The Hindu Business Line : Tech-talk for dummies!

Televisions in general consist of thousands of small `picture elements', abbreviated as pixels. With any colour television, a bundle of three separate colours comprise one pixel, usually red, green and yellow. By controlling the level of each colour, all of the other colours of the spectrum can be produced in each pixel. Individual pixels blur into each other and the illusion of motion is created as they change colour.

In a plasma TV, the individual pixels are made from three tiny containers of an inert gas such as neon or xenon. There are literally hundreds of thousands of these tiny tubes on an average plasma TV screen.

All of these individual pixels are sandwiched between two electrically charged plates. Remember that plasma glows when exposed to an electrical current. A computer processing unit receives signals from a cable or broadcast antenna which tells it how to reassemble the entire picture hundreds of times per second. This means the colours are usually deeper and richer.

The main drawback of a plasma TV system is its vulnerability to damage. If a hard object strikes the screen, hundreds of individual gas-filled tubes instantly lose their ability to glow. Replacing all of those elements is a time-consuming and expensive process, if it can be done at all.

Owners of plasma TV systems should always consider purchasing insurance and extended warranties, since the most common fix appears to be total replacement of the screen. Because the gas forming the plasma can leak or become less reactive to electrical charges; plasma TV systems do have a limited shelf life.

It may take several years before there is a noticeable change in picture quality, but the cumulative effects are similar to what happens in neon and fluorescent lighting; eventually, the gas inside the tube will begin to flicker instead of burning steadily.

LCD TVs use millions of crystals, which are suspended in a liquid that is sandwiched between transparent panels. Behind this sandwich is a bright fluorescent light. The crystals are instructed to either let the light pass through or not. Colour filters are used to determine colours.

Screen size: Both LCD TVs and plasma TVs are thin. In screen size, plasmas usually run larger though they don't usually come in smaller sizes, which is sometimes needed.

Viewing angle: Plasma has a wider viewing angle. The viewing angle is how far off to the side you can sit and still see the picture clearly. You may have people sitting at various places all around the room. Historically, the plasma vs LCD battle has been won by plasma TVs in this category.

However, LCD TVs have made tremendous strides in this area of late. But many people may tell you that the 170° field of vision claimed by some LCD manufacturers simply isn't realistic. You may be able to see what's happening at that angle, but it isn't the same as sitting more head on. Reports from some owners of newer, top-of-the-line LCD TVs, however, say that the 170° claim is accurate.

Drawbacks and advantages: Plasma sometimes suffer from a `burn in' effect. LCD TVs are sometimes susceptible to a delay that causes the outline of figures or objects to appear jagged.

LCD TVs are renowned for sharp pictures and vibrant colours. Plasma TVs are known for a wide range of colours and accurate colour reproduction.

LCD TVs are said to do slightly better in bright-light conditions.

Plasma TVs generally produce very black blacks whereas an LCD TV will produce a very dark charcoal grey.

Plasma TVs, technically, are said to have greater contrast levels.

R. Ravikumar

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