Blooming

What blooming is

Blooming, also called the halo effect, is light from a bright object leaking into the dark area around it. It belongs to LCD TVs that dim their LED backlight in zones. Screen Resolution Test puts it simply: "It occurs when light from a bright zone spills over into adjacent darker zones." The usual victims are subtitles, credits, a cursor, a street light, and stars on a black sky. How-To Geek notes that "all LED-backlit LCD TVs with full-array local dimming suffer from blooming" to some degree, and Display Ninja adds that for most content it is "negligible," with night skies and fireworks as the extreme cases.

How blooming works

A local-dimming LCD can only change brightness per zone, while the liquid-crystal layer works per pixel. Zones are far larger than pixels. A 3840 x 2160 panel has 8,294,400 pixels. An edge-lit set with 10 to 32 zones, the range Screen Resolution Test gives for the type, puts between about 259,000 and 829,000 pixels in each zone. A full-array set with 1,152 zones, such as the BenQ EX321UX monitor Display Ninja cites, has 7,200 pixels per zone. The TCL QM8L that eCoustics tested has up to 4,000 zones on its 98-inch size and 2,584 on the 75-inch model, which is about 2,074 and 3,210 pixels per zone. A few hundred bright pixels of subtitle text therefore light a patch of thousands of pixels, and the surrounding glow is the halo you see.

Display Ninja lists three causes: the zone count, the local dimming algorithm, and scene complexity. The algorithm decides how hard to light a zone when a bright pixel sits next to dark ones, and it trades halo size against clipped highlights. How-To Geek describes the user-facing side: a low local dimming setting dims the backlight less and makes blooming less noticeable, while a high setting raises contrast and makes the halo more visible.

Blooming vs OLED and dual-cell panels

OLED pixels emit their own light, so a true halo from light bleed "doesn't happen on OLED displays," as Digital Trends puts it. The cost is lower sustained brightness in bright scenes. VESA's DisplayHDR True Black tiers show the gap in numbers: a maximum black level of 0.0005 cd/m2 on a checkerboard at full luminance. The ITU-R BT.2100 reference display allows a black of 0.005 cd/m2 or less.

A dual-cell LCD attacks the problem differently, with a second monochrome panel that gates light per pixel. Reviewed.com measured a Hisense U9DG black level of 0.005 cd/m2 against an OLED's 0.000, with 1,119 nits sustained on a 20% white window, and found that "instances of light bloom" were "almost non-existent." That puts it level with the BT.2100 ceiling. The U9DG list price was $2,999.99 for the 75-inch model.

Why HDR makes blooming easier to see

The halo is the same light in SDR and HDR, but HDR pushes the bright object much harder while the neighbors stay near black. Display Ninja notes that LED-backlit displays "cannot produce true blacks," which is why local dimming exists. A highlight near the 1,000 nits that BT.2100 expects of a reference display drives its zone harder than a dimmer SDR highlight would, so the zone spills more absolute light into the black around it. Dark rooms are therefore where the dimming settings and the test scenes below matter most.

Which TVs bloom the least

Zone count alone does not settle it, but it helps. eCoustics tested the 2026 TCL QM8L in a lab and reported "virtually no backlight blooming," along with 1,992 nits on a 10% window and 708 nits on a full white screen in Filmmaker Mode, against a 6,000-nit claim it could not reproduce. DisplayHDR sets a floor by tier: DisplayHDR 500 and 600 need at least 1D local dimming, DisplayHDR 1000 and 1400 need 2D, and the minimum static contrast ratio rises from 1,300:1 at DisplayHDR 400 with 1D dimming to 30,000:1 at DisplayHDR 1000 and 50,000:1 at DisplayHDR 1400. See local dimming zone count, full-array local dimming, mini-LED backlights, and RGB mini-LED for the next step. I could not find a published zone count for the Hisense UR8 or the Sony BRAVIA 7 II in pages that loaded, and brands often quote "up to" figures for their largest size only.

How to check for it

Use a scene with a small bright object on pure black. A star field, end credits, or a subtitle in a dark scene works. View it in a dark room with the picture mode you actually use, because the halo grows with brightness. Compare the same scene with local dimming set to low and to high: if the halo shrinks but black turns gray, you are seeing the contrast cost How-To Geek describes. Digital Trends reports that complaints "have largely disappeared among owners of mid- to upper-range TV models," and that blooming was common in TVs as recently as 2020.

Common confusions

Blooming is not backlight bleed at the edges and it is not black crush; it is specific to zone-based dimming. Streaming compression can also create halo-like artifacts around edges, which is not backlight behavior, so check a disc or a clean test pattern before blaming the TV. And more zones do not guarantee a clean image: How-To Geek's wording is that fewer zones covering bigger areas can mean more blooming, and that more zones can reduce it, not eliminate it.