Backlight bleed test

Run it in a dark room

A dark room makes bleed easy to find. Keep your everyday brightness: DisplayNinja suggests 20% to 50% and expects some bleed on black at 100% in the dark. Sit centered and wait for the controls to fade; they give off light too.

Dell inspects monitors in 150 lux of room light, 70 lux for gaming models. It says leakage should ideally not be judged in a dark room, where some leakage on dark images is within specification. So check again in normal light before you claim or return a screen.

Run the test with local dimming on and off. Dimming switches zones off behind dark areas, so all-black can look cleaner than a dark scene with a bright object. RTINGS notes that some monitors lock dimming on in HDR, and the HDR test shows how to switch HDR off.

Backlight bleed or IPS glow

• Backlight bleed Light along the edges or in the corners that stays put wherever you sit, as DisplayNinja defines it.
• IPS glow Brighter corners on an IPS panel, seen only at an angle, RTINGS explains.
• Blooming A halo around a bright object on a local dimming monitor, which RTINGS traces to a whole zone lighting up. Plain black does not show it.

Phone photos exaggerate bleed and glow, KTC and DisplayNinja warn, so judge by eye. A single lit dot is a stuck or hot pixel, not bleed. An OLED has no backlight to leak, so check it for burn-in instead.

How much bleed is normal

We found no maker or standard that puts a number on it. Dell's pixel guidelines class edge bleeding as something other than a pixel defect.

Standard deviation from even black, measured by RTINGS on a white cross on black (2025); lower is better. Single monitors vary, so these are averages, not a pass mark.

Return or keep

DisplayNinja says to return a display whose bleed shows in normal use, and to keep one whose bleed only a test shows. A replacement can be worse, or bring dead pixels. Decide within the return window: RTINGS's long-run TV tests showed that uniformity can get worse.

Dell's guides for monitors and laptops send you to support when the leak shows in normal room light or the screen is clearly worse than another of the same model.

How the backlight bleed test works

The first field is pure black, level 0 of 255, on every screen pixel. The second adds corner guides, four dark gray brackets 1 CSS pixel thick, set in from the corners so their own light stays small. A local dimming monitor can still light the zone behind them, the blooming RTINGS describes, so judge bleed on plain black. The third, a 10% gray at level 26 of 255, stands in for a dark film or game scene.

You judge by eye; we measure no light, and we can't switch off local dimming, HDR or night light for you. On an iPhone the browser bars stay on screen, so you can't check the top and bottom edges. To check evenness on white, gray and color, use the monitor test.