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"Should I buy a Plasma, LCD, Projection or CRT TV?"

From Ask Dave Taylor

Buying a television has never been more complicated than today, with four primary television technologies — plasma, projection, LCD or CRT — and a variety of different scan rates and resolutions, including HD, which has different meanings for different vendors.

More televised and DVD content is becoming available in High Definition (HD), digital broadcasting is becoming a requirement for terrestrial broadcasters, and more TVs are coming on the market to take advantage of these technologies. The result? It’s getting more difficult to stick with your old CRT TV, but hard to know which new technology will work best.

So you’re ready to consider upgrading. Good. Me too. But, which technology will it be?

Will it be plasma, with vivid colors, fast refresh and great contrast? This is the display most consumers drool over at their local big box store. The prices have been coming down over the years, so they’ve actually become an option for many of those potential purchasers.

The downside to plasma is high power consumption and relatively short life span. I have a 32” Sony CRT from 1996 that is only just now starting to show its age - the tuner is failing - so now I use the tuner in the VCR and pipe it to an input on the TV.

But that’s a completely different story…

Some tests have shown that the ability for a plasma display to show true black decreases by 13% over the first four weeks. Over a period of a few years this could show blacks as light grays in your image.

The high power consumption may not bother you if you don’t mind paying a bit more for your electric bill, but the real issue is the amount heat generated. In the spring of 2006 Philips paid to have components replaced due to heat related issues in 12,000 plasma TV’s that were already in people’s homes.

The heat comes from the million tiny fluorescent tubes on a heavy glass substrate that produce the image. This design is also part of the longevity issue. The high heat produced in a small area burns out the phosphors sooner than the phosphor on a traditional CRT. And, in tying everything together, this can also result in image burn-in especially on channels that display their logo continuously in the lower right corner.

Higher end plasma sets address some of these issues, but of course they are more expensive, so most people would be buying the less expensive versions that still have these problems.

So how about LCDs?

These are the most ubiquitous of the post-CRT technologies. They are much less expensive than plasma, but also tend not to have pictures that are as sharp or bright. Some manufacturers have started using LEDs instead of the standard fluorescent lamp to illuminate the display to improve the characteristics. Without a lamp to backlight the display, the LCDs would change but you would not be able to see them as they only filter light, they don’t emit it.

The other downside to LCD displays is that the pixels are relatively slow to change state. Fast moving objects such as a hockey puck or baseball bat get blurred where they might show more crisply on a plasma or good quality CRT. Among the attempts to overcome this particular limitation is to increase the refresh rate from 60Hz to 120Hz.

Projection on the rise

In my youth I had friends whose parents had some of the original projection TVs. My recollection is of large screens (maybe 60”), but rather washed out color. It didn’t really matter, as we would be watching old Dr. Who episodes of bad sci-fi.

Today, projection television has grown up and joined the fight for living room/media room space. The technology now produces much sharper, more vivid images that in previous years with deeper blacks that rival the CRT, and beat most of the plasma and LCD displays. This is the way to go for display sizes of 50 inches or greater.

There are several competing technologies in projections sets: Digital Light Processing (DLP), micro-LCD, and Liquid Crystal on Silicon (LCOS). DLP uses a couple million hinged micromirrors to reflect light (or not) through a color wheel. The micro-LCD passes light through three individual LCD screens (red, green, and blue) and uses mirrors to recombine the image for display. LCOS is similar to DLP in that light is reflected to form an image, but the light is reflected from a surface blocked by a liquid crystal filter, rather than redirected by mirrors.

The main drawback for any of the projection technologies is the lamp used as the light source. The typical metal halide projector lamp only lasts 1000 to 2000 hours and can cost several hundred dollars to replace. Longer life span lamps called ultra high performance (UHP) have recently come on the market that use mercury vapor instead of argon and have lifespans ranging from 3,000 to 10,000 hours.

As with LCD display, manufacturers are moving towards high intensity LED technology to replace lamps and get lifespans measured in years. Of course, that technology is not cheap, but prices should come down as they become more available in the next several years.

On the horizon we can look forward to SEDs.

What is SED?

SED is Surface-conduction Electron-emitter Display. These should be coming on the market in about 2008/2009. Japan will probably start seeing them by the end of 2007. They are a flat panel display, much like the LCD displays now, but have characteristics resembling that of the CRT for contrast and image quality. This comes from basis of the design: each pixel is basically a tiny CRT. It uses less energy than plasma since it’s easier to generate an electron beam (as a CRT does) than it is to excite photons in a gas (as the plasma display does).

Since there are no production display available for test, we need to take the manufacturers’ word that the displays have faster response than plasma or LCD, along with brighter colors and more vivid picture quality. There are no data yet for other performance or reliability factors.

So if you can hold out a few more years (and are willing to pay 50% more than a plasma goes for today), SED will make you the new cool guy on the block!

Whichever you choose, good luck and may your new TV be a wonderful addition to your household.

Source: “Should I buy a Plasma, LCD, Projection or CRT TV?” from the Ask Dave Taylor! Tech Support Blog

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