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Nov 30, 2009, 04.35 PM IST | Source: Chip Magazine

A guide to LCD & LED TVs!

LED TVs are the current focus of all the push, with Samsung and Sony leading the bandwagon.

A guide to LCD & LED TVs!
The HDTV market, today, makes all kinds of claims and advertisements, confudsing the buyers. The so-called LED TVs are the current focus of all the push, with Samsung and Sony leading the bandwagon. For anyone planning to buy one this month, I feel I have to write this short guide.

I have respect for all the major electronics brands; we review their products regularly, including the ďLED TVsĒ, but their marketing terminology is wrong. These are not LED TVs, ie, they donít substitute the regular LCD for an array of LEDs (which would give us incredible quality and power savings), but simply regular LCD TVs made of liquid crystals just like normal LCDs. The only difference is that LEDs are used to light the panel. Letís backtrack a bit in to the tech behind an LCD TV.

An LCD needs a source of light to work, unlike plasmas and OLED screens in which the pixels themselves emit light. This light is usually generated by a cold cathode lamp (CCFL), similar to the CFL lamps that light up our rooms. This is called the backlight, and is responsible for a huge chunk of the quality you will get out of the TV. These generally have a brightness of 330 Ė 350 cd/m2 brightness at their midpoints. Their evenness and brightness of the backlight dictate your panelís ability to show good pictures. The CCFL lights the LCD panel, which is made up of pixels, from behind. Each pixel either blocks the light to show black, or totally allows it through to show white. Each pixel is made of 3 subpixels: red, green and blue. These intermix as and how needed, and thus we get color. Essentially itís the TVís ability to block or let through the backlight that dictates the image quality in terms of brightness, contrast, etc.

Now in LED TVs, especially the Samsung ones released in India, the CCFL light is replaced by an LED source. These are definitely a better choice than the fluorescent cathodes since they consume less power, which makes power efficiency go up. Now we have another issue here. LEDs can light the panels from the back or from the sides. The ones we have reviewed so far light it from the sides, and are correctly referred to as LED edge-lit LCD TVs. Thatís what we call our reviews of such products.

It is debatable whether Samsung and Sony's ads are correct; maybe they should be more specific in their nomenclature, but then history is filled with marketing gimmicks and half-truths so thereís no use complaining about it. LED backlit LCD monitors are available in laptops and 21-23-inch and larger monitors. Samsung themselves have released an LED backlit monitor, called the XL2370, which should launch here soon. The Samsung 7 series edge-lit TVs are superbóthereís no doubt about thatóbut right now they are pretty pricey. I feel buyers should wait a bit unless theyíre really blown away by the image quality.

So then finally, what exactly is an LED TV? If these existed, they would actually use LEDs to make up the pixels, and would use totally different technology. No consumer TV currently uses LEDs; only some giant outdoor screens used in stadiums or hoardings line the ones you see in pictures of Times Square. These utilize up to 25 million LEDs each to produce full-color HD images, and no, I donít think anyone has one in their house! Sony has something called an OLED TV, the XEL-1, but the price is a joke and the technology is still different from normal LED LCD TVs. LGís LH90 is an LED-backlit LCD TV, and we also have BenQ's V2200 and V2400 monitors which use LED backlighting too. Traditional LCDs are not dying out by any stretch of the imagination; in reality they are just taking a backseat in terms of marketing jargon. Donít get taken in by a flashy ad or sales pitch!

By Siddharth Bhatia

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