Two different things with similar names
People use “burn-in” for any faint leftover image. In practice, two different effects get lumped together:
- Temporary image retention, sometimes called a ghost image or image persistence, where a faint outline of a previous picture remains for a while and then fades.
- Permanent image retention, usually called burn-in, where the screen has worn unevenly and the outline no longer goes away.
They look similar at first, which is why a temporary ghost can cause unnecessary worry. The causes are thought to be different, though, and the explanations below are general; exact behavior varies by product.
Temporary retention on LCDs
On an LCD, each subpixel changes how much light a layer of liquid crystals lets through, as described in the article on how liquid crystals control light. A subpixel that has been held at the same setting for a long time can take a while to return to its normal state afterward. One commonly suggested cause is that electrical charge builds up in the layers and takes time to dissipate. When the picture changes, the previous pattern briefly remains as a faint difference in brightness or color.
The effect is usually most visible on a mid-gray or uniform picture, where small differences show up. In many cases it fades after a few minutes or hours of different content, or after the screen is switched off for a while. Showing a moving or varied picture generally helps it clear, although the time varies.
Fixed images held for a very long time are the typical trigger, such as a static desktop, a test chart or a menu left on screen. Rarely, on some LCDs, persistence may last longer or may not fully clear; this is less common than on emissive screens.
Burn-in on OLED screens
An OLED panel does not use a backlight. Each subpixel is a tiny organic light emitter, and the light output of an emitter gradually declines as it is used, a process covered in the article on organic light emitters and in the account of panel aging. Different subpixels wear at different rates, depending on how much they are used and how hard they are driven.
If a bright, fixed element sits in the same place for very long stretches, the emitters beneath it are used more than their neighbors, and they dim a little faster. When the picture changes, the more heavily used area appears slightly dimmer, or tinted, than the surroundings. That uneven wear is permanent, because it comes from used-up emitter material rather than a temporary state.
Several factors are generally thought to raise the risk:
- Static elements such as logos, channel bugs, taskbars, scoreboards, game HUDs and menus.
- High brightness for those elements, since driving an emitter harder tends to speed its wear.
- Long continuous hours with the same layout.
- Blue emitters. Different colors may age at different rates, so uneven wear can also show as a color tint.
Screens also show a temporary version on OLED. A short-lived ghost can appear after a bright static image and fade, which is separate from permanent wear.
How common is it?
It depends heavily on the way a screen is used. Someone watching varied video content on an OLED television for a few hours a day is generally in a different position from someone who keeps a news channel with a fixed ticker on for most of the day. Makers have added various countermeasures over time, such as subtle pixel shifting, brightness limiting of static content, and periodic refresh routines. How well they work differs by product, and none can be guaranteed to prevent wear completely.
Because it is hard to predict, any figure like “this many hours will cause burn-in” would be a guess. It is more helpful to think in terms of habits and risk factors.
Telling them apart
A few simple observations help:
- Does it fade? Switch to varied content, or turn the screen off for a while. If it fades, it was temporary.
- Does it look the same on a gray screen? Permanent wear shows up as a consistent patch on a plain background. Test patterns of uniform gray or color make this easy to see.
- Does it follow the content you left on? A ghost that matches a recently displayed static item is a clue.
- Is it visible on bright content? Very mild retention may appear only on a flat gray or a dark picture and be invisible during ordinary viewing.
A related but different issue is uneven lighting from the manufacturing process, which is present from the start and described in the articles on backlight bleed and screen uniformity. If a patch was there on day one and does not change, it is probably not retention.
Reducing the risk
None of these steps are guarantees, but they are widely suggested:
- Vary what the screen shows; avoid leaving the same image on for hours.
- Lower brightness where possible, especially for static content.
- Use a screen saver or let the display sleep when you step away.
- On OLEDs, hide taskbars and toolbars where convenient, and consider dark mode, which can reduce wear in some interface designs, as the discussion of dark mode notes. Whether it helps depends on the content.
- Allow built-in maintenance routines to run; some screens perform them when in standby, which is one reason to avoid cutting the power every time.
- For digital signage, rotate layouts, vary the position of fixed elements and use moving content where possible. The ideas under signage content and continuous operation apply here, as do the standby behaviors of always-on displays, where static content running for long hours is a particular concern.
If it happens
Temporary retention generally goes away on its own. Permanent burn-in cannot be reversed by the user. Some makers cover it in warranty terms and some explicitly exclude it, so it is worth checking the terms of your product. Software tools that flash colors claim to fix burn-in, but since it comes from used emitters, there is no good reason to expect them to reverse it, and extended use of high-brightness patterns could add wear. A mild case that is only visible on a uniform gray background can often be ignored in daily use.