LED, LCD and plasma TV: Which television LED TV

What is LED technology in TVs?

LEDs (light-emitting diodes) have been around for decades, but their introduction into HD TV design and availability on the high street is a fairly recent development.

LED televisions are basically LCD TVs with one crucial difference – the handful of traditional back light lamps that illuminate the screen have been replaced by hundreds of smaller LEDs.

To give an LED TV its full name is more of a mouthful: LED-lit LCD. LED TVs still employ standard LCD TV technology; light from behind the screen is shone through the television screen's matrix of tiny coloured liquid crystal cells. Signals control each cell, letting varying amounts of colour through, and a picture is built up.

Keep an eye on our LCD and plasma TVs reviews to read full reviews of new LED TVs as we test them

Who makes LED TVs?

Following on from Sony and Samsung in 2008 and 2009, most of the major television manufacturers have now launched an LED TV range. 

The downside at the moment is common to any new technology – a hefty price tag. The benefits on the other hand are apparently threefold: LED TVs are slimmer, more energy-efficient, and picture quality, to date, has generally been impressive.

Do LED TV pictures look better?

In theory the use of LED back lighting should deliver an improved contrast between bright and dark elements of a picture. 

It's still early days, but the few LED TVs we've tested have fared well in our viewing panel assessments and final reckonings.

With a handful of exceptions, we found the LED TV pictures vibrant, sharp, detailed and oozing with depth, though the viewing angle is poor (a common problem on LCD TVs that the new back lighting doesn’t appear to have resolved).

Whether this picture quality success can be set purely at the door of LED back lighting is a moot point. All the LED TVs we’ve tested are higher end (and very expensive) models, so we would expect a loftier performance – but nevertheless the signs are promising.

LED TVs are slimmer than LCD TVs or plasma TVs

There are basically two types of LED TVs - Edge LED TVs and backlit LED TVs. 

Edge models are simply those with the LED lighting placed around the the edge of the screen. Without the traditional bulky lamps at the back of the TV, Edge LED models can be designed to be incredibly slim. For instance, the Sony KDL-40ZX1 is a mere 9.9mm thick. 

However, the same TV suffers from an uneven backlighting effect, especially in the corners of the screen. This is a problem Samsung seems to have cracked with its UE40B7020 and UE55B7020 models. Both Edge LED models manage to deliver an evenly lit screen thanks to some clever light diffusion technology. 

Thicker LED panels, such as Samsung's 2008 LED TVs, or the LE700 and LE600 from Sharp, are typically illuminated by LEDs dotted over the rear of the panel. 

Energy efficient LED TVs

LEDs are also more energy-efficient than traditional bulbs and require less power to illuminate the screen. The effect on power consumption can be dramatic, especially when compared to the LCD and plasma TVs we've already tested.

Use 40% less power with Samsung LED TV

Perhaps the most newsworthy is the Samsung UE40B7020 (right), a fine example of how new LED TV technology is pushing the boundaries of energy efficiency. 

It uses over 40% less power than a typical 40-inch LCD TV. Even more impressive is the 55-inch version (the UE55B7020), which uses only 109 watts switched on. That’s closer to the average for a 32-inch TV, and can be lowered even further (to just 89 watts) if the energy-saving mode is set to high.

LED television reviews

Follow the links to check full reviews of LED TVs.