Most important TV specifications
The most important TV specifications which make a TV picture to be good and clear are the type of TV screen, TV Resolution and Contrast Ratio. Other specs like TV size, TV sound quality, etc. are important but for the clarity of the TV screen picture the top 3 specification of a TV to consider are the type of screen (OLED or LED), TV resolution (Standard resolution, High Definition, Ultra High Definition or 4K) and the Contrast Ratio. Each of these most important TV specifications are explained below.
Type of TV screen
There are basically four different kinds of wide flat screen TVs available. These are LCD TV, LED TV, Plasma TV and OLED TV (OLED= Organic Light Emitting Diode) TV. There are the old Cathode Ray Tube TVs, but they are almost discontinued now and so we will not discuss these old types of TVs. Plasma TVs were considered to have the best TV picture but for about 10 years now Plasma TVs are not being manufactured. Plasma TVs suffered a problem known as screen burn-in and also the picture was not very bright and for best viewing had to be seen in a dimly lit room. Anyway Plasma TVs are not available anymore and we will not bother about it. That leaves LED TVs and OLED TVs for now and we will concentrate on these types of flat screen TVs now available.
What pixels mean in a TV
Before we start explaining about the different kinds of TVs, we must first explain what a 'Pixel' is, because this is one of the most basic term which we should understand before discussing different types of TVs.
A TV picture has thousands of tiny squares known as Pixels as seen on the image here. A Pixel is the short form for ‘Picture Element’ and is the smallest element which forms a picture on the TV. If more pixels are used in a picture it becomes more dense and much clearer. As explained further down about TV Resolution, when more number of pixels are used to form a picture, we say that the TV has a higher Resolution.
What LED TV means
In LED TVs, the TV picture is formed on an LCD (liquid Crystal Display) panel. The LCD panel has millions of small liquid crystals which makes up each pixel (explained further below) of a TV picture. Each Liquid crystal in the LCD panel can switch 'on' or 'off' when a small electric voltage is applied. When 'ON' it becomes transparent and allows light to pass through and when 'OFF' it blocks light passing through. So the TV picture signal can apply the correct voltage to each individual Liquid Crystal in the LCD panel to produce a moving image. The LCD Panel needs a light source to project a picture on to the TV screen. This light source is provided by what is known 'Back-Light'. The back-light source in LED TVs are produced by LED light bulbs and that is why it is called an LED TV, so named due to the back light source. Earlier LED TVs used to be called LCD TV based on the fact that the screen which produces the actual TV picture is an LCD screen. But when more efficient LED light source replaced the older CCFL (Cold Cathode Fluorescent light) as backlight source, TV Companies started marketing it as LED TVs to boast about the more energy efficient and brighter white lights of the LED light source.
What OLED TV means
OLED stands for 'Organic Light Emitting Diode' and an OLED TV means a TV which has an OLED screen. The pixels on an OLED screen are made up of tiny OLED elements which produce its own light - self illuminating. So an OLED TV does not require a back-light and hence has very high Contrast Ratios. What Contrast Ratio means is explained further down. Because an OLED TV has such a high contrast Ratio, OLED TV is better than an LED TV.
OLED TVs are the same like AMOLED telephone screens and hence, very bright and can be viewed in well lit rooms, unlike the old Plasma TVs. Also OLED TVs do not have such a severe problem of Screen Burnin like the old Plasma TVs. At the moment OLED TVs are very expensive but the price will gradually come down as production increases.
What Contrast Ratio Means
Contrast Ratio means the difference in light density between a TV picture's brightest area to the darkest area in the picture. Contrast Ratio in a TV is calculated by dividing the light density in Lumens in the brightest, whitest part of a TV picture by the Lumen Value of the darkest, blackest area in a TV picture.
In an LED TV, the LCD screen picture has a bright back light to project the picture on the TV screen. This causes light to bleed into the darkest area of the LED TV picture and this decreases the Contrast Ratio of LED TV. On the other hand, in an OLED TV, the OLED elements produce their own light and in the dark areas the OLED pixel does not light up. Thus in an OLED TV the dark areas do not have light bleeding into it like in an LED TV. So OLED TVs have very high Contrast Ratio. The high Contrast Ratio in an OLED TV makes the OLED TV picture to stand out much clearer than in an LED TV.
What TV Resolution means
TV Resolution means how dense the TV picture is, or how closely packed the pixels are in the TV picture. TV Resolution is measured by the number of Pixels in the Horizontal direction multiplied by the number of pixels in the vertical direction. Thus for an High Density or HD resolution it is 1920x1080 pixels and for 4K UHD or Ultra High Density picture it is 3840x2160 pixels.
The following picture can best explain the meaning of TV screen resolution. The picture below compares the difference between a low resolution (left) and a higher resolution TV picture (right). Obviously the higher resolution picture has much more clarity and is a pleasure to watch.
The more the number of pixels in a TV screen of same size, the higher the TV screen resolution. The images above compare the pixels in an ordinary TV (left) and an HD TV (right). With the pixels packed closer together, there are much more pixels in the same area of a 4K TV than an HD TV and this means a much higher resolution picture. The closer the pixels are together the clearer the picture gets.For example an HD TV has 4 times more pixels than an ordinary TV and a 4K Ultra HD TV has 4 times the number of pixels there is in a full HD TV. Hence a 4K TV will look much sharper, especially close-up.
The image here represents the mosquito net like pixel arrangement on the screen of a TV. The same letter ‘A’ looks distorted on the left due to wider pixels owing to fewer pixels than on the same letter ‘A” on the right which has more pixels and the pixel net pattern is packed closer together. Thus the more pixels there are on the TV screen the better the picture will look.
The area the letter ‘A’ occupies in both the pictures is the same, thus when there are more pixels in the same area, the letter ‘A’ is much clearer. Same thing applies to a TV screen. A TV of the same size screen having more pixels will be much clearer and is called a TV with a higher resolution. Resolution is therefore the number of pixels in a fixed area. Theoretically therefore Resolution can be called the Pixel Density on a TV screen.
In practice all HD TV screens have 1920 pixels horizontally in the ‘x’ direction and 1080 pixels vertically in the ‘y’ direction. This is usually written as 1920×1080 pixels. For a 4 K Ultra HD TV screen the pixels are packed 3840 horizontally and 2160 pixels vertically or 3840×2160 pixels. The ‘K’ in the 4K stands for ‘Kilo” which is a thousand. Thus 4K means 4,000 and in the 4K UHD it signifies the 3840 horizontal pixels which is nearly 4000.
TV screen size meaning explained
TV screen size is the most important TV spec that matters most to most people. How is TV screen size measured is explained as follows. The size of a TV is the measurement of the TV screen size diagonally from top corner to bottom corner on the other side- for example from top right corner to bottom left corner, in inches in USA and UK and in centimeters or cms in most other countries. Only the visible screen area is measured when measuring the size of a TV, the side frames are excluded.
The picture above shows how a TV is measured, the green coloured measurement is wrong and the red colored measurement is correct. The dimension in the red colour showing the TV screen size of only the screen and excluding the frame is the correct screen size, in this case the TV screen size is 46 inch and not 51 inches shown in green. Since one inch is equal to 2.54cms (centimeters), the Metric TV size of this 46 inch TV will be 116.84 centimeters. The decimal points are usually rounded off and thus the 46 inch TV in India will be a 117 cms TV.
How far to sit from the TV
When watching TV a common question is “how far to sit from the TV”? It depends on the TV size on how far to sit from the TV when seeing TV. The resolution of the TV also plays an important role on how close you can sit from a TV to watch TV. High Definition TV and 4K ultra HD TV allows you to sit much closer than to a Standard definition TV. This is because the pixels in 4K Ultra HD TV and HDTV are packed so close together that you cannot see the pixel net like structure in the TV picture even sitting close up to the TV.
As a general rule the HDTV viewing distance is a minimum of 1.5 times the screen’s diagonal measurement, but for regular viewing it is better to sit a bit further. Thus the optimal best viewing distance for 60 inch HD TV will be at least 90 inches or 7.5 to 8 feet (about 2.3 meters) from the TV screen.
There are no official bodies, as yet, to recommend viewing distance for TV size. Various TV magazines and TV testing bodies recommend various Television Screen Sizes to Viewing distance. From a selection of these recommendations, we have made a TV Size Viewing Distance table below. It only gives you a rough idea of the recommended viewing distances. The maximum distances are flexible, but the minimum distance mentioned in the table below, is the minimum obtained from several sources, so that should be followed.
|HDTV screen Size||Minimum Distance||Maximum Distance|
|32″||4 feet||13.5 feet|
|37″||4.6 feet||15.3 feet|
|40″||5 feet||16.3 feet|
|42″||5.25 feet||17 feet|
|46″||6.75 feet||18.3 feet|
|52″||6.5 feet||21.3 feet|
Further knowledge about TV sets
We have summarised only some of the important points regarding TV sets here. We have a dedicated website explaining all about TV sets and we invite you to please go through that website for more knowledge about TVs. This is the link to our website www.WhatTVs.com
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