LED TVs: 10 things you need to know

In Depth: Is LED better than plasma? Or should you wait for OLED?

HDTV News

By Dean Evans

September 21st 2009 | Tell us what you think [ 0 comments ]

Toshiba Regza SV with LED backlight - announced earlier this month at IFA

While we wait for OLED to mature as a mass market TV technology, inorganic LED TVs are giving LCD a significant performance boost.

Indeed, Samsung is so keen on LED that it has proclaimed it as the "next generation of television", capable of delivering brighter colours, deeper blacks and sharper images.

Should you believe the hype? Are LED-equipped LCD TVs better than plasmas? Isn't LED TV just a more efficient backlighting system? Here's the 10 essentials you need to know.

1. LED TVs don't exist
At least not in the way that Samsung is marketing* its 6-, 7 and 8-series LED TVs. These TVs are still LCD TVs at heart. But they use Light Emitting Diodes (LEDs) to backlight the screen instead of Cold Cathode Fluorescent Lamp (CCFL) technology. Inorganic LEDs are far too big to be used as individual pixels on a consumer HDTV.

But true LED-based screens do exist. The new $1.2-billion Dallas Cowboys Stadium in Arlington, Texas has two of them on the sidelines. Each one features 10.5 million LEDs arrayed cross 11,393 square feet of Jumbotron-style screen technology. Wow.

*The Advertising Standards Authority recently upheld complaints that Samsung's TV campaign for its LED TVs was misleading to potential customers. "We considered that the [Samsung] ad implied the TV displays were comprised totally of LEDs similar to some outdoor displays when that was not the case," said the ASA. "We considered that because the ads were ambiguous and did not make clear how the TVs utilised the LED technology, the ads were likely to mislead."

2. CCFL is an outdated technology
Traditional LCD TVs have always been criticised for their washed-out colours. This is because the big, dumb CCFL backlights they use are always on and light leaking through the LCD layer makes it nigh-on impossible to deliver a truly inky black. If you own an LCD and you watch a letterboxed movie on it, the 'black' bars at the top and bottom of the picture often appear distinctly 'grey'. That's the backlight shining through.

3. The first LED-backlit TV cost $15,000
Sony was first to market an LCD TV with an LED backlight in 2004. The 46-inch, 1080p-capable Qualia 005 incorporated a revolutionary Triluminos system that used a grid of RGB LEDs instead of a fluorescent lamp. Yours to own for the price of a new small car.

4. There are two types of LED backlighting
Today's LED-equipped HDTVs either employ a full-screen "local dimming' backlight" or an "Edge LED" solution. A HDTV with a local dimming system features an array of LEDs behind the entire LCD. Local dimming describes how clusters of these LEDs can be switched on and off, significantly reducing light leakage and enabling the TVs to deliver improved contrast, more vibrant colours and truer blacks.

In contrast, an Edge LED system effectively replaces CCFL backlights by positioning the LED elements in strips along the sides of the LCD. These focus light inwards into a light diffusion panel, which subsequently spreads the light evenly across the screen.

Sony bravia led

SIZE ZERO: Samsung's 46-inch UE46B8000 LED-backlit LCD TV is only 29.9mm thick, a size zero design achieved by using Edge LED technology

Which approach is better? A local dimming setup is certainly more effective, offering more control over the areas of the screen that are backlit. But Edge-lit tellies are all the rage these days.

As Samsung is keen to point out on its website: "Until recently, normal LED TVs placed LED lights at the back. Then Samsung's designers developed the world's first white Global LED TV, which positions the LEDs on the side next to the frame. The transformative technology has finally made exceptionally slim LED TVs a reality." Hammering the point home, Samsung showed off a 6mm-thick, side-lit LED LCD TV at this year's IFA.

5. LED TVs have some compelling advantages
LED TVs are also designed to light up quickly and can be switched off (or dimmed) just as fast. This enables an LED-backlit LCD TV to trump a CCFL-lit LCD TV with brighter images, greater contrast, superb clarity and deeper blacks. And when tri-colour RGB-LEDs are used in a local dimming array, the result is a much wider colour gamut and even better onscreen performance. The Sharp LC-52XS1E is a good example.

Sharp led