High Definition TV

What you need to know about High Definition TV

High definition has been an exciting development in the world of television, but it has also been a confusing one.   Here at retra – the UK’s leading trade association for independent electrical retailers – we know only too well that customers can become baffled by the range of technology available.  So we have put together a simple guide, which we hope will help you make an informed decision.

One of the most common misconceptions when someone buys a HD ready or Full HD TV is that all they need do is switch it on to watch their favourite programmes in high definition.  This is not true!  HD simply means that your TV is capable of displaying a HD signal from a HD source such as a HD set top box or a HD DVD player.


A simple guide

The image that appears on your TV screen is made up of tiny picture dots called pixels.  These pixels are ordered in lines, which are squeezed tightly together.  Old fashioned ‘standard definition’ images used 576 lines to create a TV picture.   HDTV uses 720 or 1080 lines, which means the pictures are of much better quality.

When you go into a shop you will have a choice of 720p, 1080i and 1080p HDTVs.  The letters ‘p’ and ‘i’ refer to the different ways an image can be stored and transmitted (progressive or interlaced).  You can read more on these two methods toward the bottom of this article.

1080i and p are sometimes referred to as full HD – although out of the three options available, 1080p technically provides the clearest, sharpest images.

Do bear in mind however, that even if you buy a 1080i or 1080p TV you will only ever be able to view HD in the specification chosen by the broadcaster.  In the case of the terrestrial channels (BBC, ITV, Channel 4 and FIVE), they are likely to use 720p.  This is because they have limited access to TV airway space (known as spectrum) and 720p offers the most economical use of this space.

On the flip side, cable and satellite providers (Virgin Media, Sky etc) may elect to broadcast in the higher quality 1080 because they’re likely to have access to more of the spectrum.  It is also useful to note that many HD films are now recorded in 1080.

Making the most of your HDTV 

To ensure a HD signal reaches your HDTV, you need to access a service that broadcasts in HD, such as BT Vision, Freesat, Freeview, Sky or Virgin Media.

Blockbuster films are increasingly being made in HD and can be watched in HD if you have a Blu-ray DVD player or a special games console such as the Sony Playstation 3 or the Xbox 360 Elite.

Please also be aware that the cables you plug into your television will have an effect on how good your HD signal is transmitted.   To get the best quality signal, it is recommended that you use good quality HDMI cables.   

Extra technical bits

Interlaced Scanning: An interlaced video frame is made up of two scans, the first displaying every other picture line and the second filling the gaps left by the first.  This system was developed in the early days of television to provide a good picture quality (many picture lines) without using too much bandwidth (broadcasting capacity).

Progressive Scanning:
This system doesn’t split the video frame in to two separate fields as interlacing does, the image in drawn in sequence – from top to bottom – in a single scan.

Still have questions?

For more information on HD, please ask your local independent electrical retailer.  Don’t feel silly or awkward about asking questions…technology changes rapidly and many people find it confusing.   To find your nearest independent electrical retailer, click here