Backlight Bleed Test — Check for Light Leak and IPS Glow
An LCD does not make black — it makes white and then blocks it. Where the blocking is imperfect at the panel edges, light escapes: that is backlight bleed. A pure black full screen in a dark room is the only way to see how much your panel has.
What people use the backlight bleed test for
Assess a new monitor or TV
Bleed is one of the most common reasons for an exchange, and one of the easiest defects to miss during normal use. Test in the first few days.
Tell bleed apart from IPS glow
They look similar and are not the same thing. Bleed is a manufacturing fault; glow is inherent to the panel technology. The test below distinguishes them.
Document a warranty claim
Photograph the black screen in a dark room at a normal exposure — not a long one, which exaggerates the problem and gets claims rejected.
Judge a panel for dark-room use
If you watch films or play games at night, bleed matters far more than it does in a bright office. Test in the conditions you will actually use it in.
How to use the backlight bleed test
- 1Turn off every light in the room and let your eyes adapt for a couple of minutes.
- 2Press F for fullscreen so nothing but black is on the panel.
- 3Set the display to your normal brightness — not maximum, which exaggerates everything.
- 4Sit at your usual viewing distance, straight on, and look at the edges and corners.
- 5Now move your head off to one side: glow that shifts or fades as you move is IPS glow, patches that stay put are backlight bleed.
Frequently asked questions
Backlight bleed or IPS glow — how do I tell?+
Move your head. IPS glow is a viewing-angle effect: it appears as a silvery haze in the corners, changes as you shift position, and every IPS panel has some. Backlight bleed is physical light escaping the edge — it stays in exactly the same place no matter where you sit, and often looks like a bright cloud or a distinct streak.
Is some bleed normal?+
Yes. Nearly every edge-lit LCD has a little, and manufacturers do not consider mild bleed a defect. It is worth an exchange when it is clearly visible during ordinary dark-scene viewing rather than only on a full black screen in a blacked-out room.
Do I need to install anything?+
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Is it free?+
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