Backlight bleed test

A pure black full screen, which is the only way to see light leaking in from the edges.

Escape or one tap comes back.

Every colour, one tap away

Brightness, timer and colour cycle

What backlight bleed actually is

An LCD panel does not produce its own light. A backlight behind it is always on, and the liquid crystal layer in front of it acts as a shutter. Black is that shutter closed as far as it will go, which is never all the way. Where the panel is not perfectly sealed against its frame, usually at the corners and along the edges, light escapes around the shutter instead of through it. That is bleed.

It is a manufacturing tolerance, not a failure mode, and essentially every LCD has some. OLED panels have none at all, because a black pixel on an OLED is simply switched off.

How to test it honestly

  • Set the monitor to the brightness you actually use. Testing at 100 percent brightness is how a perfectly good monitor gets returned.
  • Dim the room rather than blacking it out completely, and give your eyes a full minute to adjust before judging anything.
  • Look at the screen straight on from your normal seating distance. Bleed always looks worse from an angle and worse from close up.
  • Do not photograph it. A long camera exposure makes mild bleed look like a searchlight, which is why every forum post about bleed looks alarming.

Bleed, clouding and IPS glow are three different things

  • Bleed comes in from the edges and corners as distinct patches or streaks. It stays put when you move your head.
  • Clouding, or mura, is a broad soft haze in the middle of the panel. It is more annoying than edge bleed because it sits where you look.
  • IPS glow is a silvery wash in the corners that changes or vanishes as you move your head. It is inherent to IPS panels and is not a defect. No replacement will be free of it.

When it is worth returning a monitor

The test is whether you can see it during normal use. If a dark scene in a film or a black terminal window shows an obvious bright corner from where you sit, that is worth acting on inside the return window. If you can only find it by turning the lights off and pushing the brightness to maximum, every replacement you order will look the same, and you will have spent a week of shipping to learn that.

Frequently asked questions

Is backlight bleed normal?

On an LCD, some amount is present on essentially every panel, because the liquid crystal shutter never closes completely and the seal around the edges is a manufacturing tolerance. OLED panels have none at all, since a black pixel is simply switched off.

How much bleed is too much?

The honest test is whether you can see it during ordinary use, at the brightness you actually use, from where you actually sit. If a dark film or a black terminal window shows an obvious bright corner, act on it inside the return window. If you can only find it with the lights off at maximum brightness, every replacement will look the same.

Why does my bleed look worse in photos?

Because a long camera exposure gathers far more light than your eye does. Photographs of mild bleed look like searchlights, which is why forum posts about it are so alarming. Judge it with your eyes, not a camera.

What is the difference between bleed, clouding and IPS glow?

Bleed comes in from the edges and corners as distinct patches and stays put. Clouding is a broad soft haze across the middle of the panel. IPS glow is a silvery wash in the corners that changes or vanishes as you move your head, and it is inherent to the panel type rather than a defect.