LCD TV buying guide

Expert advice on buying an LCD TV

PC World Staff (Good Gear Guide) on 26 February, 2009 15:50

We use LCD technology every day, from a simple alarm clock to the screen on your mobile phone. LCD television is the pinnacle of that technology; the end product of continual rigorous development and ingenious design. As each new generation rolls out of the world's LCD plants, the innovations are numerous and accompanied by 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, your budget and your lounge room.

How does LCD Work?

LCD stands for Liquid Crystal Display. Liquid Crystal is a substance that is in constant flux between solid and liquid states. The crystals are affected by heat and electrical current which makes them change their molecular structure. By default, a Liquid Crystal molecule is twisted and when electricity is applied to it, it untwists. This is useful because the effect of applying electricity can be accurately predicted. In LCD panels this molecular manipulation is used to turn pixels on and off.

An LCD panel is essentially two pieces of glass with Liquid Crystals and a matrix of electrodes sandwiched between them. Behind the panel is a series of lights which shine through the glass. The amount of light that passes and is seen by the viewer is controlled at each pixel. Every pixel has its own current and is given its own individual instructions. In a 1366x768 panel this is 1,049,088 pixels which all have to be given instructions at the same time up to 200 times per second. A 1080p panel has 2,073,600 pixels (1920x1080).

To create colour, each pixel has three sub-pixels. Each sub-pixel has a coloured filter over it in red, green or blue. From these three colours, any colour can be made. Black is made by completely untwisting the liquid crystal, which blocks any light coming through that pixel.

So, let's look at those numbers of pixels again. Keep in mind that each pixel has three sub-pixels and every sub-pixel needs its own instructions on what to do. This means that the processors in an LCD TV need to process 3,147,264 sub-pixels for 720p panels and an incredible 6,220,800 for 1080p. The difference between a good and bad LCD TV comes down to how well the video processors can accept a signal from a device and accurately interpret it across the panel.