If you believe the hype, LED-illuminated LCD TVs deliver brighter colours, darker blacks, thinner designs and help save the planet, while also making you a cup of tea, with a splash of soy milk and one organic sugar. Hot beverages aside, there's plenty of truth in those claims, with recent advances in display technology leading to increasingly power-efficient tellies that look better than ever.
LED TVs have quickly become mainstream, partly because their slimline designs look so much more attractive than older LCD models. Eyes right for a selection of the best-selling and top-rated LED-illuminated TVs that we've seen.
The technology isn't actually all that different to what's used in LCD sets. All LCD TVs need a backlight. A backlight is a light source that shines on coloured pixels, which either let the light through or don't, building up the image you see. Plasma TVs don't need a backlight because each of the hundreds of thousands of tiny cells in the screen generates its own illumination.
Older LCD televisions use a couple of fluorescent lamps as the backlight, with a plastic sheet in front of them spreading the light evenly across the LCD panel. Whenever the TV is turned on, the lamp is turned on, using electricity all the time.
Edge lighting versus backlighting
There are two types of LED televisions, both of which replace the fluorescent backlight with hundreds or thousands of tiny LEDs. The simpler and cheaper technology is LED edge lighting, which runs a row of LEDs along the edges of the screen, with a special diffuser panel that directs their light into the display. LED edge lighting allows LCD televisions to be much thinner than before, going down to just a few millimetres. LED edge lights also consume less power than fluorescent backlights and are better for the environment, containing fewer toxic materials.
The other technology is direct LED backlighting, which is the more expensive option. An array of LEDs behind the LCD panel switches on only when necessary, so, if you're watching a film of a black cat in a coal mine, the television will hardly use any power at all. This is called 'local dimming' because the illumination of each part of the screen is adjusted individually.
Direct LED backlighting delivers a fantastic contrast ratio, from pitch-black to supernova-white, as well as rich, extremely natural colours. It uses even less power than LED edge lights and around a third less than normal LCD screens.
Each TV maker uses a different number and type of LEDs, so always view a few tellies to see which you prefer. Whichever you choose, LEDs are incredibly reliable and all LED TVs should last at least as long as traditional LCD televisions, and probably much longer. Some manufacturers quote lifetimes of up to 100,000 hours or more. That's 35 years of viewing at 8 hours a day.
Other aspects to consider include the refresh rate and viewing angle, in which regards LED-illuminated televisions might not be better than normal LCD ones. Wider viewing angles are better for large families (with plenty of people arranged around the screen), while 100Hz motion control, or higher, will help smooth high-speed action. Also look out for the ability to tweak the colour settings to suit your own viewing conditions and tastes.
Finally, don't forget the audio side of the equation. The skinniest LED tellies don't leave much room for decent speakers, so close your eyes and see if you still love that ultra-minimalist set quite as much. If not, budget for a home-cinema system so you can enjoy full surround sound.
One last word. Although OLED screens sound similar to LED TVs, they're actually a completely different screen system. Both Samsung and LG will be launching ultra-thin flagship OLED screens this year, with virtually bezel-free designs. But you can expect to pay through the nose for the privilege. Mark this down as a technology to watch, rather than a practical choice straight away.