Plasma TV buying guide
- — 25 October, 2007 15:51
- How does plasma work?
- Does size matter?
- Is the native resolution really high definition?
- What is 1080p and do you need it?
- What do you need to connect?
- Watching TV
Since the 1990s, the word plasma has been synonymous with flat panel television. The first of the plasma displays were ultra-expensive and subject to all kinds of burn-in problems and short life spans. As each new generation rolls out of the world's plasma plants, the innovations have become numerous and accompanied with a leap in quality and capability. This poses a unique problem for consumers that they have never really had to face before when buying a television. The market is flooded with choice, and with the high price of flat panel televisions, it is hard to make the right decision with confidence. The purpose of this Buying Guide is to show you what to look out for so that you will take home the panel that best suits your needs, budget and lounge room.
How does plasma work?
Plasma works pretty much the same way as an LCD television. Two layers of glass and a matrix of electrodes are used to heat small chambers of gas -- one for each sub-pixel. LCD panels need the back light to create an image because Liquid Crystals can't create light. However, plasmas don't have a back light because the process of charging a sub-pixel creates light. This is why blacks look better on plasmas. On LCDs they tend to turn a little grey because of the backlight.
Each sub-pixel has a gas chamber and the gas inside reacts to an electrical current and emits Ultra-Violet light. This light then hits the coloured phosphorous layer. Like LCD, each sub-pixel has either a red, green or blue phosphorous layer. When the UV light hits the phosphors they become excited and emit their specific coloured light. The level of UV light will determine the intensity of a particular colour so the voltage being pumped into the gas chamber needs to be strictly regulated.
What people call "burn in" is caused by dead phosphors that are stuck in the one state and cannot change. This is not that common any more. What people see these days is actually called "image retention" or "phosphor retention". This is where the phosphors remain excited because they are not properly discharged between frames and so retain the information they were previously given. This can be easily corrected by discharging all the phosphors with a completely white screen for an hour or so.