The Principles
The obvious difference between a plasma TV and a conventional set is the size. While a CRT (Cathode Ray Tube) TV has to be up to two feet deep, a plasma model can be mere inches in depth.
This is what gives plasma sets their space-age look. You can hang them on a wall, or mount them on an elegant stand, and they will actually enhance your living room.
Plasmas can also have much bigger screens, and prices have dropped sharply as the technology has matured. Prices can now be as low as £1,500 for an award-winning 50-inch set and are still falling.
Basic technology
The technology employed to allow these slimline dimensions and large screen sizes is complex, but it boils down to an array of gas-filled chambers in the screen. The gas in these chambers is inert (think back to those chemistry lessons you thought you’d never need again and you might dredge up the names ‘xenon’ and ‘neon’), but they can be used to create dots of red, green and blue light, in enough combinations to create many millions of colours and make up a TV picture.
Pros
• Most plasma screens are compatible with high-definition signals – these are now available as broadcasts from Sky and Telewest and from the new high-definition disc formats, Blu-ray and HD DVD.
• Plasma screen sizes go up to 60 inches (measured diagonally), way bigger than you could get from a CRT set, and the bigger sizes are ideal for getting the most out of high-def material.
• Perfectly flat screens – many CRT sets offer this as well, but all plasma sets are flat, meaning there is no distortion of images at the edges of the screen.
Cons
• They are susceptible to ‘screen burn’ where an image (especially a channel logo) can become burned into the screen if displayed for too long.
• Contrast (the difference in brightness between the dark and light areas of a picture) can be poor on some models.
Top tips for buying a plasma screen
• Ensure that a screen can handle high-definition images (look for the HD Ready badge).
• Check the contrast and brightness – these are traditional weak spots in a plasma, but advances in the technology mean you do not have to put up with a washed-out picture any more.
• Check the inputs – make sure there will be enough sockets, especially the new HDMI connections, to hook up all your other equipment.
• Check for speakers! Not all plasma sets have their own speakers, so you may need to buy a separate sound system unless you only watch silent movies.
• Look at the ‘response time’, the amount of time it takes a pixel to go from inactive, to active and back to inactive. Slow response times result in blurred images, especially when trying to handle fast movement. The lower the figure quoted (in milliseconds) the better.
• Beware of ultra-cheap sets that may be technically inferior.
‘HD ready’ plasma sets
Plasma sets are ideal for taking advantage of high-definition broadcasts, and the TV industry has taken the guesswork out of buying a high-definition capable set by introducing the ‘HD ready’ badge. Any TV that sports this badge is guaranteed to be able to display a high-definition signal.
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Glossary
CRT – Cathode Ray Tube. The conventional TV format, where electrons are fired at a phosphor-coated screen to generate images
High-definition – a superior delivery format for TV that presents more lines of detail, resulting in a much sharper, more detailed image
DVI – Digital Visual Interface, a digital video-only input or output
HDCP – High-bandwidth Digital Copy Protection. Intended to stop us from running off high-quality pirate copies of HD programming
HDMI – High Definition Multimedia Input – also known as the ‘digital Scart’, it carries video and audio signals in digital form
Phosphor – A substance that generates light when excited by an energy source
Plasma – a state of being distinct from gas, where the electrical characteristics of a gas have been changed due to the application of heat or other energy source
Response time - The time it takes for a cell to go from inactive to active and back to inactive. The lower the figure the better
