Blooming / halo test

Spot blooming and halation from local dimming. Small bright shapes on a pure black field reveal grey glow around highlights — common on Mini LED and some HDR panels when dimming zones light more area than the highlight needs.

Bloom pattern

Highlight sizing

Spot size 24px Bar height 8% Cross line width 2px Star spacing 64px Move speed 3 px/frame

Highlight Background

What to look for

Tight highlights

Bright elements stay crisp on black with little or no grey glow around them — local dimming zones are well controlled.

Visible bloom / halo

Grey wash spreads beyond the highlight, trails a moving spot, or lifts letterbox/subtitle bars into murky zones — lower local dimming or try a cinema/game mode.

Run & cycle

Hold time 6s Auto-cycle in fullscreen Walk every bloom pattern

← → Cycle patterns
F Fullscreen

Free blooming test — local dimming halos on black

A browser blooming / halo instrument with center and corner spots, thin cross, subtitle bar, star field, moving highlight, and letterbox bars. Adjust spot size, bar height, line width, spacing, and speed. Built to reveal local-dimming bloom — not a lux meter, HDR certification, or repair tool.

Classic bloom stressors

Subtitle bar and letterbox patterns recreate HDR text and cinema bars on black — the cases Mini LED owners notice first.

Stars & moving spot

Dense star fields light many zones at once; the animated spot shows whether bloom trails or pulses as dimming chases the highlight.

Fine geometry

Thin crosses and adjustable spot size expose halation width. Glow that outruns the line is bloom, not just panel glare.

HDR capability badge

A live browser HDR hint sits beside the pattern list — useful context, not proof that local dimming is active on your TV.

Blooming vs bleed — what you are seeing

Not every glow on a black screen is the same fault. Blooming is dynamic and follows bright content; backlight bleed is static edge leak.

Local dimming zones

Mini LED and FALD backlights divide the panel into zones. When a zone turns up for a highlight, neighbors can lift too — that grey skirt is blooming.

Halation / bloom

Bright content on dark backgrounds causes nearby blacks to look milky. Severity rises with aggressive local dimming, high peak brightness, and small highlights.

Not backlight bleed

Bleed is fixed light leaking at edges on a full black field. Blooming appears around objects and can move. Use the dedicated bleed test for edge uniformity.

Browser limits

This page draws bright-on-black patterns; it cannot force your TV into HDR or measure zone size. Results depend on the display mode you actually enable.

How to run the blooming / halo test

Work in a dark room, pick one pattern at a time, and change only one TV setting between passes so you know what fixed the halo.

Dark room, honest mode

Kill bias lighting and open the pattern fullscreen on the display under test. Note whether local dimming / Mini LED / FALD is on, and which picture mode you used.

Tip Avoid “Vivid” first — start with Cinema, Filmmaker, or Game and compare from there.
Stress with bar and center spot

Run Subtitle bar, then Center highlight. Grey glow that spreads beyond the bright edge is bloom. Tight whites with deep blacks nearby mean zones are well controlled. See also: backlight bleed test .

Tip Enlarge spot size if the halo is hard to see; shrink it to judge fine control.
Check motion and density

Advance to Star field and Moving highlight. Trailing or pulsing grey around the moving spot means laggy or aggressive dimming — try a lower local-dimming level. See also: HDR test .

Tip Finish with Letterbox bars if you watch 21:9 content often.

What this test cannot certify

Not an HDR lab grade

Peak nits, zone counts, and ANSI contrast need instruments. This tool only makes bloom easier to see by eye.

Mode-dependent results

The same panel can bloom hard in one OSD preset and look clean in another. Record the mode with your notes.

When blooming checks matter

Use this when dark-scene content shows milky rings around stars, UI, or subtitles — not for every dead-pixel hunt.

New Mini LED TV

Credits and subtitles glow on black letterbox
Star fields look foggy between points
Game mode feels brighter but milky in shadows

Recommended Lower local dimming one step, retest subtitle bar, then decide if the trade-off beats crushed blacks.

HDR desktop / creative monitor

Bright cursors or windows lift nearby blacks
Thin white UI lines show soft halos
Comparing SDR vs HDR Windows paths

Recommended Toggle HDR OS settings and retest thin cross; if bloom is worse in HDR only, keep SDR for dark UI work.

Setup tips for clearer bloom reads

Kill ambient wash

Room light reflecting off the panel fakes halos. Test in a dark or dim room facing the screen square-on.

One setting at a time

Change local dimming, contrast enhancer, or peak luminance separately so you know which control tightened the halo.

Warm up a few minutes

Some sets change zone behavior after warm-up. Give the panel a short settle before judging.

Separate bleed from bloom

If corners glow on a full black field with no highlights, run backlight bleed next — that is a different defect.

Blooming / halo test FAQs

What is blooming?

Blooming (halation) is when bright content on a dark background makes nearby pixels look grey or milky. It happens when local dimming zones raise brightness over a larger area than the highlight itself.

How is blooming different from backlight bleed?

Backlight bleed is static light leaking at edges or corners on a dark screen. Blooming is dynamic — it appears around bright objects when local dimming activates. Use the backlight bleed test for edge uniformity.

Can a browser fix blooming?

No. This tool only helps you see it. Fixes live in the display menu (local dimming strength, picture mode, peak brightness) or in panel/firmware design — not in the webpage.

Why use a subtitle bar pattern?

HDR subtitles and credit rolls are classic bloom triggers on Mini LED TVs: a bright horizontal band on black letterbox. The subtitle bar mimics that stress without needing a disc or streaming app.

Does the HDR badge mean blooming will appear?

No. The badge reports whether the browser thinks HDR is available. Blooming depends on your panel’s local dimming behavior and the picture mode you select.