Full HD or not full HD…

What's the difference?
Cue this feature, and an attempt to sort out this whole sorry mess once and for all. First, we should explain why a 1080-line TV might arguably perform better with high definition than a 720/768-line TV. First, so the argument goes, the extra pixel density of 1080-line screens arguably simply makes them able to show more detail than 720/768-line screens. Second - and this is perhaps more pertinent - 1080-line TVs theoretically let you show the 1080i HD format exactly as it arrives at the TV, whereas 720/768-line screens can only show 1080i HD sources after using video processing to 'downscale' the pictures to the TV's lower native resolution. And wherever there's such video processing going on, there's more potential for the image quality to be degraded.

This sounds fair enough so far, right? Maybe - but there are a number of reasons why writing 720/768-line TVs off just doesn't make sense. First, there are actually two high definition formats in common existence: 720p and 1080i. And since the 720p option actually uses 720 lines of picture, applying the same 'scaling processing' logic used by the 1080-line brigade you could argue that in fact 720/768-line TVs will do a cleaner job with 720p HD sources than 1080-line TVs!

However, it has to be said that at the moment there actually aren't any 720p HD sources available in the UK. At the last minute Sky announced that all of its HD channels would be shown in 1080i, rather than a mix of 720p and 1080i as had originally been suggested. And early word on HD-DVD and Blu-ray discs suggests that their HD films will be predominantly mastered in 1080 lines too.

This leaves as the biggest defence for 720/768-line TVs the fact that most quality TVs these days actually use very sophisticated picture processing systems to make pictures look better - so to suggest that 1080i HD sources will appear on 1080-line TVs 'purely', without any processing having been applied, just doesn't hold true.

Philips is particularly strong on this argument, with their chief TV engineer Danny Tack suggesting that the company's Pixel Plus processing engine can make 1080i HD sources look better on a 720/768-line TV than they would on a processing-free 1080-line TV. In other words, the quality of a TV's video processing is potentially far more important than its native resolution.

Bigger and smaller screens
One final point in support of 720/768-line TVs based on our experience of actually watching lots of them concerns screen size. Basically, we've found that on TVs smaller than 37in any benefits from native portrayals of HD pictures are so hard to see that they're pretty much negligible. So there's really no need to get a 32in or smaller TV with more than 720/768 lines.

But what of bigger screen sizes? Here, we have to say from our own experience that having a quality native 1080-line TV really can improve pictures with 1080i sources. And this seems borne out by 'science' as well as our eyes. As Toshiba's Ian Rea puts it: “1080 panels really come into their own with larger screen sizes. A 42in TV with a WXGA (1366x768) resolution will have around 1,049,088 pixels, which is the same as most 32in or 37in sets, but because the surface screen size is larger, the pixel pitch has to be bigger to fill the space.

“Image deterioration can occur due to the pixel pitches being larger to fill the screen space. In comparison, with a 1920x1080 Full HD resolution where the number of pixels is 2,073,600 (almost double that of WXGA), the pixel pitch is reduced to allow the larger quantity of pixels into the 42in screen size. With considerably more pixels at smaller pitch sizes the image quality delivered becomes far greater with heightened image detail.”

It's also fair to say that even if you take the arguments on board about picture processing being more important than native resolution, if a TV doesn't have to downscale a 1080i source, the burden on a TV's picture processing systems is reduced, potentially producing cleaner pictures.

So which should I buy?
As your head is probably reeling by now, let's try and sum everything up. The key point is that having a 1080-line screen can deliver a better 1080i HD performance provided:

a) the screen size is large enough to make the differences clearly visible and
b) the impact isn't negatively affected by aspects of a TV's picture processing system.

So that's that. But at the same time we're certainly not suggesting that large TVs that don't have a full HD resolution are a waste of space, since a 720/766-line TV with an excellent picture processing engine could out-perform a 1080-line TV with a poor picture processing engine.

Plus, of course, there's that ever so slightly key matter of price to consider. Strangely ignored in most debates about Full HD, it's a fact that for the moment at least, TVs with a full HD resolution tend to cost more than TVs with a 720/766-line resolution. In other words, the 1080-line TVs with their potential HD benefits are premium products for people willing to pay a bit more for that extra smidgin of quality.

And actually, when you take price into account you have to say that the whole furore around 'full HD' starts to look a bit silly. After all, in the music world everybody takes for granted that there are some people (the majority, in fact) who don't mind if a hi-fi sounds 'merely' good provided it's cheap; and there are some people who absolutely definitely have to get the best sound quality from their music sources no matter what the cost of the equipment needed to achieve such perfection. So why should the situation be any different with high definition TVs?

And let's finally not forget that no matter how much of a storm the press whips up about Full HD, we're only talking about degrees of excellence. In other words, anyone who sees HD running on a 720/768-line HD Ready TV should still have their socks blown off by the experience. All you're doing if you spend more on a quality large 1080i screen is creating the opportunity to have your socks blown that little bit further!