LCD & LED TV screens

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Many people get confused between
LED screens and LCD screens – it’s easy to see why as only a letter separates them! However, the technology and the application is fundamentally different.

LCD Screens vs LED Screens
The basic difference between LED screens and LCD screens is in the way they are made. With an LED screen, each pixel is comprised of several small LEDs, rather than projected from a cathode ray tube or utilising liquid crystals the way an LCD TV does.

Each cluster in LED screens is comprised of a red, blue and green LED and they light up as required to make individual pixels that form to create the picture over the whole screen. This method differs from how LCD screens work in that the picture in an LCD model is produced by electrically ‘relaxing’ twisted liquid crystal molecules and passing light through them from a backlight. A completely relaxed molecule will become almost completely opaque, while a fully twisted one will allow the full luminosity of the backlight through, and this method creates the picture which is shown on the screen.

To further complicate matters, recently manufacturers have introduced LED screens to the home market. Confusingly, these aren’t actually LED screens, but LCD screens that simply use LED backlighting rather than a traditional tube, helping to enhance contrast and colour levels.

The two technologies are used for hugely different applications – although these so called LED televisions are being released for home use, LCD screens are for use in indoor environments, typically for close viewing and for use as either televisions or computer monitors, while LED screens are more suited to large screens such as those seen at music festivals.

Why LED Screens Are Better For Large Screens
LED screens are usually used as displays at music festivals, large concerts and sporting venues and they are far better suited to this application than LCD or plasma screens.

The key reasons for this are:

Brightness – We’ve all seen what an LCD screen or CRT television looks like when the sun shines on it – you can’t see the picture. LED screens use incredibly bright LEDs, designed specifically to be visible in bright sunlight. This is the key strength of LED screens; LCD screens simply are not usable in an outdoor environment. The same goes for projectors – these are only effective in low light conditions; fine if it’s a dark night, but not much good during the day!

Strength – LED screens are made up of individual panels which are put together seamlessly. Imagine if you were to do that with LCD screens? Besides having borders around each panel, they are very fragile and easily cracked if moved around a lot, and once this happens the LCD screen is useless. LED screens are far more robust and easy to service – should an LED be broken it is easily replaced – making them far more usable as well as cost effective.

Impact – If you want your message to stand out, then LED screens are the way to go, as they are bigger and brighter with much richer colours.

What is pixel pitch?
Pixel pitch is the distance between each cluster (pixel) of LEDs and is a common term in LED screen technology. In the most basic terms, the smaller the pixel pitch, the closer the pixels are together, meaning the closer the viewing distance before the picture becomes pixelated (as it would do if you put your face very close to your tv).

Most manufacturers use something called ‘virtual pixel technology’ (or a variant of), which very cleverly shares LEDs between pixels, thus effectively doubling the resolution of the screen, so it is not uncommon to see an LED screen specification that says real 20mm, virtual 10mm.

For usual outdoor application, it’s important not to get too hung up on the pixel pitch of an LED screen as most such screens are around the 20mm (1omm virtual) mark and are perfectly suited for audiences over 4-5m away.

Pixel pitch becomes more important for indoor screens, particularly when likely to be viewed from very close up. It’s not uncommon for screens with a pixel pitch of just 4mm to be used for such applications!

Is an LED screen the same as a Jumbotron?
Jumbotron is a brand of LED screens – it was one of the first to market, so – like Hoover – has become synonymous with the technology in some areas of the world. Other brands you might hear people make reference to are Barco, Starvision, Diamond Vision, Daktronics, digiled and of course ADI’s Virtuality. All of these are LED screens based around similar technologies.

Courtesy: www.adi.tv/