Is Backlight Bleed Normal?
Usually, yes. The useful question is not whether you can see it in a dark room, but whether you can still see it in the light the makers test under.
Every edge-lit LCD leaks some light, and both Dell and ASUS describe leakage seen on a black screen in a dark room as normal. Dell says it inspects monitors under 150-lux ambient lighting, and gaming monitors under 70 lux; ASUS says to check with at least 150 lux and not in a dark room. So: find it in the dark if you want to see it, but judge it in normal room light, and compare with the same model before you decide.
Turn the lights off, open a black screen, and almost any LCD will show pale patches at its edges or corners. That is backlight bleed, and the first honest thing to say about it is that finding it proves very little. The makers expect it.
What it is
An LCD does not make its own light. A backlight behind the panel shines through, and the liquid crystal layer blocks that light to make black. Blocking is never perfect, and at the edges, where the light enters, it is least perfect of all. What escapes is what you see.
Dell describes it as light leakage that is “often noticeable around the edges or the sides of a monitor screen. Especially while it is displaying a dark background or is in a dark environment.” ASUS describes the same thing as illumination visible at the edges or sides of the screen, “especially when displaying a black background in a dim environment.”
Both go further than describing it. Dell states: “Some light leakage is to be expected when viewing images with dark backgrounds in dark rooms. These monitors are working as designed and are within specifications.” ASUS says leakage seen in a low-light environment is “considered a normal phenomenon” and that the screen “operates as designed and meets ASUS specifications.”
Seeing bleed in a dark room is not a finding. Seeing it in a lit room might be.
The lighting that decides it
This is the part most advice leaves out, and it is the part the makers are specific about.
| Maker | Condition stated |
|---|---|
| Dell | Monitors are inspected under 150-lux ambient lighting, described as similar to typical office lighting; gaming monitors are inspected at 70 lux. |
| ASUS | Check with at least 150 lux per unit area, for example typical office lighting, and do not check for light leakage in low-light environments such as dark rooms. |
Read on September 23, 2026 from each maker's own support page, linked below.
So there are two different jobs, and they need two different rooms.
- To see whether your panel leaks at all, darken the room. EIZO recommends testing in a dark room precisely because that is how dark areas can be judged, and it also suggests warming the monitor up first, ideally for 30 minutes.
- To decide whether it is a problem worth acting on, turn the lights back on to something like office brightness, and look again at the same black screen.
Most bleed that looks alarming in the first room is invisible in the second. That difference is the whole answer for most people.
Checking yours properly
- 1
Warm the screen up and clean it. Both change what you see, and a smear near a corner looks remarkably like a leak.
- 2
Open the Backlight Bleed Test full screen in a dark room and look straight on. Note where the patches are: corners, one edge, or spread across the middle.
- 3
Change the brightness. Dell's first troubleshooting step is to see whether the brightness level changes the issue. Bleed usually falls away sharply as brightness drops.
- 4
Now put the lights on, to something like normal office lighting, and look again. This is the condition the makers judge under.
- 5
Open something bright. Dell suggests checking the screen with bright applications open, to see whether the issue persists in the content you actually use.
- 6
Compare with the same model. Dell's own test is whether your screen is notably worse than other identical models. A shop floor, or a friend with the same monitor, settles it faster than any description.
Photographs exaggerate bleed badly. A camera in a dark room uses a long exposure, so it collects light your eye never notices. If you photograph it for support, do it under the lighting the maker names, and frame the whole screen so the picture shows the context rather than one bright corner.
When it is worth pursuing
Neither maker publishes a number you can measure yourself, and this guide is not going to invent one. What they publish instead is a route.
Dell: if the screen appears worse than comparable monitors, contact Dell Technical Support, and if possible provide an image of the fault so the technician can help further. ASUS: if the leakage persists under proper lighting, photograph it and contact an ASUS Service Center, where a technician evaluates it.
Two practical points sit alongside that. If the display is new, your retailer’s return window is usually simpler than any support conversation, and it does not require anyone to agree that the panel is defective. And bleed that only appears at an extreme viewing angle is worth re-checking straight on: the Viewing Angle Test shows how much your panel shifts as you move.
If the unevenness is spread across the whole picture rather than at the edges, that is a uniformity question rather than a bleed one, and the Screen Uniformity Test is the better tool: it holds a flat gray at three levels, which is where tint drift and cloudy patches show up.
What this page cannot do
It cannot measure light. A browser paints black, and your eyes and your room do the rest. It cannot tell you whether your panel is within your maker’s internal specification either, because that specification is not published as a number you can check.
What it can do is stop you returning a display for behaving exactly as designed — and, in the other direction, give you the maker’s own words and conditions when yours really is worse than it should be.
Questions
Is backlight bleed a fault?
Not by itself. Dell says some light leakage is to be expected when viewing dark backgrounds in dark rooms, and that such monitors are working as designed and within specifications. ASUS says leakage seen in a low-light environment is a normal phenomenon and that the screen meets its specifications.
Can I get rid of it?
No page, setting or software removes it, because it is light escaping from the panel's own edge lighting. Lowering brightness makes it less obvious, which is also why brightness is one of the first things Dell suggests changing when you check.
How bright should the room be when I judge it?
ASUS says to check with at least 150 lux, roughly typical office lighting, and specifically not in a dark room. Dell inspects monitors at 150-lux ambient lighting, and gaming monitors at 70 lux.
What if mine really does look worse than it should?
Dell's advice is to compare your screen with other identical models and, if yours is notably worse, to contact support with an image of the fault. ASUS asks for a photograph taken under proper lighting and sends it to a service center for evaluation.
Is clouding the same thing?
People use the words loosely. Bleed usually means brighter patches at the edges and corners; clouding usually means uneven patches across the middle. Both are unevenness in the same backlight, and both are judged the same way: in normal light, against another example of the same model.
How this guide was made
The judgement conditions on this page are quoted from the manufacturer pages listed below, with the date each was read. The test procedure is what ScreenTail's own Backlight Bleed Test does, described from the tool as it is built.
No numeric tolerance is given, because none of the makers publishes one: their pages state the lighting to judge under and then send you to a person. Any percentage or millimeter figure you find elsewhere is somebody's rule of thumb, not a published specification, so none is repeated here.
- 01That some light leakage is to be expected on dark backgrounds in dark rooms, the 150-lux and 70-lux inspection conditions, and the advice to compare with identical models and send an image: Dell, Troubleshooting light leakage or light bleeding on a Dell monitor — retrieved Sep 23, 2026.
- 02That leakage is judged with at least 150 lux and not in a dark room, that leakage seen in low light is a normal phenomenon, and the photograph-and-service-center route: ASUS, LCD screen light leakage judgement — retrieved Sep 23, 2026.
- 03Testing a monitor in a dark room, so dark areas can be assessed precisely, and warming the screen up first: EIZO, Monitor Test — retrieved Sep 23, 2026.