How to use this test
- Set a comfortable normal brightness. Start with your usual room lighting, rather than an extreme exposure.
- Open the black background in fullscreen and hide the controls. Sit at the normal viewing distance.
- Move your viewing position slightly. Note whether a bright area changes strongly with angle or stays fixed near an edge.
- Compare a dark scene or application you actually use. Record your own observation and the brightness setting outside the tool.
Read the observations
This test can help you describe visible non-uniformity, but it cannot establish its cause. LCD glow can change with viewing angle, while edge light leakage may look more fixed. Reflections, panel technology, local dimming and room lighting complicate the comparison. A phone camera with automatic exposure can make a faint patch look much brighter than it does to your eyes. For a support request, describe normal-use conditions and follow the manufacturer’s evidence requirements.
What this test cannot tell you
This is a black background, not a luminance meter. It cannot read brightness settings, identify your panel technology or quantify a leak. OLED displays do not use an LCD backlight, so “backlight bleed” is not the same diagnosis for them. Do not press the panel or adjust its chassis based on this test. Use the separate colored-background test for isolated pixel concerns.
Need a closer comparison? Backlight bleed or glow: make the visual comparison useful.
Questions about the test
Is glow always a defect?
No. Viewing-angle behavior depends on panel technology. Compare normal-use conditions and ask the manufacturer about the specific model.
Can the page measure the bright area?
No. You inspect the physical panel. Any assessment saved in the report is entered by you.
Technical references
Method version 2.0 · Page updated 2026-10-20