Backlight Bleed Test
Fill the screen with black and grey to find bleed, glow and clouding.
Look at the edges and corners for glow or patchy light.
Turn the lights off and let your eyes adjust for a minute first. Judge from a normal viewing distance — every panel looks worse from six inches away and at full brightness.
Your test runs locally in your browser. No device data is uploaded.
How to use the backlight bleed test
Turn the lights off and give your eyes a minute to adjust, then run the test fullscreen at the brightness you normally use. Start on black and look along each edge and into the corners, then step through the grey screens to check the middle of the panel for clouding and patchiness.
Bleed, glow and clouding are different things
Backlight bleed is light escaping around the edges of the panel, usually as bright patches or streaks at one edge. It stays in the same place when you move your head, and a severe case is a manufacturing defect worth returning.
IPS glow is a broad wash of light in the corners that shifts or disappears as you change viewing angle. Every IPS panel has it to some degree and it is not a fault. Moving your head is the quickest way to tell the two apart.
Clouding is uneven patchiness across the middle of the panel, easiest to see on a dark grey field rather than pure black, and usually caused by uneven pressure in the assembly.
Judging it fairly
Photographs exaggerate bleed dramatically, because a long exposure gathers far more light than your eye does. Judge at your normal viewing distance and brightness, on content you actually watch. If you cannot see it during a dark film scene, it is unlikely to bother you in practice.
OLED panels have no backlight at all, so an OLED with apparent bleed is showing something else entirely.
Frequently asked questions
- What is the difference between backlight bleed and IPS glow?
- Backlight bleed is light escaping around the edges of the panel, and it stays put when you move your head. IPS glow is a wash of light in the corners that changes or disappears as you shift viewing angle. Bleed can be a defect; glow is a characteristic of the panel type.
- How should I judge it?
- In a dark room, after letting your eyes adjust for a minute, at your normal viewing distance and brightness. Every LCD looks alarming photographed in the dark at full brightness from six inches away, and that is not how you use it.
- How much bleed is normal?
- Some is normal on almost every edge-lit LCD. It matters when you can see it during ordinary dark content such as film letterboxing or night scenes, rather than only on a deliberate black test screen. OLED panels have none, because unlit pixels emit no light.
- What are the grey screens for?
- Uniformity. A pure black screen shows edge bleed, but large-scale unevenness, clouding and tinting are far easier to see on a dark grey or mid grey field.