How Does LED TV Differ From LCD TV?

LED HDTVs achieve a much higher contrast ratio
October 19, 2009


Just when we had all sorted out the difference between Plasma and LCD flat-panel HDTVs, now we have LED HDTVs to consider too! However, there still seems to be a fair bit of confusion surrounding what exactly an LED TV is. Well, basically, it’s another form of LCD TV that uses LEDs to provide its light source.

Today Gizmag published an article that does a nice job of educating us about LED TVs. Their article summarizes what's different with LED TV vs. LCD TV in this paragraph: "All LCD TVs are backlit because LCDs are a transmissive type of display technology, which means they don’t produce their own light. So for an LCD television to produce an image on the flat panel display, its pixels have to be backlit by a separate lighting source. Currently, most LCD TVs used CCFL technology (cold cathode fluorescent lamps) as their backlight source. They deliver good colors and brightness, and decent contrast, but not great blacks – the domain of the plasma TV. But TVs utilizing brighter LED backlighting can achieve much better blacks, as well as brighter colors and even greater contrast ratios (Toshiba Regza 55X1 is boasting 5,000,000:1). NB: Contrast is measured from the darkest lit area of the screen to the brightest area to give a ratio".

Since LEDs provide a brighter light source, the flat-panel displays using them are significantly thinner than plasma or LCD displays. However there are two major LED technologies for the TV manufacturers to consider , edge lighting and full-array backlighting.

Edge lighting is pretty much as described. In this method, a series of LED backlights are positioned along the outside edges of the screen. From there, the light is dispersed across the screen, which means the LED/LCD TV can be made very thin. However the edges of the screen appear to be brighter than the rest of the display.

Manufacturers with currently released LED TVs are favoring full-array LED backlighting, where many rows of LEDs are placed behind the entire surface of the screen. Although this makes for a thicker TV panel, the LEDs provide more even, brighter colors and greater contrast. A measurable benefit of full-array lighting can be seen when "local dimming" is utilized, meaning that each LED (or more common, a selected “zone” of LEDs) can be turned on and off independently within the screen, thus providing greater control of the brightness and darkness for each of those areas. Greater contrast levels are achieved by diminishing the effects of light from brightly lit neighboring areas seeping into blackened areas of the screen, which is one of the downsides of LCD screens.

The following table provides a contrast ratio and price comparison for 3 brands of 46" LCD and LED HDTVs available now:





Manufacturer Model Contrast Ratio MSRP
Samsung LN46B650
LCD 1080P 120hz
100,000:1 $1,999.99
Samsung UN46B6000
LED 1080P 120hz
Ultra Slim
3,000,000:1 $2,599.99
Sharpvision LC46E77U
LCD 1080P 120hz
XD Engine $1,599.99
Sharpvision LC46LE700UN
LED 1080P 120hz
2,000,000:1 $2,199.99
Toshiba 46XV645U
LCD 1080p 120hz
REGZA
50,000:1 $1,399.99
Toshiba 46SV670U
LED 1080p
Thin
2,000,000:1 $2,299.99


To view the complete Gizmag story click here.

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