Dead Pixel & Backlight Bleed Test

How to use this dead pixel and bleed test

Press Start full test to go full screen and step through 24 screens: dead pixels, backlight bleed, uniformity and banding, and OLED burn-in. Use the cards to run one section. Wipe the screen with a soft cloth first so dust is not mistaken for a pixel defect.

• Next: tap or click, or press → or Space. Tap the left 30% of the screen or press ← to go back. Swiping also works.
• Mark a defect: long-press for half a second or right-click. A ring stays on screen across colors and the grid cell (e.g. C4) and pixel coordinates are saved to your report.
• Grid: toggle with the Grid button or the G key.
• Exit: Esc or ✕. Advancing past the last screen ends the test and takes you to the report.
• The toolbar and cursor hide automatically. Safari on iPhone does not support full-screen web pages, so rotate to landscape there.

Dead, bright and stuck pixels

Each pixel has red, green and blue subpixels. Following Dell’s definitions:

• Dead (dark) pixel: all three subpixels off — a black dot, easiest to see on white.
• Bright (hot) pixel: all three subpixels always on — a white dot, easiest to see on black.
• Stuck subpixel: one subpixel always on — a red, green or blue dot.
• Dark subpixel: one subpixel off — a dark dot visible only on some colors, which is why you should step through every color.

Backlight bleed vs IPS glow

Dell explains that light leakage (bleed) stays the same regardless of viewing angle and distance and can be considered a defect if it significantly affects viewing, while IPS glow mostly affects corners, changes with viewing angle and distance, and is not a defect. BenQ likewise notes IPS glow is technology-related and cannot be completely eliminated.

Check in a dark room at your normal brightness, sitting straight on at your usual distance. Photos can look brighter or darker than reality depending on camera exposure, so judge with your eyes and use photos as a record.

Uniformity, banding and OLED burn-in

On the 25/50/75% gray screens, look for clouding or tinted areas. On gradients, check for wide bands. On the 32-step grayscale, the darkest steps should remain distinguishable.

OLED burn-in comes from uneven use: the more an OLED pixel is used, the dimmer it gets compared with less-used pixels, so static taskbars, logos and HUDs can leave faint shapes. It may also be temporary image retention. Samsung recommends running Pixel Refresh on its OLED monitors and LG recommends Image Cleaning in the OLED Care menu; run these and re-test before deciding it is permanent.

Pixel policies, ISO classes and documenting a return

Pixel policies are set by each manufacturer or seller. Dell, for example, publishes a policy to replace eligible displays for even one bright pixel during the warranty period. The old ISO 13406-2 standard defined pixel fault classes — Class II allowed 2 bright, 2 dark and 5 subpixel defects per million pixels — but these were guidelines, and the standard has been withdrawn and replaced by ISO 9241-307 and related parts.

If you find a defect, photograph or film it on the relevant color with the marker ring visible, copy this report (resolution, counts, cell and coordinates), keep the box, and contact the seller before its return window closes.