Everything you need to know about LED TV


By: Shravan Kumar (LT RLBU)

We often hear about LCD, LED, HD, full HD, IPS etc. when we walk into a television sales store. I used to wonder why televisions of the same size and with similar experience while watching, varied so drastically in costs. Upon asking the sales man he took me on a rollercoaster ride of ‘unknown – extra terrestrial – never heard’ technical terms which threw me back and made my doubt my credentials of a hard earned engineering degree. Well, this article will break down the basics of working of the latest LED TVs’ and probably help you in deciding which one will suit you the best.

LED TVs’ are trending in the market and these televisions are the successors of LCD TV. LCD- liquid crystal display means that a Liquid crystal is used to make images. There is a liquid crystal in the back ground whose density varies according to the voltages of the positive and negative electrodes surrounding it. This crystal is lit by the LED on the back and the colour of light is varies with the density of the liquid crystal.

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Whereas in the case of LED TV, Each LED illuminates a pixel on the screen. There are a millions of LED in each LED TV which have the ability to change colour and hence we find an image every time a LED is lit.

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Now the question is, how many LED do we need in a TV? This factor exactly defines the detailing in a picture. We need to understand that one LED can show only one colour at any given instant of time. If we consider each LED as a dot (pixel), the collaboration of many dots in a pattern forms, a picture. This should explain how we are able to see a colourful picture on a TV. As the number of sots (pixels) increases, the detailing in the picture increases. We are looking at two parameters here:

  1. The size of the screen
  2. Number of pixels in the screen

For a better clarity we will need more number of pixels in a smaller area, which is called pixel density and is equal to number of pixels divided by the screen size.

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This will help you decide why an image on 1080p, looks sharper than on a 720p. Depending on how far you are going to watch the picture from, you can decide which one among 720p ‘HD’ or 1080p ‘HD ready’, 2160p ‘4k Ultra HD’ will suit you. We are now able to see a still picture, but what happens inside an LED TV for a motion picture.

If you know about the earlier technology of playing a movie, there used to be a reel of film, which was rotated either manually or by a motor and each element (frame) of the film, was lit up to form an image on the screen. When watching pictures on a screen we see that he objects are moving but if we inspect each element of the film individually, we will be able to identify each element (frame) separately as a stable picture.

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A human eye cannot exclusively identify each frame if the frames are moving at a speed greater than 1/16 of a second. So if the frames are moving at a speed greater than a speed beyond which the human eye fails to distinguish between consecutive frames, the frames start overlapping and we feel that the object in the picture as moving. Hence the clarity of a motion picture is dependent on the number of frames that are moving per second.

What happens in a LED TV is that the LEDs blink for each frame. Each of the frames aligns the complete set of LED to show a certain pattern. As a new frame approaches, the LED’s colour gets realigned to show a new frame. This realignment happens at a rate of 60 – 240 frames per second. Hence, a TV with higher frequency of Frames is least likely to show a blurred image than a TV with less frequency of frames.

Now we are clear that, a TV with higher screen size with greater pixel density and higher frames per second is bound to be costly and will be providing a great experience while watching a picture in it.