HDTV, LCD TV & Plasma TV UK

HDTV

High-Definition television (HDTV) means broadcast of television signals with a higher resolution than traditional formats (NTSC, SECAM, PAL) allow. Except for early analog formats in Europe and Japan, HDTV is broadcasted digitally, and therefore its introduction sometimes coincides with the introduction of digital television (DTV).

HDTV is defined as 1080 active lines, 16 x 9 aspect ratio in ITU-R BT.709. However, in the ATSC broadcast standard used in the United States and other countries, any ATSC resolution with 720 or more active lines is considered HDTV.

HDTV has at least twice the resolution of SDTV, thus allowing much more detail to be shown compared to analog television or regular DVD. In addition, the technical standards for broadcasting HDTV are also able to handle 16:9 aspect ratio pictures without using letterboxing, thus further increasing the effective resolution for such content.

Advantages of HDTV

1. All commercial HD is digital, so the signal will either deliver an excellent picture, a picture with noticeable pixelation, a series of still pictures, or no picture at all. You would never get a snowy or washed out image from a weak signal, effects from signal interference, such as herringbone patterns, or vertical rolling.

2. Most HD programming and films will be presented in the 16x9 proportioned, semi-widescreen format (though some films created in even wider ratios will still display "letterbox" bars on the top and bottom of even 16:9 sets.) Older films and programming that retain their 4:3 ratio display will be presented in a version of letterbox commonly called "pillar box", displaying bars on the right and left of 16:9 sets (rendering the term "fullscreen" a misnomer). Or, one can usually choose to enlarge the image to fill the screen, however this option will display a distorted, stretched-out picture.

3. The colours will generally look more realistic, due to their greater bandwidth.

4. The visual information is about 2-5 times more detailed overall. The gaps between scanning lines are smaller or invisible. Legacy TV content that was shot and preserved on 35 mm film can now be viewed at nearly the same resolution as that at which it was originally photographed.

5. Two new pre-recorded disc formats support HDTV resolutions. One is the currently available HD DVD, and the other is the as yet unreleased Blu-ray (expected June 2006). Players for both systems are expected to be backward-compatible with DVDs, however the two formats are not compatible with each other.

6. The increased clarity and detail make larger screen sizes more comfortable and pleasing to watch.

7. Dolby Digital 5.1 sound is broadcast along with standard HDTV video signals allowing full surround sound capabilities. (standard television signals broadcast basic stereo audio signals)

LCD TV

LCD stands for "liquid crystal display." Liquid crystal displays are everywhere in modern life, not just in TVs. Unless you live in a cabin in the wilderness, you can't get through a single day without running into, and probably yourself using, an LCD of one type or another.

LCDs are critical to many items of everyday life: wristwatches, stereos, car displays, hand calculators, instant-read thermometers and computer displays. LCDs in these items may not seem the same as TVs, but the exact same technology is used in all types of LCDs.

LCD TV sizes are quoted in different resolutions, such as 800x600, or 1280x1024. Those are pixel counts; the higher the count the sharper the picture will be at the same screen size, relative to a lower pixel count.

Plasma TV

Plasma screens are not a new idea; the basic technology has been around for more than 40 years. However, modern computers are the thing that make the complex displays of today's plasma TVs possible.

In a plasma TV, the computer at its heart lights, in the correct sequence and at the correct time, thousands or millions of tiny fluourescent spots ("pixels"). The lighting is done with electricity, and each pixel is red, green or blue. By combining pixels of these colours and varying their intensities, from which any colour can be made, the plasma TV reproduces the entire colour spectrum.

The reason it's called a "plasma" TV is that the light itself is a plasma--a gas with charged particles. A plasma can be controlled by introducing electricity, using the beam of electrons mentioned above

Plasma TVs are quoted in different resolutions, such as 800x600, or 1280x1024. Those are pixel counts; the higher the count the sharper the picture will be at the same screen size, relative to a lower pixel count.

The chief benefit, at least from most consumers' perspective, of a plasma TV is that it's possible to produce a very large screen that does not weigh thousands of pounds, as a conventional TV would. The screen is perfectly flat, which eliminates the distortions that come along with curvature. The secondary benefit is that the image is very bright and viewable from most angles.

Other advantages of plasma TVs include higher resolution than conventional TVs; no scan lines (the moving horizontal lines sometimes visible on conventional TVs); and a high degree of colour accuracy.