Backlight bleed test

How to run the backlight bleed test

1. Let the screen warm up for a few minutes. Set the brightness you normally use and turn off dynamic contrast if you can.
2. Darken the room and wait a minute for your eyes to adapt.
3. Press Start backlight bleed test. The screen fills with pure black. Press H to hide the hint text.
4. Click, press Space or → to step to near black, 5% grey and 10% grey; ← goes back. Esc exits.
5. Look at the centre from your usual distance, then move your head left, right, up and down, and finally step back a metre or two.

Bleed, IPS glow or clouding?

• Backlight bleed: bright patches or streaks along the edges or in the corners that stay in place when you move your head. Light from the backlight leaks past the edges of the panel. It is easiest to see on pure black.
• IPS glow: a greyish, sometimes warm or bluish sheen, mostly in the corners, that changes or fades as you move your head or step back. It comes from viewing an IPS panel at an angle and is stronger close to large screens.
• Clouding: uneven, blotchy patches spread across the screen rather than at the edges, most visible on near black and 5–10% grey. For lighter greys and banding, use the monitor uniformity test.
• OLED screens have no backlight, so they cannot bleed; look for uneven near-black areas instead. Screens with local dimming may switch zones off on pure black, which hides bleed but can show halos around bright objects in normal content.

Judging what you see

• Judge with your eyes. Phone cameras on automatic exposure brighten a dark scene and make bleed and glow look much worse; if you take a photo for a claim, lower the exposure until the photo matches what you see.
• Some bleed and glow is common on LCD screens. Whether it counts as a defect depends on the retailer's or manufacturer's policy for that model and on whether it bothers you in normal content such as dark films or games.
• This page shows test fields; it cannot measure brightness or grade the severity of what you see.
• Do not press on the panel to try to reduce bleed: it can damage the screen. Lower brightness or a light behind the monitor makes bleed less noticeable in daily use.

For a single plain black field for other uses, open the black screen; for bright or stuck pixels, use the dead pixel test.