Even though it's possible next year will be the last year you'll be able to buy a plasma, they still represent the best picture quality value for televisions. Rumors about their fragility, especially when it comes to "burn in" still abound.
So what is burn in? Is it something to be concerned about? Can you fix it?
Cutting through the hype and fearmongering in 3...2...1...
What the what?
What is commonly called "burn-in" is better described as "image persistence" or "image retention." It results in a ghost of a bright image that was left onscreen too long. Technically, burn-in is a permanent form of image retention. Or, if you want to look at it the other way, image retention is a temporary version of burn-in. These distinctions are lost in current vernacular, but know that when most people talk about burn-in, they're really talking about image persistence/image retention. This is because when it comes to current-gen plasma TVs, actual burn-in is highly unlikely and extremely difficult.
How it happens
Image persistence is caused by the phosphors that make the image in a plasma TV continuing to glow after being overly excited.
Think of the phosphors in a plasma like kids. Once you get them riled up, it takes a bit for them to calm back down. Also like kids, as they age, they calm down much faster. As a plasma TV ages (after 100 hours or so), it becomes far more difficult to burn in.
When you first get a plasma home, depending on the brand, model, and how you set it up, it's possible you may see some image persistence. It might look something like this:
Or this, if you watch CNN:
Here's a typical cable news channel with its multiple tickers and banners:
Keep in mind, these are all illustrations of the problem created by me to demo the effect. The reality is more subtle.
So, yes, if you leave a static image onscreen for a few hours, it's going to stay there for a bit. It is NOT, however the end of the world.
It goes away
Here's the most important fact about image persistence: unless you're overtly negligent, it's easily reversible. With what magic, you ask? Easy, just watch TV. Yep, that's it. Just go back to your regularly scheduled programming (full-screen, non-letterboxed television) and it will go away by itself. Just due to being used, the phosphors will get back in line. Depending on the severity of the image persistence, it may take a few minutes or a few hours to go away.
I recently left ESPN running for 6 hours on a plasma I was reviewing, just to test this very issue. Sure enough, after the 6 hours there was a faint ghost of their sportsball ticker at the bottom of the screen (visible when viewing a black screen). Ten minutes of different content (i.e. without the ticker), and the image retention was gone.
Though it can be frightening to see image retention if you've just bought a new TV, don't panic. Watch something else for a bit. It should go away on its own with no further effort from you (and as I mentioned earlier, it becomes harder and harder to get image retention as the TV ages).
Part of the hysteria around image retention/image persistence is that for many years it was a bigger issue. As plasmas improved, the evil-sounding "menace," ahem, persisted as manufacturers and stores tried to push their customers into more expensive LCD televisions (which have their own issues).
Modern plasmas have better phosphors that are less likely to "burn" in the first place. They also include features designed to lessen the chance for image persistence or remove it if it occurs. An orbiter function moves the image around the screen by a few pixels. Hardly noticeable, but it minimizes some aspects of burn-in. Full white or rapidly changing colored patterns excite the phosphors evenly, greatly reducing the time it takes to remove the effects of image persistence.
LCD fanboys cry foul that these features are an admission by plasma TV manufacturers of a performance problem. To them, I say, what do you think 120 Hz, 240 Hz, and higher refresh rates are? They're an explicit attempt to "fix" the motion blur problem inherent in all LCDs. There's no such thing as a perfect display, folks; you've got to take some good with the bad.
Personally I wouldn't buy plasma or LCD, but that's just me. I'll stick with my 102-inch "TV." I say this not to boast, but to explain that I don't have a horse in this race. I'll review whatever technology comes my way and judge it on its own merits. I just can't stand misinformation, which explains pretty much everything I've written for CNET.
Oh, yeah, BTW, everything 'burns in'
CRTs had burn-in. OLEDs can burn-in. And believe it or not, even LCDs can "burn in." The mechanism for LCD "burn in" is different than with plasma/CRT/OLED, not least because LCDs don't have phosphors. They can exhibit image retention. It is less common, but still possible. Don't believe me? When was the last time you were at an airport? Find one of the departure/arrival screens. If they're not brand-new, I bet there's image persistence or burn-in regardless of the technology. I've seen this first hand with an LCD display recently, so it's not a myth.
OK, not everything has burn-in. DLP can't, at least not in the ways we're discussing. More likely, a mirror will stick on or off, causing that pixel to be white or (hopefully) black.
Work at it
Can burn-in be permanent? Yes. But you've got to work really hard at it. As in, you have to either be trying to burn an image in, or be forgetful enough to leave a single image on the screen for days. Because you have to be exceptionally careless to cause serious burn-in, plasma companies' warranties don't cover it. They also won't cover throwing things at the screen, dropping it in the pool, or lighting it on fire.
If you're worried about it, be aware that cable news channels are the worst, as are video games that have anything static onscreen (like a HUD, or stationary avatar). Letterboxed movies have the opposite effect, with the black letterboxes remaining dark while the movie image persists. Also, find on your plasma where the anti-image retention patterns/features are, and check out how they work.
There are plenty of reasons to choose plasma or LCD, but burn-in/image persistence shouldn't be one of them. It is much ado about nothing. OK, not nothing, as it's a real thing, it's just not the issue some people make it out to be.
Lots more info
HDGuru.com: Plasma TV 'burn-in': Fact or myth?
Plasma Display Coalition image retention tests
Imaging Science Foundation: Plasma TV performance (admittedly, sponsored by Pioneer)--PDF
Wikipedia: Screen burn-in
Got a question for Geoff? First, check out all the other articles he's written on topics like HDMI cables, LED LCD vs. plasma, active versus passive 3D, and more. Still have a question? Send him an e-mail! He won't tell you what TV to buy, but he might use your letter in a future article. You can also send him a message on Twitter @TechWriterGeoff or Google+.