Old Computer Monitors

Most people who remember what computers were like way back in the eighties remember the old green-screen computer monitors which suffered from burn-in. When images were displayed over and over, the light slowly wore down the coating on the screen. Toolbars, the lines around the outside of a window or the lines of a spreadsheet which were almost always on screen would wear the screen out faster.  After several years a faint image of whatever was on the screen the most would be ‘burned-in’ and then was always on the screen, even when the monitor was turned off. Modern computer monitors don’t suffer from burn-in, but still tend to use ’screen savers’, which were originally intended to vary the image when the computer was not in use. They limited the amount of time that the same image was displayed continuously and preserved the screen. Now they just display cute images of cats or scenic vistas.

Plasma Screens

Modern plasma screens suffer from burn-in in two different ways. One is permanent, the other is temporary. If a screen is left on too long, the individual pixels can become charged in such a way that they glow slightly even when they’re not on. This effect is temporary, and fades after a few hours.

Plasma screens can also suffer from permanent burn-in, like the type of burn-in that occurred on old computer monitors, although it doesn’t happen as quickly or as severely as with the old monitors. Burn-in can occur on plasmas when the same image is displayed continuously for long periods of time. Ordinarily this isn’t a problem, because television images are constantly changing, not static images like the outline of a spreadsheet.

There are a few exceptions. When a television displays a computer game, very often the same images are displayed over and over. Sports shows often have a logo displayed in the same position on the screen, and news programs have logos or news tickers that appear in the same position over and over. If these channels are left on for long periods of time, it can result in burn-in.

When to Avoid Plasmas

Ordinarily, Plasma screens should work just fine for normal television. But, there are a few scenarios where an LCD would be a better choice. If you plan to use the screen as an oversize computer monitor, LCD is a better choice. Likewise, you should consider an LCD if you play a lot of video games. If you’re buying a screen for an office, or a sports bar, or a health club, where it’s likely that the same news or sports station will be played all-day every-day, then an LCD television is a better choice than plasma.

The situations under which Plasmas suffer from burn-in are few, and like every technology, the people who design them are working hard to eliminate difficulties like burn-in for newer generations of the product. I wouldn’t advise a typical television shopper to avoid Plasma, in fact I personally prefer the image on a plasma. Burn-in is something to consider, but it is only an issue depending on how you use the screen.

LCD

LCD screens are brighter than plasmas, are lighter, use less power and come in a wider range of sizes. LCDs generally start at about 19” in size and go up from there, with new models in ever-larger sizes coming out all the time.

LCDs are best for well-lit areas, like a living room with big bay windows. If the TV will be competing with direct sunlight or bright lighting, then LCD is probably the right choice. Because they are lighter, LCDs are easier to mount. LCDs come in smaller sizes, making them your only option if you want or need a smaller screen.

LCDs can have problems with ghosting, when an image doesn’t fade quickly enough off the screen. This results in fragments of an image that should no longer be on-screen being superimposed on what should be there, or a ‘ghost image’. It looks like a double-image or smeared image. Better LCDs are able to provide crisper images. The ability of an LCD to quickly release an image is measured in milliseconds and is referred to as the ‘Response Time’. A very good response time is 5 MS or below. Some computer monitors are rated as low as 2 MS, but most TVs have trouble getting below 5. 5-8 MS response time is acceptable, but anything above 8 may cause problems.

Here’s a simple test for how well a TV responds: watch a football game. Wait until the ball is kicked or passed and the camera moves quickly to follow the play. Look at the grass. The slower the response time, the more the grass will blur into a green mass and the longer the image will take to resolve once the camera stops moving.

The best type of television to watch on an LCD is anything shot in a studio. Talk shows, sitcoms and news programs are shot in controlled environments, with careful camera work. LCDs are going to show this type of programming best because the images will be optimized for a bright, clear display without any subtleties or surprises.

Plasma

Plasma screens are able to display dark, subtle scenes with more finesse and detail. They are more responsive, resulting in a clearer image. Plasmas aren’t available in smaller sizes. They are expensive to make, but the price gets more competitive the larger the screen due to economies of scale. Plasmas generally start at 40” and newer larger models come out all the time.

Because of the fact that LCDs and Plasmas are both available starting at 40”, that’s where the sweet spot in the pricing at the time of this writing for both types of screen. Go below 40” and you won’t save much money. Go above 42”, and you’ll see a significant price jump. It’s also the point where the highest available resolution screens begin to appear, so 40” screens are very competitive and where you see the best deals at the start of 2009.

Plasmas are better for watching movies and sports. This is because these images are difficult to display clearly, and the responsiveness and subtlety of a Plasma screen becomes apparent. Movies are often dark, and plasmas are better able to display really dark images. When Frodo is walking through Mordor, or a soldier is sneaking through foliage at night, a good TV will present that dark image as dark, but clear. LCDs aren’t as good at that, and will make the night look grey because everything is too bright, or else you will see forest, but no soldier because the fine details are indistinguishable. If you get frustrated because you can’t see what’s happening on the screen during a night scene, it’s because your television isn’t capable of producing a subtle enough image.

TVs compete with other sources of light. A good TV showing a dark image in a dark room will show up well, but the same TV showing the same image in a brightly lit room will be hard to see. Plasmas aren’t as bright as LCDs, and while Plasmas shine in the darkness, they can be overwhelmed by sunlight.

DLP-Projection

While not as common as LCD or Plasma, Digital Light Projection TVs are Rear-Projecting televisions. They have a projector mounted behind the screen. This means they are much thicker than Flat-Panel displays, but not nearly the depth of old CRT screens. They are very dim compared to both LCD and Plasma, but tend to come in larger sizes. If you can turn out all the lights and you want massive size, DLP may be the way to go. The newest units come with displays powered by LED lighting systems (light emitting diode) instead of regular light bulbs. LEDs will not dim over time or run the risk of burning out the way a bulb does.

Projector

A data projector, like you might use for a PowerPoint presentation, can also display video, although they usually do not include TV tuners. Resolution beyond 720 is still very expensive, but nothing beats filling an entire wall with an image from a projector for a large gathering. If you can turn out the lights and have a good screen or wall available, nothing beats the ‘price to screen size’ ratio of a projector.

The Questions to ask:

1. How much light is there where I want to place this TV?
2. How big do I need the screen to be? Can I afford the size of screen I want?
3. What kind of television will I be watching? News? Talk Shows? Sitcoms? Movies? Sports?

Some Tips:

1. The perfect spot for a Plasma is in a basement, where there are no large windows and the light is easily controlled
2. LCD is better in brighter areas, if it needs to be wall-mounted or if power consumption is an issue
3. If you can turn out the lights entirely and it needs to be huge, consider DLP
4. If you can turn out the lights entirely and it needs to be gigantic, consider a projector