Plasma burn-in explained

While the post-Boxing Day sales are behind us, we're still receiving a lot of email from readers agonizing over which TV to buy. There's also plenty of general questions concerning plasma vs. LCD, particularly those stemming from concerns over the issue of plasma burn-in. In a lot of cases, those concerns are stopping people from buying plasma.

Here's an email we received recently:

It's been noted that permanent plasma image retention is largely a thing of the past. However, in making that statement, does testing take into account usage such as running CNBC for 8 hours a day? I note the latest articles on burn-in are two-years-old.

I'm a skeptic and think something's an issue if the manufacturer refuses to warranty against the issue. Your thoughts on plasma and CNBC/Bloomberg-type viewing?

Ron from Austin

Well, Ron, the short answer is yes, burn-in or permanent image retention is largely a thing of the past (the key word here is "largely"). But the longer answer comes in several parts -- let's call them seven things you should know about plasma burn-in. Here goes:

1.What exactly is burn-in?

Plasma, like tube TVs and older CRT rear-projection televisions, is a phosphor-based screen technology. Due to uneven wear on the phosphors, if you let a static image sit on your screen for too long, that image can end up leaving a ghost of itself behind--it appears burned in to the screen. The biggest potential for burn-in occurs when you have a high-contrast image -- such as bright text set against a dark or black background -- because some pixels are turned on to the max while others nearby are completely turned off.

A good example is when you watch 4:3 aspect video on a widescreen display and have black bars framing the image on either side (the pillarbox effect). Also, you get black bars on the top and bottom of a picture when you watch 2.35:1 aspect movies on a 16:9 widescreen display (letterbox), which is the standard aspect ratio for all HDTVs. Then, of course, there are the news and stock tickers that run across the bottom of the screen when you watch various news channels, including Bloomberg, CNN, and ESPN.

Watch TV for a few hours with those images sitting there, and you could end up with an after-image of the bars or the ticker visible on other scenes. These after-images will be most evident when you're watching a brighter scene with the picture filling the whole screen.

2. Why is burn-in much less of an issue than it used to be?
For starters, many new plasmas include burn-in reduction features, such as screensavers and "pixel shifting" that help prevent burn-in. Some of these features are invisible to the viewer. For instance, newer Panasonic plasmas call it "pixel wobbling", while Pioneer Kuro plasmas have something called "pixel orbiting", but both do the same thing: They ever-so-slightly shift the image on the screen a pixel or two at set intervals. The shift is virtually unnoticeable. Many sets also have settings for treating burn-in should it occur. Often, this involves simply blasting the screen with a white image from several minutes to hours, which usually eradicates the ghost.

3. Are TV broadcasters and cable and satellite service providers doing their part to prevent burn-in?
Most TV broadcasters and cable and satellite service providers are quite aware that there are a lot of plasma owners out there, and they've taken steps to help you avoid burn-in. Some hardware, such as the upcoming TiVo DVR and Pioneer's plasma range, gives you the option of changing those pillarbox bars from black to grey, which keeps the pixels within the bar turned on and thus helps prevent burn-in.

In a lot of cases, broadcasters are also pretty good about moving things elements such as tickers or station logos around -- or removing them altogether -- to make sure static images don't linger too long. That said, some broadcasters seem to do a better job than others in this regard.

4. Are there some simple tips to follow to prevent burn-in?
CNET.com's video guru, senior editor David Katzmaier, says the potential for burn-in is greatest during the first 100 or so hours of use, "during which time you should keep contrast low (less than 50 percent) and avoid showing static images or letterbox bars on the screen for hours at a time". He personally has a three-year-old 50-inch plasma at home and notices that, after his wife watches the TV in the 4:3 mode (with black bars on either side of the image) for hours on end with no widescreen shows, he sometimes detects those after-images of the bars. But they quickly go away when he watches material that fills the whole screen (or he convinces her to use the grey bars).

"I just don't worry about it," he says. "Yeah, you can get some image retention once in a while if you look hard enough after hours of static images, but even then it's temporary, not permanent."

Thanks to some readers' feedback, we have a few other tips to help remove burn-in if it occurs. Reader gmccnet got good results by recording bright static on a VCR and playing it for 24 hours to almost completely remove the after-image. Alternatively, you can set the TV to an untuned analog station for the same effect -- just ensure the static covers the whole screen by using your Zoom control.

5. Will playing video games on a plasma lead to burn-in?
You might have heard somewhere along the line that playing video games on a plasma can lead to burn-in. The idea is that if some sort of fixed icon is always on the screen during a game, that image will end up ghosted onto your screen forever. Again, this just isn't a real risk these days, particularly if you follow the first 100-hours rule and mix a little TV watching in with your gaming.

6. When it comes to burn-in, are some TVs more prone to it than others?
When we review plasmas here at CNET, most of them -- including many budget models--don't experience any problems with burn-in. But if you want to be safe, a good rule is not to go too cheap when it comes to plasma. By no means am I insinuating that you should avoid all bargain models -- we haven't had an issue with burn-in with inexpensive plasmas -- but if you want to play it safe, spend a little extra dough.

7. So, if I have CNBC, CNN, ESPN, Fox News, or Bloomberg on all day long, is it a problem?
Look, if your primary use for your TV is watching stations that have stock or news tickers running on them 8 hours a day, buy an LCD. The reason you want a plasma is because you can get a big-screen model (50 inches or larger) that offers deeper blacks and better off-axis viewing for less money than an LCD. And if you're a day trader sitting at home, playing the markets during the day and watching movies at night, get a small LCD for daytime use and a big plasma for nighttime viewing. End of story.