Monitor Dead Pixels, Backlight Bleed or IPS Glow? How to Tell Panel Defects Apart — Dead, Stuck & Hot Pixels, Bleed, Glow & Uniformity Diagnosis

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重點摘要

A dead pixel, a stuck pixel, backlight bleed and IPS glow look alike at first glance, but they have different causes and different answers. This guide explains how to tell them apart with full-screen colour tests and a simple viewing-angle check, so you can describe the fault accurately before deciding what to do next.

A new monitor that shows a strange spot, a glowing corner or an uneven patch can be worrying, especially when the fault only appears on certain screens. The first step is not to decide whether the monitor should be replaced. It is to identify exactly what kind of defect you are looking at. A dead pixel, a stuck pixel, backlight bleed, IPS glow and uneven grey shading all look similar in a casual glance, but they come from different parts of the panel and they lead to different decisions. This guide walks through each one, explains a test you can do at home, and shows how to record what you find so that a retailer or manufacturer can understand the problem without ambiguity.

How one pixel works

A liquid crystal display builds its picture from millions of tiny pixels. Each pixel is made up of three subpixels, one red, one green and one blue. By varying the brightness of those three subpixels, the panel can produce a wide range of colours. Most panel defects are failures at this very small scale, and that is why the definitions matter. Two faults that both look like a dot on the screen can be completely different problems once you know which subpixel is involved.

A dead pixel means a subpixel that never lights up at all. On any picture it appears as a black dot, because that part of the pixel contributes no light. It is easiest to see on a white or light-coloured background, where the surrounding pixels are bright and the dark point stands out. A dead subpixel stays dark on every colour, which is part of how you confirm it.

A stuck pixel means a subpixel that is locked in the on state. On a black background it shows up as a fixed dot of one colour, red, green or blue, depending on which subpixel is stuck. Unlike a dead pixel, a stuck pixel adds light where there should be none, so a dark screen reveals it best.

A hot pixel means the whole pixel is fully on, with all three subpixels lit. On a black background it appears as a white dot. It is less common than a single stuck subpixel, but the test is the same: a black screen exposes any pixel that is producing light when it should be dark.

The full-screen colour test

Guessing from a normal desktop wallpaper is unreliable. Icons, text and photographs hide small defects, and a defect that only affects one subpixel may be invisible on most pictures. A proper check uses a series of full-screen solid colours, one at a time: black, white, red, green, blue and mid-grey. Each colour has a job. White reveals dead subpixels. Black reveals stuck and hot pixels. A pure red screen reveals a faulty green or blue subpixel that would otherwise blend in, because the picture should be a perfectly even red; any dot of a different shade means one subpixel is not behaving. The same logic applies to the green and blue screens. Grey is useful for the larger-area problems described later.

Before you start, clean the screen carefully with a soft, dry microfibre cloth. Dust, a water mark or a tiny fibre on the surface is the most common false alarm, and it is easily mistaken for a dead pixel. If a spot moves or disappears when you wipe gently, it was never a panel defect. Also use your normal everyday brightness for the test. Turning brightness to maximum in a dark room will exaggerate every glow and leak, and the result will not reflect how the monitor looks during ordinary use. Test at the brightness you actually use, at your normal sitting distance.

Work through the colours slowly and note what you see for each one: which colour screen showed the fault, where on the screen it sits, whether it is at an edge or in the centre, and whether it changes when you move your head. That short record is far more useful than a vague description later, because it already separates the main categories before anyone else looks at the monitor.

Backlight bleed: light escaping at the edges

Backlight bleed happens in LCD panels when light from the backlight escapes around the edges or corners of the panel instead of passing evenly through the liquid crystal layer. It is most visible on a black screen in a dark room, and it typically appears as brighter patches hugging the frame, often strongest in the corners. Two features identify it. First, its position is fixed. It stays at the same edge or corner no matter where you sit. Second, it becomes more obvious as brightness rises, because a brighter backlight has more light available to leak. It does not move when you change your viewing angle, and it does not fade when you sit directly in front of the screen.

A small amount of edge light on a black screen in a dark room is a known characteristic of LCD construction rather than proof of damage, and judging it fairly means judging it under normal conditions. A test done at maximum brightness in a pitch-black room will make almost any LCD panel look worse than it does in daily use. If the bright patches are only visible in that extreme test and vanish at everyday brightness, they are unlikely to trouble normal viewing. If they remain obvious on dark scenes at normal brightness, the record you made during the colour test is what a retailer or manufacturer needs to assess it.

IPS glow: the viewing-angle test

IPS glow is different from bleed, and confusing the two is the single most common mistake in panel diagnosis. IPS panels show a silvery or pale haze over dark scenes when viewed from an angle. This is an optical characteristic of the IPS panel type itself, not a sign that the backlight is escaping. It appears on dark content, it is strongest when you look at the screen from off-centre, and it can look quite dramatic in a dark room.

The decisive test is to move. Sit directly in front of the screen and look at the dark picture, then slowly move your head to one side, or step to the side of the monitor, and watch what happens to the glow. IPS glow moves and changes as your viewing angle changes. A bright patch that follows your movement, shifts to a different part of the screen, or fades as you sit squarely in front is glow. Backlight bleed does the opposite: it stays pinned to the same edge or corner regardless of where you stand. That one difference, fixed versus moving, separates the two conditions more reliably than any photograph.

This matters because replacing a monitor for IPS glow may not change anything. Another panel of the same IPS type can show the same off-angle haze, since the effect comes from the panel technology rather than from a fault in one particular unit. If the glow disappears when you sit directly in front at normal brightness, it is usually something to understand and live with rather than a defect to chase. If a bright patch stays fixed at a corner from every angle, that is the pattern to report as possible bleed.

Uniformity, clouding and dirty screen effect

Not every panel problem is a single dot or an edge patch. Some panels show large-area unevenness: a grey screen that looks blotchy, a solid colour that is slightly brighter in one region, or a faint cloudy pattern spread across the display. This is generally described as poor uniformity or clouding, and it is best revealed by mid-grey and solid-colour screens rather than by black or white. Unlike bleed, it is not confined to the edges. Unlike glow, it does not move when you change viewing angle.

A related effect is dirty screen effect, where a panel shows faint irregular patches that become noticeable on large areas of even colour, such as a clear sky in a video or a plain background. It is worth knowing the name so you can describe it, but it is a broad topic of its own and is only mentioned here for identification. If your complaint is a single dot or a glowing corner, uniformity is not the right category, and mixing the categories only confuses the diagnosis.

Colour calibration is sometimes suggested as a fix for panel complaints, but it cannot repair any of the defects in this guide. Calibration adjusts how colours are reproduced; it cannot switch a dead subpixel back on, seal a leaking backlight or remove off-angle glow. If the fault is visible on a solid-colour test screen, it is a hardware characteristic of the panel, not a settings problem, and settings changes should not be expected to remove it.

The OLED boundary

Everything above describes LCD panels. OLED monitors work differently, because each pixel produces its own light and there is no backlight behind the panel at all. That means OLED screens cannot suffer backlight bleed or IPS glow, since there is no backlight to leak and no IPS layer to produce off-angle glow. Judging an OLED screen by LCD rules will lead to wrong conclusions.

What matters for OLED instead is near-black uniformity and the long-term behaviour of self-lit pixels, including the risk of image retention from static content shown for very long periods. Those are separate subjects with their own tests and are only noted here so that readers do not apply the LCD checklist to an OLED panel. If your monitor is OLED and shows uneven dark shading, describe it as near-black uniformity rather than bleed or glow.

Why a photograph can mislead

It is natural to photograph a glowing corner as evidence, and a photo is still worth taking as a record. But a phone camera does not see the way your eyes do. Automatic exposure brightens dark scenes, which exaggerates both bleed and glow, sometimes dramatically. A photo taken in a dark room can make a mild effect look severe, and a photo taken at a different angle can turn glow into something that looks like bleed. For that reason, a single photograph should never be the sole basis for judging severity. The reliable standard is what your eyes see at everyday brightness, at your normal sitting distance, from your normal seating position, combined with the viewing-angle test. Use the photograph as a supplement to your written record, not as a replacement for it.

Stuck pixels and the folk attempts: what to know first

For a stuck pixel, two folk attempts are commonly mentioned online. One is to display rapidly changing colours over the affected area for a period of time. The other is to press the spot extremely gently through a soft cloth. Both are widely discussed attempts, and both must be understood for what they are: unproven tries with no guarantee of success. Neither is a repair method, and neither should be presented as a fix that will work. The colour-cycling attempt costs nothing but time, yet it may simply do nothing. The pressing attempt carries a real risk: pressing too hard can damage neighbouring pixels and create additional dead pixels, turning one small fault into a worse one. Anyone who tries it should use only the lightest touch through a soft cloth, stop immediately if there is no change, and accept that failure is the likely outcome.

Dead pixels have no equivalent folk remedy, and this guide deliberately offers none. A subpixel that never lights up cannot be coaxed back by pressing or by flashing colours, and advice that claims otherwise is misleading. If a dead pixel is the confirmed fault, the honest options are the decision process in the next section, not a home remedy.

Deciding what to do next

A clear record makes the next step much easier. Before contacting anyone, write down the full test result: which colour screens showed the fault, the exact position on the screen, whether it sits at an edge or in the centre, and whether it moved when you changed viewing angle. Note the brightness you used and whether the fault is visible during normal use or only in a dark-room test. That record lets a retailer or manufacturer assess the case without a second round of questions.

The route then depends on timing and on the terms that apply to your purchase. Within a retailer's return or exchange period, the question goes to the shop you bought from, with your proof of purchase. After that period, the question becomes a manufacturer warranty matter. Warranty and return policies differ between brands, models and sales channels, and they change over time, so this guide deliberately does not state any particular threshold or brand policy. The only reliable basis is the policy published by your purchase channel and by the manufacturer at the time you make the claim, and you should check those current terms before assuming what is covered.

If the monitor is out of warranty, the choice is between accepting the fault and replacing the monitor. That judgement depends on how visible the fault is during your real daily use, not on how it looks in a dark-room test. A single dead subpixel that is invisible at normal distance during ordinary work may be easy to live with, while a bright fixed patch that intrudes on every dark scene may justify replacement. A diagnostic check at our shop follows our published three-tier fee range of HK$400–2,800, and we can help you confirm which category your panel fault falls into before you decide.

Common misunderstandings

A glowing corner does not automatically mean the monitor is broken. IPS glow is a normal optical characteristic of IPS panels, and it must be separated from bleed with the viewing-angle test before any conclusion is drawn.

A clean white screen does not prove there are no bad pixels. A single faulty subpixel may only reveal itself on the matching pure colour screen, which is why the full series of colours matters.

A severe result at maximum brightness in a dark room does not equal a severe fault in daily use. Tests should reflect everyday conditions.

A photograph does not prove severity on its own. Camera exposure exaggerates glow and bleed, so the eye-level test at normal brightness is the standard.

Pressing a stuck pixel does not guarantee a cure. It may do nothing, and pressing too hard can damage more pixels.

Frequently asked questions

How can I tell a dead pixel from a stuck pixel?

Use full-screen black and white screens. A dead subpixel shows as a black dot on white, because it never lights up. A stuck subpixel shows as a fixed coloured dot on black, because it is locked on. A hot pixel shows as a white dot on black, because the whole pixel is fully on.

What is the quickest way to separate bleed from glow?

Move your head. Glow shifts and changes with viewing angle, while bleed stays fixed at the same edge or corner from every angle. That single test is more reliable than a photograph.

Should I test at maximum brightness?

No. Test at your normal everyday brightness. Maximum brightness in a dark room exaggerates both bleed and glow and produces a result that does not match daily viewing.

Can colour calibration fix a dead pixel or bleed?

No. Calibration changes colour reproduction. It cannot revive a dead subpixel, seal backlight leakage or remove off-angle glow.

Does a glowing corner mean my monitor is faulty?

Not necessarily. If the glow moves with viewing angle and fades when you sit directly in front, it matches IPS glow, which is a characteristic of IPS panels. A bright patch fixed at a corner from all angles matches bleed instead.

My monitor is OLED and shows uneven dark shading. Is that bleed?

No. OLED panels have no backlight, so they cannot have backlight bleed or IPS glow. Uneven dark shading on OLED is described as near-black uniformity, which is a different subject.

Is there a home fix for a dead pixel?

No reliable one is offered in this guide. Folk attempts discussed for stuck pixels carry no guarantee, and pressing carries a risk of damaging more pixels. A confirmed dead pixel is a matter for the warranty and replacement decision process described above.

Where to get help

If you have run the full colour test and still cannot classify what you see, bring the monitor and your written test record to our shop at Room 1209, Dali Plaza, Shek Mun. You can also reach us by phone on 2186 8010 or by WhatsApp on 6558 6806. Diagnosis is carried out at the shop, and we do not offer a home-visit service. A clear record of which colour screens showed the fault, where it sits and whether it moved with viewing angle will help us confirm the category quickly and advise you on the sensible next step.