The low-down on high-definition

By Spencer Kelly
BBC Click presenter

Some things you need to know about High-Definition TV. Firstly, if you watch digital television, this does not mean that it is HD.

Two million HDTV sets are projected to sell in the UK in 2006

Digital TV describes how the picture is transmitted and received - through satellite, or a digital set-top box.

HDTV describes the quality of the picture, and the fact that it is very good.

The TV picture you normally watch is made up of pixels - 625 horizontal lines of small dots which make up the image.

If we were to zoom in on part of the picture you could see that under close scrutiny, there is not as much detail as you would first imagine.

An HDTV picture contains many more pixels, meaning a sharper picture, allowing us to see more detail in each scene.

The resolution of HDTV will be close to that of the films we see in cinemas, and that has got programme makers salivating over how great they can make their programmes look.

UK HDTV push

The World Cup is always an enormous worldwide draw to the TV screen, with millions and millions of fans watching however they can.

HDTV makers are keen to show off how much better this year's World Cup will look because it is the first to be filmed in HD.

Pandas, as filmed by the BBC's Planet Earth

The nature series Planet Earth was among the BBC's first HD shows

The BBC is using it to launch a trial HD channel, with more programmes coming along soon after.

Also, in the UK, Satellite broadcaster Sky is already broadcasting HD channels as part of a premium rate package.

The technology behind HDTV has been around for quite a while now, so why is there such a move to HD now?

Well, a big reason is because of the big screens we are now watching.

With an average screen size in the US of over 38 inches, the pictures are coming in for much closer scrutiny, and as we said earlier that shows up the lack of detail in standard definition images.

But is more detail necessarily a good thing? Standard definition TV hides a multitude of sins.

For example, if I am presenting Click and there's a hair on my shirt, you cannot see it. There is just not enough definition in the picture, unless the camera gets in really close.

Bigger budgets

But in an HD picture, all things like that will have to be tidied up. Sets, makeup and wardrobe will all need to stand up to closer scrutiny.

And that means more highly trained production staff, and more money spent on making everything look a whole level better.

Even a guy's stubble will need better makeup - in an HD image, you will be able to make out the individual hairs on the chin.

Even when the sets are nature itself, and the cast does not need makeup, TV camera operators will need to be operate their equipment more accurately than ever before because we will be able to tell if something is even slightly out of focus.

There are some other things you need to bear in mind before you race out and buy an HDTV.

Just because you own one does not mean everything will automatically look clearer.

The programmes you are watching have to be recorded in HD, after all the extra picture information needs to be there in the first place, before your shiny new TV can display it.

For example, not all the programmes in Sky's HD package are actually filmed in HD, so they will not really look any better.

All programme makers will need to spend some serious money on new high-def kit, including new cameras, if their productions are going to fully realise the quality of HDTV.