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HolidayBuyer's Guide
TVs

Why isn't Freeview on LCD and plasmas as good as on my old TV?

Why doesn't the Freeview picture on LCD and plasma screens look as good as does on my old TV?

I keep looking to make the jump to a new TV, yet every time I look at them the standard Freeview picture is poor in comparison to my five-year-old Toshiba 32ZP18 TV.

Are there any LCD/plasma televisions that can match my current TV for standard definition material to make my 'jump' worthwhile, especially given that the majority of content is still standard definition?

Lee Graham

You've just asked the question that's on the mind of everyone looking to buy a new television. There are a couple of issues here, so we'll address them separately.

The first and most important point is that our existing broadcast infrastructure isn't set up for high-definition television. Both LCD and plasma screens use a video display system called 'progressive scan'. This differs from standard-definition television, which uses 'interlacing'.

Because CRT televisions all use interlacing to display their image, and the transmissions are set up to take advantage of this, everything broadcast uses interlaced video. This creates problems for the televisions that use the more modern progressive system.

Interlacing is a way to compress a TV signal so it's easier and less expensive to transmit. With an interlaced signal, instead of 25 frames per second being sent, each frame is split into two fields. These fields represent half of the total picture and are sent at a rate of 50 per second. This technique works brilliantly with CRT televisions, but because flat panels use progressive scan, where 25 complete frames are sent every second, the TVs need to restore the original information using some signal processing. This invariably degrades the image quality.

There is a further reason pictures look worse on flat screens. Traditional televisions show less detail than new high-definition ones. This means that to show a TV picture full-screen on a flat panel, the original image needs to be enlarged to fill the screen. This is like enlarging a photo on your computer -- the more you enlarge it, the more blurred and distorted it becomes.

A 720p LCD or plasma screen has a resolution of 1,366x768 pixels. A normal standard-definition PAL signal will have a resolution of about 720x576 pixels, so for this to be shown on a high-definition screen, the picture will need to be blown up. To do this requires complex electronic processing, which is costly to develop. The TVs with the best standard-definition picture will be the ones that have the best-quality electronics -- often the most expensive ones.

There is a further problem regarding Freeview. Put simply, there are too many channels compressed into the available space on Freeview -- while digital TV can produce a very good image, if it's too highly compressed the quality is severely degraded and will look poor when upscaled to a large screen. This is why DVDs look much better on your TV than Freeview ever will.

There aren't really any plasma or LCD screens on the market that will do as good a job with standard definition as your trusty Toshiba CRT. That said, plasma screens such as the Panasonic TH42PX600 and LCDs such as the Toshiba 32WLT68  and the Sony KDLV2000 do the best job we've seen with standard-definition pictures.

When it comes to high definition though, you can't beat an LCD or plasma, so if you're planning to get a next-generation games console or a Blu-ray or HD DVD player then you'll be blown away by the improvement in picture quality.