Plasma or LCD? There are other kinds of TVs out there, of course, from near-deceased CRT to rear projection, and the new but still tiny OLED format. But if you go to any electronics store today to buy a television, you'll probably end up deciding between these two dominant technologies.

Your salesman will likely mention many things. For example, he may tell you which TVs work better in dark or light rooms, their expected lifespan and warranty. It's possible he'll say, "Burn-in used to be a problem with plasmas, but it doesn't exist in the new models." Burn-in, of course, is what happens when you leave the same image on a plasma or CRT TV for a long time— eventually the phosphors will retain the image permanently, so you always see a ghost of it no matter what's onscreen. The two words he certainly won't mention are "image retention," the temporary ghosting effect that still dogs plasmas. Click Continue to read more about why that's a problem.

Image retention is different from burn-in because it is reversible. According to the Plasma Display Coalition, image retention is caused by accumulated electrical charge within pixel walls, not by phosphor burn-in. It looks just like burn-in, but it's not. Plasmas still have the potential for true burn-in, but you would have to work very hard these days to incur permanent damage to your television.

So forget burn-in. Let's talk about temporary image retention instead. The truth about image retention is that it's not that hard to cause, but that it takes a lot of time and electricity to make it go away. The Image Science Foundation did a study in 2005, sponsored by Pioneer Electronics, whose results are often quoted to show that burn-in is a myth or close to it.

Yet when you read the actual wording of the study, you can see that although image retention isn't permanent, it can take a long time to go away. Here's a direct quote from the study:

"After the 48-hour torture test, all three of the plasma TVs that were tested showed clearly visible images from the game menu, whereas none of the LCD or MD [micro-display] rear projection-based sets showed any image retention. However, after regular video material (a DVD movie set to continuously loop) was played through the sets for 24 hours, the image completely disappeared from all three plasmas, leaving no trace. Unlike early generation plasmas, where those type of images would not go away and could actually "burn" onto the screen, modern plasma TVs enjoy a combination of more robust screen materials and subtle image-shifting technologies that have rendered this former issue moot."

A couple of things to note here. First, LCDs were not affected at all by the "torture test." Next, to get rid of the image retention, researchers had to run the TV for 24 hours. It takes me a month to watch that much TV, and unlike LCDs, plasma screens don't "heal" these images when they're off. Houston, we've still got a problem.

Let's say you’re a gamer. At the end of a couple of intense weeks of Halo, you invite friends over for a movie. How embarrassing — your super-expensive TV has unsightly image retention. You played a movie beforehand to try to get rid of it, not realizing that you'll have to play 11 more before the ghosting disappears. That's more than a minor inconvenience.

You don't have to do a "torture test" on your plasma to see ghosting — just try using it to display your computer desktop for a few hours. Yes, the hard-drive icon will eventually disappear, but even minor image retention could take several hours to eliminate using your plasma set's "white wash" (almost all current plasma sets have one — an image retention-reducing screensaver). Plasma spokesmen (and fanboys) will tell you that image retention is uncommon, and will occur if you use your TV in an atypical manner. Their definition of atypical must be very broad: I see image retention at friends' houses and on commercial TVs all the time.

Why is image retention so important? Beyond just the obvious — it creates distracting ghost images — it's important because it's something the press almost completely ignores but should be a key ingredient in your decision-making process when you're standing in Best Buy choosing between a plasma or LCD TV. Yet if you go online to research the formats, all you'll read are articles that mention in passing that burn-in isn't a problem anymore.

For example, in a recent post called “Plasma TV Basics,” Gizmodo explained, “[burn-in is] now a nonissue when debating LCD vs. plasma.” When our colleague Charlie White tackled the plasma/LCD debate before the Superbowl he said, "Gone are the old problems with images burning into the screen." And when David Pogue had a conversation with a Best Buy salesman and annotated it with clarifications and corrections, he let this statement stand: “the traditional flaws of plasma (like burn-in)… have been largely eliminated.”

A trip to an online plasma-user forum like AVS or High Def forum shows that consumers are still talking about image retention. Why isn't anyone else?

Did you know that if you buy a plasma TV, you're supposed to spend the first 100 to 200 hours "breaking it in" like an uncomfortable pair of shoes? During this period, (around two months if you watch three hours every day), experts advise you to turn down the contrast ratio to less than 50%, turn the sidebars to gray if you're watching material with a 4:3 ratio, watch movies on zoom, and limit your gaming.

If you own a plasma, you've probably read this online or in an instruction manual. If you're a consumer trying to make the decision for the first time, chances are you won't know about it until after you purchase your plasma TV. And that could be disappointing — here's a brand new toy, and you have to gimp it just when you want to show it off.

Plasma TVs provide a great image. Many consumers will continue to buy plasmas for that reason, even if they know about the break-in period and the length of time it takes to get rid of image retention. But others, if they knew how high-maintenance plasmas can be, might decide to sacrifice a little image quality so they never have to worry about how long they display news scrolls and channel icons.

I'm not calling for a boycott, and I'm not an anti-plasma zealot, but I would like a more honest conversation about this phenomenon. Instead of, "Burn-in is a myth" or "Burn-in doesn't happen anymore," the discussion should shift to, "While burn in isn't a problem anymore, your plasma TV will be prone to image retention. You'll have to be careful about gaming, aspect ratios that don't match your TV, scrolling news bars, and using your TV as a computer monitor. If you do encounter ghosting, it could take a while to disappear. If you think you might lose sleep over this, you'll be better off with an LCD." It's a mouthful, but it's the truth.