Blooming & Halo Test.
Launch a shape full screen against pure black, then dim it with ↑/↓ — any grey glow that appears around it is blooming from your backlight's dimming zones.
How the blooming test works
An LED-backlit LCD can't switch off light behind a single pixel — it dims the backlight in zones, each covering many pixels. Show a small bright object on black and its zone has to stay lit, so the black pixels sharing that zone glow grey. That halo is blooming, and the fewer zones a panel has, the bigger it gets. A pure-black field with one bright shape is the cleanest way to see it.
- 1. Kill the lights. Bloom is a low-light artefact — in a bright room the backlight overwhelms it.
- 2. Start with the small dot and star. Tiny, sharp highlights on black stress the backlight most and show the clearest halo.
- 3. Ride the brightness. Use ↑/↓ to dim the shape and watch the halo shrink — it tells you how aggressive your panel's dimming is.
- 4. Compare against the panel table. Match what you see to your display's backlight type to judge whether the bloom is normal for its class.
Local dimming & bloom by panel type
How much bloom is "normal" depends entirely on how your backlight is built. More dimming zones means each bright object lights fewer black pixels around it.
| Dimming zones | Panel class | Expected bloom |
|---|---|---|
| Edge-lit / none | Basic LED | Whole-screen glow, obvious halos |
| < 32 | Entry FALD | Clear halos around bright objects |
| 128 – 512 | Mid FALD | Small halos, strong contrast |
| 512 – 2000 | High-end FALD | Minimal, only on tiny highlights |
| 2000+ / per-pixel | Mini-LED elite / OLED | Effectively none |
A little bloom on a zone-dimmed LCD is expected, not a fault. It only matters if it distracts you in real use — subtitles, letterbox bars, a cursor on a dark desktop. If any bloom at all bothers you, that's the case for an OLED or a per-pixel mini-LED panel.
What your results mean
Match what you saw on the shape and the ↑/↓ brightness control to what it says about your backlight, and whether it's worth changing anything.
| What you see | What it means | What to do |
|---|---|---|
| Black stays black around the small dot and star, even near 100% brightness | Your backlight has enough dimming zones (or is OLED / per-pixel mini-LED) to isolate a bright highlight from the black around it | Nothing to do — this is the result you want. |
| A soft, round glow rings the shape and shrinks as you dim it with ↓ | Normal blooming on a zone-dimmed LED LCD — the highlight's dimming zone can't go fully black while it's lit | Expected behaviour; check the panel table above to see if the halo size matches your backlight's zone count. |
| The glow has a hard, boxy edge instead of a soft round shape | You're seeing the actual edge of one dimming zone — a sign of a lower zone count | Set by the panel's zone count, not a menu option; only a higher-zone or per-pixel (mini-LED / OLED) panel removes it — a hardware limit. |
| The large circle blooms almost as much as the small dot | Bloom isn't shrinking with a bigger highlight, meaning the zones covering your screen are few and large | Matches the "Edge-lit" or "Entry FALD" rows above; nothing to adjust — it's the panel class. |
| A faint grey haze covers the whole black field, not just around the shape | That's backlight bleed — light leaking at the panel's edges even with nothing bright on screen — a different issue from blooming | Check it on its own with the black level test. |
Frequently asked questions
What is blooming on a monitor or TV?
Blooming (or haloing) is a faint glow of light spreading out from a bright object into the black area around it. It happens on LED-backlit LCDs because the backlight is shared across zones: to light a small highlight, the backlight also lights the black pixels nearby, so they glow grey instead of staying black. This test puts a bright shape on pure black so that halo is easy to see.
How do I test for blooming?
Dim the room, launch the test full screen and step through the shapes — especially the small dot and the star, whose fine points stress the backlight most. Look for a soft grey glow or a boxy patch of light around the white shape. Use the ↑/↓ brightness control to see how bright the object has to be before the halo appears. Move the shape mentally around the screen by trying different modes; corners and edges often bloom differently from the centre.
Why does my screen glow around bright objects on black?
Because your panel is LED-backlit with a limited number of dimming zones. Each zone can only be one brightness, so a bright subtitle or star on black forces its whole zone brighter, and the black in that zone glows. Fewer zones (or none, on edge-lit panels) means bigger, more obvious halos. OLED and per-pixel mini-LED panels light each pixel or a tiny cluster individually, so they show essentially no bloom.
Is some blooming normal?
Yes — on any zone-dimmed LCD, a little bloom around small bright objects on black is expected and not a defect. It only matters if it bothers you in real use: letterbox bars in films, subtitles, star fields, or a mouse cursor on a dark desktop. The more dimming zones a panel has, the less you will notice it. If you want zero bloom, that is an OLED strength.
How is blooming different from backlight bleed?
Backlight bleed is light leaking at the edges and corners of the panel, visible on an all-black screen even with nothing bright shown. Blooming is light spreading around a bright object elsewhere on the screen — it only appears when something bright is on a dark field. Use the backlight-bleed test for edge leakage and this blooming test for halos around highlights.