Do I need a TV with 1080i or 1080p?

I want to buy a new TV and I've heard a lot about 1080i and 1080p -- which sort of screen should I go for?

Sarah

There's a lot of confusion about 1080i and 1080p. First of all, I'll explain what both are, and how this confusion arises.

There are two parts to these hi-def numbers. The first is the number itself, which refers to the number of horizontal lines that make up the image. Standard-definition TV consists of around 575 visible lines, while high-definition TV has either 720 or 1,080 lines. The second part is the letter, which denotes whether the signal is interlaced or progressively scanned.

In standard-definition TV, each picture frame -- of which there are 25 per second -- is composed of two fields. Each of these fields contains half the information that makes up the whole picture. On a traditional CRT, these two fields are shown one after the other, very quickly. This happens at a rate so fast your eye can't tell, so you see one solid image. This is known as interlacing.

This technique is well suited to broadcasting because it saves bandwidth, and CRTs handle the signal so well you can barely tell it's even happening. Plasmas and LCD screens don't work in the same way -- instead, they show whole frames successively. This is known as progressive scan. Normal TV signals must be converted before they can be displayed.

The fact that flat panels don't use interlacing means that there is no such thing as a 1080i LCD or plasma. Instead, these screens will offer a native resolution of either 720p or 1080p. If a flat-screen TV is touted as 1080i, it really just means it's a 720p TV that converts a 1,080 line interlaced signal into a progressively scanned 720 line one. To have the 'HD Ready' label, all TVs must support 720p and accept input signals of 1080i.

There have been a number of TVs that have 1080p panels -- ones with a native resolution of 1,900x1,080 pixels -- but couldn't support 1080p, so would down-convert it internally and then scale it back up for display. This is every bit as shoddy as it sounds, and TVs doing this should be avoided at all costs.

All of this makes the choice between 1080i and 1080p simpler, because you can decide which TV best suits your viewing habits.

If you watch a lot of normal TV and want to watch DVDs and possibly some high-definition TV via satellite or cable, then you can easily manage with a 720p set, especially if you are looking to buy a TV under 37 inches. It's doubtful that Sky and other broadcasters will ever send 1080p signals over the air -- it's quite simply uneconomical to do so.

If you play a lot of games on a PS3 or Xbox 360, like watching movies on either HD DVD or Blu-ray and need a screen size of more than 37 inches, then you're probably going to want to get a 1080p TV. Although it's not essential, you are more likely to see the benefit of a 1080p TV with this kind of material.