Ashish Narsale explains how some companies are promoting LED backlight TVs as LED TVs.

Want to buy LED (light-emitting diode) TV? Is this the right time? Know the basics before you buy. There are many options available to you in the market today, and many luring offers.

So, your pocket willing, the only question you must be facing now is which LED TV to buy?

But, are LED TVs actually LED TVs? Well no, they are the same conventional LCD (liquid crystal display) TVs but with LED backlight (or backlit, both are used interchangeably) instead of CCFL (cold cathode fluorescent lamps) backlights used in standard LCD TV.

It's a different thing that some companies are promoting LED backlight TVs as LED TVs.

Before you convert your impulse into a reality let's first understand what is CCFL backlight or conventional LCDs.

CCFL backlights are actually an array of CCFL tubes arranged behind the LCD panel that light up the pixels on the LCD screen. As these CCFL tubes are never turned off when the TV is on you don't get perfect pitch black colour in a standard LCD TV and hence they have low contrast ratio (higher contrast ratio renders rich and vivid colours on the LCD screen).

The other drawback is CCFLs take up more energy and produce more heat and so are not very eco-friendly.

On the contrary, LEDs are more energy efficient, brighter, and produce extremely less heat than CCFLs. But the story doesn't end here. There are variety of LED backlight panels available and each have their pros and cons.

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At present there are four variants available:

Full-array or full LED without local dimming

These TVs are same as standard LCD TVs. Just that the CCFL backlights are replaced with LEDs. The full-array means the LEDs are arranged behind the entire LCD panel. Picture quality is same as LCD TV.

To make it simple for you, you can call them full LED backlight LCD TVs.

Full-array or Full LED with local dimming

It's an original concept and is still best among the lot. These are best performing LCD TVs in the market at present.

They are same as Full LED TVs but have dynamic backlight LEDs where each LED is controlled dynamically, that is, dimmed or brightened individually.

As the dimming of LEDs is controlled when viewing dark or black moving pictures the LEDs covering the dark shades are dimmed or turned off and bright areas LEDs are brightened to give you crisper image quality, better black levels and uniformity than normal LCDs and leads to less leakage of white light.

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Edge-lit or Edge LED without local dimming

Call this the talk of the century. The thinnest TV set world ever designed! What makes them thinner? The Edge LED technology, wow!

That's cool, but wait, hold you excitement. There are things to know before you dip into your wallet and bring out that cheque book.

Let's talk about the technology; again it's the same LCD TV but this time the LED backlight are not arranged behind the LCD panel but on the edges and centre, and other areas of the screen are illuminated by so-called light guides (for instance, a strand of fibre optic can act as a light guide).

These features make it possible for designers to design thinnest LCD TVs. Now here your excitement goes down the ditch as the LEDs are placed on the edge of the panel and so they fail to show uniformity, that is, brighter edges compared with the centre of the LCD panel.

Edge-lit or Edge LED with local dimming

These are same as the Edge LED backlight LCD panel, rather advanced having dynamic LED dimming.

The LEDs on the edges are controlled dynamically with respect to moving picture, that is, dimmed and brightened but the end result is not as good as the Full LED panel output on which each LEDs are placed behind each pixel to give you accurate output.

Because of the placement of LEDs the dimming takes place only along the edges and other areas illuminated by light guides.

So the best of the lot would be the Full-array or Full LED TVs with local dimming but they are rather very expensive.

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