CRT HDTV - Plasma HDTV - LCD HDTV - DLP HDTV

High definition TV expands consumer choices from the traditional CRT and rear projection television sets. To these, now vastly improved types, it adds Plasma HDTV, LCD HDTV and DLP HDTV. As with most things in life, they all have their good and bad points.

CRT HDTV

Traditional CRT (Cathode Ray Tube) or 'direct view' works by shooting electrons at a screen. The electrons from the gun get pushed around by magnets, 'painting' the screen by illuminating lines of pixels (short for 'picture elements'). In the case of HDTV there are commonly 1,080 lines and the entire screen is formed from 1920 by 1280 pixels. There are lots of varieties, including those with only 720 lines and smaller numbers of pixels.

Newer HDTV style CRT models offer the same great pictures - deep, sharp blacks, excellent contrast, even richer and more realistic looking color, along with the enhanced resolution of HDTV. Better resolution translates to a sharper picture.

Those traditional strengths come with some trade offs. CRT tubes can only be made so thin before the edges of the picture become fuzzy. Though some current sets have shallow tubes, they are still deeper than flat panel TVs. Even shallow tubes are around 14" deep.

The largest screens are limited to about 38". And the larger the CRT, the heavier and bulkier they become. Most CRTs are at least 20" (51cm) deep and weigh up to 200lbs (91kg).

Plasma HDTV

One of the cleverest design ideas, plasma HDTV produces an image by passing a current through a gas held between two glass screens. The electrical current causes the gas to glow in a way similar to fluorescent tubes.

The screen size generally starts where CRTs leave off at 38", and can be as large as 62". Most are made in 'thin-profile' style, only a few inches deep. They're both lightweight and thin, making it possible to hang them on the wall. You can recreate the movie theater atmosphere and free up floor space.

But, although prices have fallen in the last year, they are still on the high side and quality is very mixed. Good sets will still cost upwards of $5,000 or more. Even then, the picture contrast is not always as good as you would expect especially considering the price tags on some Plasma HDTV's. In fact, the contrast on a Plasma HDTV is rarely as good as a high-quality CRT.

Newer model Plasma HDTV's have less problems with something called 'burn in'. Burn in results when a static image, such as the broadcaster' s logo, stays on the screen for long periods. The image then never fades. Burn in happens quite often on computer screens where the same image can be left on the screen for hours at a time. That is one reason screen savers were available in order to provide a non static image on the screen when not being used.

LCD HDTV - LCoS HDTV

Liquid Crystal Display (or Liquid Crystal on Silicon) HDTVs operate in much the same way as a laptop or flat panel computer monitor screen. It passes current through a series of rectangles.

Most LCD HDTV's suffer from the same problems as LCD computer monitors in as much that blacks are not black enough and contrast is not high enough. There is also the normal LCD screen problem in respect of limited viewing angle. To be able to get the best from a LCD HDTV or a flat screen computer monitor, you need to be able to sit directly in front of the screen. Trying to view the screen from any more than a few degrees either side makes it next to impossible to see anything on the screen.

However, advances have been made to overcome these problems but you will need to go for a more high end (read higher price) LCD HDTV. Barring the viewing angle problem, picture quality on a LCD HDTV can be truly outstanding and they do not suffer from burn in problems as do plasma screens.

DLP HDTV

Digital Light Processing or DLP HDTV is a rear projection technology that, in most commercial sets today, ranges in size from 40 inches to 80 inches. They frequently have replaceable lamps and offer excellent picture quality in a flat panel arrangement.

DLP HDTV's are often less costly than other HD sets and, with the micro-projector type, do not suffer from burn in problems.

Fortunately for those considering an HDTV purchase, prices have fallen over the last year and will continue on a downward trend. But do not wait too long. as by February 17, 2009 all broadcasters will discontinue analog TV broadcasts and switch completely to digital TV broadcasts. Sometime before that happens, prices are likely to peak.