Backlight bleed test. Black and grey, in the dark.
A backlit screen leaks light at its edges when the panel is pressed unevenly in its frame, and some clouds across the middle. Both show only on dark fields with the lights down. The screen fills with black, then 25% grey; you say whether it looked even, bright at the edges or corners, or clouded. Edges are common and informational; clouding is the one worth raising on a new screen.
One check
- Uniformity and backlight bleed
One check after another, with your progress along the top and a plain verdict on each. Nothing you show the camera or say into the microphone leaves this page.
What it measures
Measured here, not assumed.
- Black, full screen
- Where bleed and IPS glow show: bright patches at the edges and corners.
- 25% grey, full screen
- Where clouding and uneven brightness show: darker or lighter patches across the picture.
- What you saw
- Even, bright edges or corners, or clouding. Only clouding warns; the rest is recorded for information.
If it fails
The usual failures, and what fixes each.
- Bleed or IPS glow?
- Move your head side to side, or tilt the screen. IPS glow changes and shifts with the angle and fades when you sit back; bleed stays in the same place and the same shape from every angle.
- Bright corners on a new screen
- If it stays put when you tilt and shows in what you watch with the lights on, use the seller's return window. Lowering the brightness shrinks it; it rarely gets better on its own.
- Clouding
- Patches that stay where they are across dark scenes. On a new screen, raise it with the seller inside the return window; a photo at a short exposure helps, but say it is exaggerated.
Where a browser stops
What it cannot tell you.
- Your eyes judge it. A page cannot measure light, and a phone camera is no help: a photo exposes for the dark and exaggerates bleed far beyond what the eye sees.
- Bleed depends on the brightness setting; judge at the one you use.
- An OLED has no backlight, so it has no bleed; uneven grey there is a different fault.
Privacy
Nothing leaves this page.
The camera and microphone are read on this page and stopped as soon as they have been measured. The clip you can play back lives in the browser's memory and is discarded when you leave. The location check discards the position. The internet test sends random bytes to this site and nothing else. The result is stored nowhere unless you ask for it by email, and then only the fact that an email was sent is kept.
Questions
Backlight bleed test, answered
- How do I test for backlight bleed?
- Darken the room, set your normal brightness, and fill the screen with black. Look at the edges and corners. Then move your head: what moves with you is IPS glow, what stays is bleed.
- Is some backlight bleed normal?
- A little at the corners is common on backlit panels and is usually invisible with the lights on. It becomes a reason to return a screen when it shows in ordinary use.
- Why does my photo of the bleed look so bad?
- A camera in a dark room raises its exposure to see anything, which makes faint glow look bright. Judge by eye at the brightness you use.
- What is the difference between IPS glow and bleed?
- IPS glow comes from the panel's viewing angle: it shifts and changes as you move. Bleed comes from light escaping at the edges: it stays in one place.
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