TV Basics, How to buy a TV, What Size TV to Buy?

How to buy a TV? You can depend on Flat Screen TV reviews, but don't you think that you should understand as much as possible about what is a Flat Screen TV and how they are specified. Here we will discus about Flat Screen Televisions and what to look for when buying a TV. TV Specifications Explained in short, just enough to understand the concept, are presented in the following page. These Basic TV specifications are common for all types of Flat Screen TV. After you have decided on the size of the TV, you have to decide on either 3D, LCD, LED or Plasma TV. For this please visit our page LCD, LED, Plasma Compared and 3D TV

TV Specifications Explained

We list below the important TV Specifications and when you click on any, it will take you to a detailed explanation of that particular specification.

• TV Size Explained
• HD Ready vs Full HD TV
• 4:3 Picture size on a 16:9 TV
• TV Viewing Distance Chart
• TV Resolution Explained
• 'Ultra High Definition TV' or 'UHDTV' or 'Ultra HDTV'
• TV Aspect Ratio
• TV Contrast Ratio
• TV Viewing Angle
• TV Refresh Rate explained, Motion Interpolation, TV Hz explained -Terms like 100Hz, 120Hz, MotionFlow, Clear Motion, TruMotion, IFC, etc
• TV Interlaced vs Progressive Scan the 'i' and 'p' after the 720 or 1080 resolution.
• 24P : Terms like '24p True Cinema', '24p Real Cinema', etc
• TV Audio Output Power

High Definition TV explained - Sample of HDTV

Before we go into the details of TV specifications, let us first compare how HDTV compares with ordinary TV. The picture below shows you a side by side comparison between the higher resolution High Definition TV and a standard non High Definition TV. As they say, a picture is worth a thousand words: HD Television explained better with a side by side picture comparison below. The improvement in the quality of the HDTV picture is obvious.

HDTV vs Standard TV. Left half HDTV, right is Standard TV

TV Screen Size

Let us start with the most basic specification, the Flat Screen TV dimensions. The size of a television is measured by the diagonal measurement of the visible screen area, excluding the side frames. The picture on the left demonstrates the measurement of a 42 inch TV. Since one inch is equal to 2.54cms (centimeters), the size in the Metric system, will be written as 107cms. The actual measurement may differ a little, but the decimal points are rounded off. TV normally comes in the following standard sizes ( " = inches) 22", 26", 32", 37", 40", 42", 46", 55"and , 60".

TV screen size calculator: You can calculate the width and height of the TV screen by using the Pythagoras Theorem as shown in the picture on the right. This can help in knowing before hand the approximate size required on your TV stand or wall. Thus a 40 inch TV dimensions are approximatly 35 inches wide and 20 inches tall. Similarly a 42 inch TV dimensions are approximatly 37.5 inches wide and 21 inches tall.

It can also help you to calculate size of 4:3 picture on 16:9 TV. Let us assume you have 32 inch 16:9 LCD TV and you want to calculate the size of a 4:3 picture viewed in the normal view of the 32" 16:9 television. Using the Pythagoras Theorem the diagonal d=32 inch, therefore the height 'a' in the figure is calculated as 15.75 inches. Since ratio is 4:3 the width will be 21 inches. So the 4:3 diagonal size is 26.2 inches on the 32" 16:9 TV. That means the 4:3 picture you see on a 32 inch 16:9 ratio TV is equivalent to a 26.2 CRT TV with a 4:3 ratio. For a 40 inch 16:9 ratio HDTV, the 4:3 picture you see on it will be the equivalent of watching it on a 33 inch 4:3 TV.

TV Viewing Distance Chart, TV Screen Size Viewing Distance

Before buying the TV it is good to know the recommended viewing distance, that is the distance from the TV screen to the approximate position of your eyes when viewing the TV regularly. The 'TV Size Viewing Distance' should be an important factor to decide on the size of TV you buy. If you sit too close to a standard television, picture quality will be poor, but High Definition TV (HDTV) allows you to sit much closer and view a very clear picture. 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.

There are no official bodies, as yet, to recommend TV screen size viewing distance. Various TV magazines and TV testing bodies recommend various Television Screen Size Viewing distance. From a selection of these recommendations, we have made a TV Viewing Distance Calculator or a TV Viewing Distance Chart below. It only gives you a rough idea of the recommended viewing distances, it is not a strict rule. The maximum distances are flexible, but the minimum distance mentioned in the table, is the minimum obtained from several sources, so that should be followed.

The diagonal screen size are in inches are for HDTV. This TV Size Viewing Distance Chart should help you in choosing the right size of Television for your room. There should be about 3 inches of space on each side of your television for proper ventilation. A few inches should be added for the thickness of the television - say 3 inches for an LCD TV. This means that the LCD TV screen will be about a 6 inches from the wall, when it is wall mounted. If kept on a TV stand or table, then this distance will be increased. Also note that TV viewing height, especially for HDTV are best seen at eye level, this should be kept in mind when you decide on the place to keep the TV.

TV Viewing Angle

TV Viewing Angle explained as how far to the left or right you can sit in front of the TV. If you are sitting straight in front, you are sitting at Zero degrees, as you go right or left the angle increases to 90 degrees when you reach a point parallel to the TV. Most TV manufacturers specify the total viewing angle, that is from the left extreme to the right extreme. The maximum possible in such a case will be 180 degrees, that is 90 +90. The best viewing angle TV will be straight in front of the TV.

TV Aspect Ratio

This is the ratio between the width and height of the screen. HD TV has an aspect ratio of 16:9, CRT TV has an Aspect Ratio of 4:3 . As a TV Aspect Ratio guide we will make a TV Aspect Ratio comparison of common TV formats like 640:480 which is the same as 4:3, similarly 1280:720 and 1920:1080 works out to 16:9. These are not the only TV aspect ratios, there are several other TV Aspect Ratios which are available from TV Aspect Ratio Chart available from the net.

Many countries still transmit TV signals in the 4:3 format which is still the Standard TV Aspect Ratio in many countries. Hence when you view a normal 4:3 format movie in 16:9 format, the picture stretches sideways, making people and objects look fatter. You press the 'Aspect Ratio' button on the remote control to correct this problem.

When a 16:9 movie is squeezed and compressed into 4:3 format movie, people and objects look very thin. When widescreen video images are squeezed to fit a narrower aspect ratio it is called 'Anamorphic Video'. When expanded into 16:9 ratio they look normal. Here again you press the 'Aspect Ratio' button on the remote to view the movie in the 16:9 format. Click here to see how you can calculate the size of the equivalent 4:3 picture on a 16:9 TV

TV Pixels & TV Resolution Explained

Pixels is the short form of 'Picture Element' and is the smallest element which makes the picture. If you go close up to any television you should be able to see pixels similar to the picture on the left. The more number of pixels a TV picture is made up of, the sharper the picture gets. In HDTV these pixels are barely visible and you must go really close up to see them.

Resolution theoretically should be defined as the number of pixels per unit of measurement, for example so many pixels per inch, but this is not the case for TV. TV resolution is fixed and is expressed by the total number of pixels horizontally into the number of pixels vertically.

HD Ready vs Full HD TV

Full HDTV has 1920 horizontal and 1080vertical pixels(1920x1080). This is called the Native Resolution of the TV and is commonly written as 1920x1080. The 1080 is the number of pixels top to bottom, and it is also known as the number of scanning lines to form the picture on the TV. HD Ready TV has resolution of only 1280x720 or 1,366x768. In Digital Camera talk, the full screen in an HDTV will have 2.07 Million or Mega Pixels. For HDTV ready TV it will only have 0.92 Mega Pixels. Thus you can imagine the difference in image quality of HD Ready vs Full HD TV. We have a sample picture for your comparison at the top of this page.

The term 'HD ready' was introduced by 'The European Industry Association for Information Systems' (EICTA). 'HD ready' means the TV has the minimum screen resolution (at least 1280x720) and digital sockets (HDMI or DVI) to receive and display an HD picture. HD ready is not a High Definition TV, but it can play HDTV to give a picture quality that is near the quality of HDTV. When you want to buy a full HD-TV, make sure that the 'Native Resolution' of the TV is 1920x1080. Also for an HD ready TV the minimum viewing distance is more than that for an HDTV.

The picture below shows the grid diagram or graphical representation of pixels in TV of different resolutions.

Pixel Resolutions of different TV displays.

Ultra High Definition TV or 'UHDTV' or 'Ultra HDTV'

'Ultra High Definition Television' or 'UHDTV' or 'Ultra HDTV' also known as 'Super Hi-Vision' or 'Ultra HD' is a future new digital video format proposed by the Japanese public broadcasting network, NHK. Ultra HDTV is four times the width and height of the present HDTV and therefore has 16 times the resolution of the present HDTV. Ultra HDTV or UHDTV has 7,680×4,320 pixel resolution Vs. the 1920x1080 resolution of the present HDTV. In pixel terms that is 33 million pixels (7680x4320), compared to a maximum 2 million pixels (1920x1080) in our best HDTV of today. Ultra High Definition TV 2160p is already in service now in Japan.

The UHDTV is becoming closer to reality with the International Telecommunication Union (ITU) proposing to have the technical specifications approved by them by April 2012. BBC with NHK, hopes to do some test UHDTV recordings at the 2012 London Olympics.

TV Electron Scannig

How is the picture formed on the TV screen? In a very simplified way, we can explain how a picture is formed on a TV by the use of the picture on the right. In a CRT television the picture on the TV screen gets "painted" on the screen. An electron beam "paints" the image on the screen by moving from left to right starting from the top left hand corner (1). When it reaches the other end of the screen the beam offs and quickly moves back to the left side (2) and at the same time going down a little bit. It repeats this process till it finally reaches the bottom right hand corner. Now the beam has painted one frame of the TV picture on the TV screen. The electron beam offs and then moves back up and repeats the process (3). All of this is done in fractions of a second, since the beam has to paint about 25 full pictures on the screen per second. As the beam paints each line from left to right, the intensity and characteristics of the beam is changed to create different shades of colours across the screen.

There are 3 standard resolutions for the number of horizontal lines. In the old CRT TV it was 480 lines. The HD Ready and the ordinary DVD players have 720 lines. HDTV and Blu-Ray DVD players have 1080 lines.

TV Interlaced vs Progressive Scan

TV transmission companies, in order to reduce the Bandwidth required to transmit TV pictures, devised a method by which each frame of a picture is split into 2. The odd lines starting from the top, that is line 1, line 3, line 5, etc are made into one frame. Similarly the even lines 2, 4, 6, 8, etc are made into the second frame. This means that the TV transmitting station only has to transmit only half the picture information or data at a time, even though, instead of 25 frames per second they now have to transmit 50 frames per second. This method of transmitting is called 'Interlaced Scanning'. The TV now receives 50 frames per second and it combines 2 frames into one and shows it on the TV. The 'i' after the horizontal line numbers represents that it is an interlaced signal.

TV 1080p explained

Progressive Scan on the other hand transmits the complete picture at the same time. The 'p' after the horizontal line resolution stands for progressive. Of the two scanning methods, the Progressive Scan is the better one, because it avoids problems like 'judder' or 'jitter' or 'flickering' in the TV full picture when the 2 interlaced pictures are combined. So in effect the best quality picture from today's TV technology is available from a 1080p device. Right now, in India 1080p is only available from Blu-ray DVD.

TV Refresh Rate Explained - Motion Interpolation and TV Hz explained

You will come across the terms like 100 Hz, 120 Hz, 240 Hz, 480 Hz, 'Auto Motion', 'AquoMotion', 'ClearScan', 'Fine Motion', 'MotionFlow', 'Natural Motion', 'TruMotion', etc. while researching for your TV. All these terms refer to the Refresh Rate of a TV. TV Hz explained like this : additional frames are interpolated or added between the frames in the original broadcast signal. Obviously the best refresh rate for TV will be the higher number. For example 600hz TV explained as 600 frames per second. This is about the maximum that human eyes can make out, there is a limit above which humans cannot distinguish the difference in Refresh Rates. For a full explanation of frames and the scanning electron beam Please see above by clicking here. The Hz is the symbol for 'Hertz' and is a measurement of frequency, the number of cycles per second. For example in India our electricity is Alternating Current or AC supplied at 50Hz. In the US it is supplied at 60Hz. With reference to TV, the Hz stand for the number of times per second, the electron beam paints the TV screen from top to bottom.

The frame rate is different from the scan rate. The frame rate is the number of time a different new picture appears on the screen per second. The refresh rate is the number of times per second, the scanning electron beam paints from top to bottom. These numbers can be different, since while refreshing, the same picture can be shown again and again. For example if the frame rate is 30 per second and the refresh rate is 90 per second, then each picture of a frame will be shown repeatedly 3 times while refreshing.

Higher refresh rates were introduced to reduce eye strain due to flickering of the picture in the old CRT TV. On the newer TV they are used to make fast action scenes to appear smoother and not to cause 'Judder' or 'flickering in Movies shot at different frame rate.

24p Movie Frame Rate Vs. TV frame Rate

Movie Films are recorded at a frame rate of 24 frames per second. Television on the other hand is recorded at 25 or 50 frames per second in PAL, the TV transmission standard in India. In the US it is recorded at 30 or 60 frames per second as per the US system called NTSC. this difference in the frame rates causes a problem to show movies on TV and causes problems like judder or flickering. To overcome this additional frames are simply duplicated as necessary until the timing of the movie and TV frame rates are equal. To achieve perfect match, it is preferable that the frame rate of the TV are in perfect multiples of 24 - that is 24, 48, 72, 96, 120 and so on. TVs with such perfect multiple refresh rates can show movies better than others. Terms like '24p True Cinema', '24p Real Cinema', etc refer to TV having this feature of playing movies in either 24 frames per second or in perfect multiples of it.

TV Contrast Explained, What is Dynamic Contrast Ratio?

The bigger the Contrast Ratio of the TV the better it is. As an example a TV with a contrast ratio of 6,000:1 is a better TV than one with a contrast Ratio of 3000:1

Contrast ratio is the ratio of the screen's maximum brightness or the whitest area to the darkest blacks on the screen. There two types of Contrast Ratios - Static Contrast Ratio and Dynamic Contrast Ratio. Static Contrast Ratio is the ratio between the blackest black and the whitest white that the TV can display. Dynamic contrast ratio is a feature built in the TV, which automatically adjusts the contrast and brightness based on the darkness of the image.  To improve the Contrast Ratio of LCD and LED TVs, the backlight of these TV is dynamically adjusted to match the brightness or darkness of the picture playing on the LCD or LED TV.

For the best Contrast ratio a black object on the TV screen should have no light at all, that is it should have a value of 'zero'. Therefore the theoretical value for the contrast ratio is 'infinity' which is not attainable. LCD and LED TVs for example has a backlit LCD screen, and for a black object to be shown on screen, the LCD element has to shut off the backlight completely. But with the backlight on all the time, some light escapes through the LCD element and reaches the screen. Since there is some light falling on the black objects on the screen, the Contrast Ratio of an LCD / LED TV is always less than that of a Plasma TV. This is because the Plasma elements light up pixel by pixel, and there is no need to have backlight illumination. Modern LCD TV, with many innovations have improved their contrast ratio to a very high level and the pictures are great now, almost as good as that of the Plasma TV.

It should be mentioned here that there are no industry standards for Contrast Ratio, and the figures quoted by manufacturers are not a reliable scale for comparison of the Contrast Ratio. To add to this confusion, there two types of Contrast Ratios - Static and Dynamic Contrast Ratio. So if you have to compare Contrast Ratio of different TV models, then a reliable comparison can only be made with models from the same manufacturer - Sony to Sony, Samsung to Samsung, LG to LG, and so on.

TV Audio Power Output

The higher the figure the better. LCD, LED and Plasma TV are generally not fitted with good speakers, because to have the speakers inbuilt means that the TV becomes bulkier. People who buy the expensive flat screen TV usually prefer to fix an audio amplifier and larger speakers.

TV Connections

Once you bring your TV home, it has to be connected to your video source. This can be a difficult task for someone with no idea of the different cables. We have a dedicated page on TV connections and there are two videos on that site explaining about the connections and about the connecting cables. If you do not know how to hook up your TV to the Cable TV box or DTH box or DVD player have a look at our page by clicking on TV Connections.