How to spot local dimming halos around bright shapes

A bright cursor, subtitle, or star on a dark screen can seem to have a cloudy glow around it. If your TV or monitor has local dimming, that glow may come from the backlight zones brightening around the object. Some haloing is a normal side effect, but a repeatable test can help you tell it from a pixel defect or another display problem.

Use a dark scene with a small, bright shape, then compare the display with local dimming at different settings. The Display Test can also help you check for pixel and color problems, although its color checks do not reproduce every local dimming pattern.

Test for halos around bright shapes

1. Open the Display Test and use its color checks to look for individual pixels that stay a different color. Then open a dark scene or image with a small white object on a mostly black background. A cursor on a dark background can work, but a moving shape is harder to judge.
2. Set the screen to its normal resolution and sit in your usual viewing position. Dim the room lights, but do not change the screen brightness during the comparison.
3. Look at the bright shape from directly in front. Note whether the surrounding glow follows the shape, appears as a large fixed patch, or stays in the same place when the image changes.
4. Open the TV or monitor's on-screen menu and compare local dimming at its current setting, a lower setting, and off if that option is available. Use the same scene and viewing position each time.
5. Repeat the check with a second dark scene or image. A single scene may have compression, reflections, or other details that look like a halo.

Keep the screen at a comfortable brightness. You do not need a flashing pattern or a full-white screen to check local dimming.

What the result means

A soft glow follows the bright object

This is consistent with local dimming blooming. The display lights a group of backlight zones to show a bright object, and some light spills into nearby dark areas. Smaller zones and stronger contrast control can reduce the effect, but many displays cannot eliminate it completely.

A broad cloudy patch stays in one place

Check whether the patch changes when local dimming is turned off. If it does, it is probably related to the backlight zones. If it remains in the same place, check for reflections, uneven panel illumination, or a viewing-angle effect. Compare from your usual seat, since some screens look less uniform when viewed from the side.

One tiny spot stays the same color

A single red, green, blue, or white point that stays fixed while the image changes may be a stuck pixel. A point that stays black may be a dead pixel, though a mark on the surface or a signal issue can look similar. Use the Display Test's solid colors to check whether the spot remains visible across different backgrounds. For more on identifying pixel defects, see stuck pixel vs. dead pixel.

The glow disappears when local dimming is off

That points to a display processing effect rather than a defect in the image source. Turning local dimming off may reduce halos, but it can also make dark areas look gray and lower perceived contrast. Choose the setting that looks best in the room where you use the screen.

How to reduce distracting halos

1. Compare the local dimming levels. Try a lower or less aggressive setting in the display's on-screen menu. Names and available levels vary by model. A lower setting can make halos less obvious, but may also make the picture less punchy.
2. Check the picture mode. Compare a standard or cinema picture mode with the mode you normally use. Some modes change contrast or local dimming behavior. Keep other settings steady so you can tell which change matters.
3. Check HDR only if the source uses it. On Windows 11, open Settings › System › Display › HDR on a compatible display and compare the same HDR content with the setting on and off. On macOS, open System Settings › Displays and check the selected display's HDR options, if available. HDR changes how highlights are presented, but it does not repair a display's dimming zones.
4. Reduce nearby reflections. Move a lamp or bright window reflection out of the screen's reflection path. Reflected light can make black areas look gray and exaggerate the apparent glow.
5. Update the display firmware if the manufacturer offers an update. Follow the instructions for your exact model. An update may change image processing, but do not assume it will remove a halo that comes from the panel design.
6. Compare another input or source. If the effect appears only with one device, app, or video, check that source's picture settings and cable connection before treating the display as faulty.

When it may be a display fault

Local dimming halos are usually soft and change with the bright content. A fixed bright patch, a dark vertical band, or a cluster of abnormal pixels that remains visible across different images and settings is more concerning. Repeat the check after the display has warmed up, then compare with another input. If the defect persists and the screen is under warranty, take clear notes about the settings and scenes that reveal it, and contact the manufacturer before attempting a repair.

Why photos can make halos look worse

A phone camera does not see the screen exactly as your eyes do. Automatic exposure can brighten dark areas, and the camera's processing can add glare or change contrast. Judge the display directly from your normal viewing position. A photo can help document where a defect appears, but it is not a reliable measurement of how strong the halo looks in person.