The aspect ratio on the television screens
For Digital Future | October 2, 2008
The aspect ratio of a TV screen is basically a measure of the length (horizontal) in relation to their height (vertical).
A traditional television has a screen aspect ratio of 4:3. This means that there are four units long for every three high. This would be for example, a screen of 40 inches long by 30 centimeters in height.
In the case of widescreen televisions such as HDTV, the aspect ratio of the screen is 16 units long for every 9 units of height. Putting an example, 60 centimeters long, we have a height of 33'75 inches. A screen 16:9 therefore has a greater display of the image that a 4:3 aspect ratio and is better suited to human vision, in which the horizontal is much greater than the vertical. The 16:9 format allows movies originally filmed in widescreen and in widescreen display with greater precision.
With more and more programming available in widescreen formats, owners of television sets 4:3 has been seeing a growing number of TV programs and DVD movies with black bars at the top and bottom of their screens (known as Letterboxing). This is not because of the emergence of 16:9 screens, but that is because most of the films made after 1953 were (and still are) filmed in various widescreen formats, such as Cinemascope, Panavision, Vista -Vision, Technirama, Cinerama, or other type of widescreen movies.
On the screens of 4:3, to show a movie format with a "wide" is used the bread-and-scan or Letterboxing. The pan and scan is the method by which a film clip shot at widescreen, to fill a screen less wide, as the TV. This process changes the aspect ratio of the image without deform, which often leads to ruin the composition. Several film directors and enthusiasts do not agree with this technique because it eliminates 45% of the image, and you can change the original vision of the film. Before this technique was widely used, but as you can see in the example, the loss of image is very high because with the bread-and-scan only we stayed with the 4:3 box and despised the rest of the picture. This process requires a great dedication to get the best result possible.
The alternative to the pan and scan is as I have commented on Letterboxing, another practice of turning films shot in widescreen video to other formats, but unlike the bread-and-scan, preserving the aspect of the picture. As the 4:3 screen is less wide, it should add black bars top and bottom of the picture (more precisely calls Mattes) to adjust the length of the original image on the screen. Thus, the height of image used in the display will depend on the aspect of the original recording of the film although there is an obvious problem with the loss of space used on the screen, so we will see smaller images of what it should be.
Now you'll likely have a high resolution display at home (HDTV) so when we see an old home video recording made at 4:3 we'll see an image like this:
In this case adjusting the height of the image with that of the screen, preserving the relationship of image, and add the vertical black bars to fill the remainder of the screen.
Detailing a bit more reason to use screens with 16:9 format, we can say that these securities are designed by H. Kerns Powers when no one was creating videos in this format. The popular formats in 1980 were 4:3, 15:9, 1.85, 2.20 i 2.35. Powers discovered that all these aspect ratios fit within an outer rectangle of 1.78:1 and removing the excess of 0.02 to 1.78 × 9 operation, we see that they all share a rectangle inside of 16:9.
The next picture shows the various formats and demonstration of the theory of Powers:
The colors are: Red: 4:3, Green: 3:2, Blue: 16:9, Yellow: 1.85:1, Lila: 2.39:1
While the 1.78:1 format was originally a compromise, the popularity of HDTV broadcast in 1.78:1 has solidified this format.
I hope that now you may be able to explain why black bars on their television screens. Another day we will talk about the formats used in recording movies and it does not use the 16:9.
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