Two monitors can both claim HDR support and look wildly different, and the reason usually comes down to local dimming zones. This is the feature that lets an LCD produce convincing bright highlights against dark backgrounds, and the number of zones is one of the most meaningful HDR specs you can check. Here is how it works and what counts as enough.
Why LCDs need local dimming for HDR
An LCD does not make its own light; it filters a backlight. If the whole backlight is one big lamp, a bright star in a night sky forces the entire panel to stay lit, washing the blacks to gray. Local dimming splits the backlight into independently controlled zones so dark areas can dim or switch off while bright areas blaze, dramatically improving contrast in HDR.
Edge-lit vs full-array
Cheaper edge-lit dimming places LEDs along the borders and controls a handful of columns, which is crude. Full-array local dimming (FALD) places LEDs directly behind the panel in a grid of dozens to thousands of zones, giving far finer control. Mini-LED takes this further by shrinking the LEDs so thousands of zones fit, approaching OLED-like contrast.
How zone count changes the picture
| Zones | Typical tech | HDR quality | Main artifact |
|---|---|---|---|
| 0 (edge, no local) | Basic “HDR400” | Marginal, raised blacks | No real contrast gain |
| 8-32 | Edge-lit dimming | Slightly better | Obvious blooming |
| 384-1152 | FALD / entry mini-LED | Good | Some halo on bright objects |
| 2000+ | High-end mini-LED | Excellent | Minimal, subtle blooming |
The blooming trade-off
What blooming is
Because each zone covers many pixels, a small bright object like a mouse cursor or subtitles on black can light up its whole zone, creating a faint halo around it. More zones make each zone smaller, so the halo shrinks and blooming becomes harder to see. This is the core reason zone count matters so much.
Where OLED differs
OLED sidesteps the whole issue because every pixel is its own light source, so there are effectively millions of zones and no blooming at all. The trade-off is lower peak brightness on some models and burn-in risk. Mini-LED with thousands of zones is the LCD world’s answer, offering higher brightness with only slight blooming.
What to look for when buying HDR
Ignore bare “HDR” logos and low DisplayHDR tiers without dimming; they add little. Look for a stated dimming type and zone count, aim for at least a few hundred zones for genuinely good HDR, and pair that with high peak brightness (600 nits and up, ideally 1000+). For dark-room movie and game HDR, more zones or OLED will always look more convincing than a bright but zone-poor panel.
Why the dimming algorithm matters as much as zones
Zone count is the headline, but the control algorithm decides how good the result feels. A panel with many zones but crude logic can still show visible pumping, where the backlight brightens and dims noticeably as content changes, or crushed shadow detail as it dims too aggressively. A well-tuned panel with fewer zones sometimes looks calmer than a poorly tuned one with more, so reviews of the actual behavior matter.
Refresh-rate interaction is another subtlety. Fast-changing game scenes stress the dimming system, and some monitors disable or soften local dimming at high refresh to avoid lag and artifacts, which quietly reduces HDR impact exactly when you are gaming. Before buying for HDR gaming specifically, check that strong local dimming remains active at your target refresh rate, not just in a slow test pattern, because a great zone count is wasted if the feature backs off under motion.
FAQ
Is more zones always better?
Generally yes, because smaller zones mean finer contrast control and less blooming. Quality of the dimming algorithm matters too, but between two similar panels the one with more zones will almost always deliver cleaner HDR highlights against dark backgrounds.
Do I need local dimming for SDR gaming?
No. Standard dynamic range content does not demand the extreme contrast that dimming provides, and aggressive dimming can even cause distracting brightness shifts in SDR. Local dimming earns its keep in HDR movies and games; for everyday SDR use it is often best left off.
Bottom line
Local dimming zones are what turn an HDR label into real HDR on an LCD. Edge-lit designs with a handful of zones barely help, while full-array and mini-LED panels with hundreds to thousands of zones deliver striking contrast with minimal blooming. Check the zone count and peak brightness, not just the HDR badge, and remember OLED avoids the problem entirely.
