Blooming Test
Detect blooming and halo artifacts on mini-LED and local dimming displays. Small bright objects on black backgrounds reveal the tradeoff of zone-based dimming.
Why use this hdr tool
Multiple bright shapes
Squares, circles, and dots of various sizes let you measure blooming at different brightness levels.
Zone count estimation
Move the bright object and count visible halos to estimate your display's effective dimming zone count.
Brightness ramp
Test at 25%, 50%, 75%, and 100% white to see how blooming scales with object brightness.
Position grid
Place bright objects at center, edges, and corners to map blooming uniformity across the panel.
What is hdr
Blooming is the halo of light surrounding a bright object on a dark background, caused by local dimming zones that are too large to isolate small bright objects. Mini-LED displays with hundreds or thousands of dimming zones have less blooming; edge-lit displays with a handful of zones have severe blooming.
Local dimming works by dividing the backlight into zones that can be dimmed or brightened independently. When a zone contains a bright object, the display brightens that zone's LEDs. But the entire zone brightens, not just the bright object — so the area around the object also gets brighter, creating a visible halo. The smaller the zones, the smaller the halo.
OLED has no blooming because each pixel is its own light source — there are no zones to leak light. Mini-LED displays with 1000+ zones approach OLED-like blooming performance but still show halos around the brightest small objects. Edge-lit displays with a dozen zones show blooming so severe that local dimming is often worse than off.
How to test
Step 1: Display a bright dot on black
Open the test and select a small bright object. The display shows a white dot on a pure black background.
Step 2: Look for halos
A perfectly black surround with a sharp white dot indicates no blooming. Any glow around the dot is blooming.
Step 3: Move the object
Drag the bright object to different positions. Count distinct halos to estimate your display's zone count.
Step 4: Test multiple shapes
Switch between square, circle, and dot. Smaller objects reveal blooming more clearly than large ones.
Step 5: Adjust local dimming
Open the monitor's OSD and toggle local dimming High/Medium/Low/Off. Re-test to see how blooming changes.
Common causes of hdr issues
Large dimming zones
Edge-lit displays have 4-8 zones; the entire edge brightens for any bright object, producing huge halos.
Insufficient zone count
Mini-LED with 100-500 zones still shows visible blooming around small bright objects. 1000+ zones is needed for minimal blooming.
Over-aggressive dimming
High local dimming setting brightens zones maximally, increasing halo size. Medium often looks better.
Zone bleed
Light from a bright zone leaks into adjacent dimmed zones, expanding the halo beyond the zone boundary.
Frequently asked questions
Testing tips
- Test in a dark room — blooming is more visible without ambient light.
- Use small bright objects (dots, not large squares) to maximize blooming visibility.
- Compare local dimming High, Medium, and Off — sometimes Medium looks best.
- Count visible halos when moving the object to estimate your display's zone count.
Related tools
Mini LED Blooming: Why More Dimming Zones Matter
You bought a mini-LED monitor with 500 dimming zones, expecting OLED-like contrast. Then you noticed it: a faint halo around your white cursor on a black desktop, around bright stars in a night sky, around subtitles during dark movie scenes. That's blooming — the tradeoff of zone-based local dimming. Understanding blooming explains why mini-LED displays range from mediocre to OLED-killer, all based on one number: zone count.
Local dimming divides the backlight into independent zones that can be dimmed or brightened. When a zone contains a bright object, that zone's LEDs brighten. But the entire zone brightens, not just the bright object — so the area around the object also gets brighter, creating a visible halo. The smaller the zones, the smaller the halo. Edge-lit displays with 4-8 zones have huge halos; mini-LED with 1000+ zones have halos only around the smallest, brightest objects.
Test your display with our blooming test. Display a small white dot on a black background — any glow around the dot is blooming. Move the dot around the screen and count distinct halos to estimate your display's effective zone count. A 500-zone display shows about 500 distinct halo positions; an edge-lit display shows 4-8 huge halos. OLED shows zero halos because each pixel is its own light source.
The tradeoff is unavoidable on mini-LED. More zones means smaller halos but also more expensive backlight hardware. Premium mini-LED TVs like the Samsung Neo QLED have 2000+ zones and show minimal blooming. Budget mini-LED monitors with 200-500 zones show obvious blooming around small bright objects. Edge-lit monitors with a handful of zones are essentially unusable for HDR — the blooming is more distracting than the elevated black level they're trying to fix.
Tune your local dimming setting. Most monitors offer High, Medium, and Low. High maximizes contrast but produces the largest halos. Medium is often the sweet spot — slightly elevated blacks but smaller, less distracting halos. Off eliminates blooming entirely but raises the black floor across the whole screen. Test each with the blooming test and pick what looks best for your typical content.
For HDR movies and games, mini-LED with 1000+ zones approaches OLED performance at lower cost and higher peak brightness. For dark-room movie watching with small bright objects (subtitles, stars, cursors), OLED remains the gold standard. Pair the blooming test with our contrast test and HDR test to evaluate the full local-dimming tradeoff. More zones matter — but only you can decide how many you need.
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