentially SDR brightness.
Related tools
Monitor Brightness: How Many Nits Do You Really Need
When monitor shopping, brightness is one of the most-advertised specs: 350 nits, 600 nits, 1000 nits, even 2000 nits on premium HDR TVs. But what do these numbers mean, and how many do you actually need? The answer depends on your environment, your content, and whether you care about HDR — and the marketing numbers are often misleading.
Brightness is measured in nits (candela per square meter, cd/m²). Typical SDR monitors deliver 250-400 nits, which is plenty for indoor use. HDR displays hit 600-2000 nits peak, and premium HDR TVs reach 3000+ nits for specular highlights like sun glints and explosions. Higher brightness enables HDR's expanded dynamic range — without it, HDR looks no different from SDR.
Here's the catch: advertised peak brightness usually applies to small (1-10%) white windows, not fullscreen. A 1000-nit display may show only 600 nits on a 50% window and 400 nits on 100% white. This is ABL (automatic brightness limiter), which reduces brightness on large bright areas to protect the panel from thermal damage. OLEDs have aggressive ABL — a 100% white fullscreen may be 25% of the peak 10% window brightness. Mini-LED ABL is less aggressive. Test your display with our brightness test using different window sizes.
How many nits do you need? For indoor SDR use, 250-400 nits is plenty — your eyes will adapt to the room, and higher brightness just causes eye strain. For HDR, 600+ nits (DisplayHDR 600) is the minimum for visible improvement; 1000+ nits (DisplayHDR 1000) is ideal for true HDR specular highlights. For bright rooms with direct sunlight, look for 800-1000+ nits on monitors or 1500+ on TVs. For phones used outdoors, 1000+ nits is essential.
Beware the DisplayHDR 400 trap. This certification requires only 400 nits peak (similar to SDR), 8-bit color, and no local dimming. It accepts HDR signals but cannot render real HDR — the peak brightness is too low to differentiate HDR highlights from SDR content. Look for DisplayHDR 600 or 1000 for genuine HDR. OLED displays have their own certification path and deliver excellent HDR despite lower peak brightness because their infinite contrast compensates.
Set brightness based on your environment, not the spec sheet. For SDR in a dim room, 120-150 nits is comfortable; higher causes eye strain over time. For bright rooms, raise to 300-400 nits. For HDR content, leave the display at its default HDR brightness — the content is mastered for specific nit levels. Pair the brightness test with our contrast test and greyscale test for a complete picture of your display's performance.
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