Backlight bleed and clouding test
Pure black fields at several levels, so you can see light leaking around the edges of an LCD panel. Best done in a dark room, and worth doing in the first two weeks of owning a set, while you can still return it.
The test
This test needs JavaScript to run. Everything below still explains what to look for and what a bad result means, so the page is useful either way.
Turn the lights off first
Backlight bleed is only visible in a dark room. Give your eyes a minute to adjust before judging anything, and view the screen straight on rather than from an angle.
How to read it
Nothing to fix. Some very slight variation is normal on any LCD.
Common on IPS panels and usually considered normal. It changes as you move your head, which is how you tell it apart from real bleed.
That is backlight bleed. It does not change with viewing angle. Mild cases are common, obvious ones are a defect.
Clouding. Most visible in dark scenes and on panning shots. A strong case is worth a return.
An OLED has no backlight, so it cannot bleed. A perfectly black screen here is expected, not a test failure.
What this test can and cannot tell you
Panel defects are partly a judgement call. Here is where the line honestly sits.
You can see this clearly. A pure black field in a dark room is exactly how manufacturers check this themselves. Your eyes are the right instrument.
A judgement, not a measurement. There is no industry threshold. What matters is whether you can see it in normal viewing, on real content, at your normal brightness. If you have to hunt for it in a blacked-out room, most people stop noticing within a week.
Tell them apart by moving. IPS glow shifts and fades as you change viewing angle. Real backlight bleed stays put. This test cannot separate them for you, but that one movement will.
It will exaggerate it. Cameras raise the exposure on a dark scene, so photographs of backlight bleed always look far worse than the panel does. Judge with your eyes, not through a lens.
As black as the panel can go. We fill the screen with pure black. Any light you see is the panel, not the page.
Getting a fair look
Dark room, adjusted eyes
Switch the lights off and wait a minute or two. Your eyes need time to adapt, and bleed that looked severe at first often fades as they do.
Normal brightness
Judge at the brightness you actually watch at, not at maximum. Cranking the backlight to 100% makes any panel look worse and is not how you will use it.
Straight on, at your real distance
Look at the screen from where you normally sit. Bleed seen from 30 centimetres off-axis is not a problem you will ever experience in use.
Then watch something dark
The real test is a dark scene in a real film. If you cannot see it there, it is not worth returning a television over.
Questions people ask
What is backlight bleed?
On an LCD, the picture is made by shining a backlight through a panel that blocks light to make black. The blocking is never perfect and the edges are hardest to seal, so light escapes around the borders. It shows up as bright patches or streaks on a black screen.
Is some backlight bleed normal?
Yes. Almost every LCD has some, and manufacturers do not consider mild bleed a defect. What is not normal is bright obvious streaks or large cloudy areas that you can see during ordinary dark scenes.
What is the difference between bleed and IPS glow?
Move your head. IPS glow is a silvery haze, usually in the corners, that shifts and fades as your viewing angle changes. Backlight bleed stays in exactly the same place no matter where you look from. Glow is a characteristic of the panel type, not a fault.
Can backlight bleed be fixed?
Sometimes it settles slightly over the first few weeks as the panel and frame relax. Beyond that, no. It is a physical assembly issue. If it bothers you, the answer is a return or exchange, not a setting.
Should I return my TV for this?
Only if you can see it while watching normal content at your normal brightness from where you sit. If you have to darken the room and go looking for it, you will almost certainly stop noticing within a week.
My OLED shows nothing at all. Is the test broken?
No, that is the correct result. An OLED switches individual pixels off completely and has no backlight to leak, so a pure black field really is pure black.
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