Our Guide to High Definition and HDTVs

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It's been called the biggest revolution in TV since we all started watching in colour. High definition promises greater picture quality and clarity, and more detail, but how does it do this, and how can you get it for yourself?

TV pictures are displayed on screen a line at a time, in a process that repeats a number of times a second in order to give the illusion of a moving picture. On a regular telly, this process occurs 50 times a second, but the lines being drawn alternate on each loop - so first the odd numbers lines are drawn, then the even. This allows the display of 25 frames a second on your TV.

A "standard definition" - as it's now known - signal only has 576 horizontal lines and 768 vertical. High definition pictures can have up to 1,080 horizontal and 1,920 vertical, meaning over four times the level of detail in the same space as your regular picture.

HDTV can also use a technology known as "progressive scan" to display the whole picture in one cycle, meaning you get 50 frames per second playback - a feature which can also be seen on DVDs if you have the right TV - all HD Ready TVs support this feature, meaning your super-sharp, super-clear picture is also super-smooth.

What You Need to Watch HDTV

The first requirement of any high definition experience is a good high definition TV set. While Samsung is working on a way to get HDTV onto CRT sets, currently only some LCD, Plasma and rear projection sets, along with projectors, are capable of displaying the HD signal. One quick way to tell is to look for the logo pictured on the right - "HD Ready". A set displaying this logo on it has met a minimum standard allowing it to display HD pictures. A HD ready set must: Have a minimum of 720 vertical lines (enough for 720p output) Must accept HD input via component, HDMI or DVI The DVI or HDMI socket must support copy protection (HDCP) Extra connectivity is always a bonus - if you can get a TV with multiple SCART (for existing sources like non-HD consoles or TV receivers) and component / more than one HDMI connector (for things like Sky HD or high-def DVD players), you've got yourself a very good deal. Sometimes TVs are claimed HD Ready when they are not - always check with the retailer to confirm specs (most will display them on their website) before buying. For more information on the meaning of these terms, see our glossary. You can find a list of HD Ready sets in our HDTV buy guide, and we have picked our favourite set below, which is available at a good price but also has an excellent feature set.

Panasonic TH42PX60

from Comet

Integrated Freeview Tuner
Nicam Digital Stereo
HD Ready

High Definition TV Services

You can't get HD over an aerial, yet, you need to get it through your cable provider.

Sky HD

from Sky

Record two programmes at once without video
Hundreds of channels catering to all tastes
High definition movies, sport and documentaries
Half price for the first 3 months

720p: A slightly smaller high definition resolution which displays 1,280 x 720 pixels, running at 50 frames a second.
1080i / 1080p: A high definition resolution of 1,920 x 1,080 pixels. 1080i is "interlaced" showing 25 frames a second, 1080p is "progressive scan" showing 50 frames a second.
DVI: Digital Visual Interface - another method of connecting high defintion sources to your TV. Also commonly used as a method for connecting a computer to a flat-screen monitor.
HD Ready: The symbol signifying that a high definition television has passed a set of minimum specs for outputting HD content.
HDCP: High-Bandwidth Digital Copy Protection - a copy protection mechanism applied to DVI or HDMI connections to reduce the risk of content carried over the connection being copied to another source during playback.
HDMI: High Definition Multimedia Interface - the preferred method for connecting a HD source to the output, offering better copy protection (required for some future movie releases) and more capacity for picture transfer.
HDTV: High Definition Television - the future of TV. Crisper, sharper, more detailed images and a smoother picture.
Interlaced: A method of displaying the picture to the screen which draws the odd numbered horizontal lines on one cycle, followed by the even numbered on the next scan.
Progressive Scan: A method of displaying the picture where every horizontal line is drawn in sequence in a single scan down the screen, allowing for quicker refresh of the screen and potentially double the frame rate of an interlaced picture.
SDTV: Standard Definition Television - regular TV that we've all been watching before HD came along.