LCD display panels took a long time to graduate from those little things in notebook computers to the large centrepieces in our lounge rooms. But now they have done just that, with their only significant competition (at present) being the plasma TV.

Although all LCD TVs are based on the same technology, not all are the same and choosing carefully – and knowledgeably – will ensure that your TV keeps you happy for many years.

How an LCD works

To best understand how to choose wisely, it helps to know a little about how LCD TVs work. The LCD screen is formed of two parts. At the back is a panel that produces light. Unlike plasma, the active part (ie. the bit that changes colour) of an LCD TV doesn’t create light itself. Instead it controls the amount of light that can come through from the rear panel (which is called the ‘backlight’).

The LCD panel sits in front of that. It contains hundreds of thousands (in some cases more than six million!) independently controlled LCD crystals. Each of these can switch between being transparent and opaque, according to the electrical signals sent to them by the TV. So each of those tiny dots can either let light out or not, and each in turn has a red, green or blue colour ‘filter’ so that the light it does let through comes out the right colour.

Each group of three dots (one red, one blue and one green) is called a ‘pixel’, and is responsible for delivering an accurate colour at its place on the screen. All of them together make the picture.

All this sounds fine in theory, but in practice LCD panels cannot entirely block all the light, limiting how black the panel can go.