Televisions buyer's guide
When you're buying a new TV, there are a lot of choices to be made about size, the type of screen technology and what added extras you want included.
Fortunately, that means the TV that's ideal for you almost certainly exists, but where do you start looking to find it?
The first and most obvious thing you should look for in a new TV is the screen size.
This is the diagonal measurement between two corners across the centre of the display.
Typical screen sizes start at 32 or 36 inches, and for a larger room go right up to 50 or more inches in diagonal.
How is the image on a TV displayed?
TV pictures are made up of thousands of dots or pixels, which are arranged in a grid on the screen.
The resolution is measured by describing the number of vertical columns of pixels by the number of horizontal rows.
Are all screens HD compatible?
Nearly every screen that you can buy now has a display resolution of 1920x1080 pixels, and carries the Full HD logo to show that it can match the highest definition of HD content, 1080p.
Some older TVs still use the HD Ready logo, which only guarantees that they can display the lower resolution 720p standard.
What types of display are there?
The way pixels are coloured in on screen varies from TV to TV.
You'll see most sets described as using one of four possible technologies: Plasma, LCD, LED and 3D. They're all subtly different.
The glass of a plasma TV screen is filled with tiny pockets of gas behind each pixel, which are superheated to produce light.
They shine through coloured filters to produce the image on screen – one of the benefits that a plasma screen offers is the accuracy of colour and saturation.
LCD TVs are illuminated by a powerful backlight, which shines through a series of liquid crystal display (LCD) filters that are dyed red, blue and green.
The crystals move to allow light through pixel-sized points to create a picture. There's no real difference in image quality between LCD and plasma screens these days, but LCDs are more popular because they tend to be better priced and more power efficient.
You'll see many newer screens described as using LED technology.
These are actually the same as LCD TV, but instead of using a cold cathode lamp for the backlight, they have lots of low power LEDs (light emitting diodes). Because LEDs are tiny compared to traditional bulbs and use less energy they also tend to be much slimmer so will save on space.
Only the latest screens that are branded with the 3D logo can be used to watch 3D films and TV shows.
There are lots of 3D films available on Blu-ray now, although you may need to upgrade your player to watch them, as well as computer consoles that have 3D games available. Sky also has 3D sports channels, and the BBC shows 3D broadcasts on its HD channels occasionally.
What else should I look for?
The two technical specifications which can be used to tell screens apart are the contrast ratio and refresh rate.
The contrast ratio tells you the difference in luminosity between the darkest colour a screen is capable of displaying and the brightest – in other words, the higher this ratio is, the darker the black and the whiter the whites, and the richer all the colours between should be.
The refresh rate is the number of times a picture on screen can change in a single second, measured in Hertz or Hz. The higher this number is, the smoother on-screen movements will generally be. Plasma TVs can be as fast as 600Hz, while a top spec LCD TV will have a refresh rate of 200Hz. An Active 3D TV is that they have to have a high refresh rate, so 2D action scenes look great on them too.
Glossary for other TV terms
Upscaling is a term that usually relates to taking standard definition videos – from a DVD, say – and using software algorithms to add extra pixels to create high definition images. It's not as good as watching something recorded in HD on a large screen but it's close. Some manufacturers have begun using the word to describe adding stereoscopic 3D effects to 2D sources – TVs capable of this have extra circuitry which analyses every frame and guesses what should be in the foreground and what should be further away, then tries to display that on a 3D screen.
High Definition Media Interface is the standard cable and connector which is used for transferring HD content between a set-top box and a TV screen. You can't watch HD movies using any other kind of cable. There are different versions of HDMI, though. The latest is HDMI 1.4, which adds extra bandwidth for 3D images.
Increasingly, TVs aren't just built with HDMI ports for getting sound and video to a screen. They also come with ethernet ports for connecting to the internet. Internet enabled TVs have lots of extra features, depending on the manufacturer, which range from special menu options to view YouTube shorts to full browsers and online movie rental services built in.
They aren't in mass production yet, but there are new TVs on the way that don't require the viewer to wear special glasses to see the 3D effect. Quite how good they'll be is uncertain right now, though, and it's likely that active shutter glasses will remain the best way to enjoy 3D for the time being.
Freeview is the digital broadcasting service that anyone can receive without paying a subscription fee. It carries over 50 channels including the BBC, ITV, Channel 4, Channel 5, Sky News, Film4 and Cbeebies. There are 24 digital radio stations broadcast via Freeview. In order to receive Freeview, you'll need a TV with a digital tuner or, if you have an older set, a special set-top box.
Freeview is the future. If you don't have a Freeview compatible TV or set-top box now, you need to get one. The old analogue broadcasting antennas which carry the standard five channels are being turned off as part of the digital switchover. The digital switchover is already complete in many areas, and the entire UK will have moved to digital-only TV broadcasts by the end of 2012.
Televisions features & videos
Watch the Tesco Technology and Entertainment summer showcase and discover the amazing gadgets available in-store and online