For a long period of time television sets have been designed with a 4:3 aspect ratio. That is, the width of a television set is 4/3 times its height. The 4:3 aspect ratio is often referred to as the standard format. In the United States, these sets are able to receive National Television System Committee (NTSC) signals and the video data encoded in NTSC signals are in the 4:3 aspect ratio. Most of the television shows produced are recorded in a 4:3 aspect ratio.
Movies produced for theater exhibition use a widescreen format. The most common widescreen format utilizes a 16:9 ratio. High definition television sets are often produced in a 16:9 ratio instead of the 4:3 ratio. High definition television signals also carry video data that are in a 16:9 ratio. A number of television shows are now produced using a widescreen format.
These high definition television sets are also capable of displaying standard video. However, because there is extra horizontal space on a television with a 16:9 ratio compared to a 4:3 output, black vertical bars are often added to the left and right of the displayed video. By stretching a 4:3 image horizontally to fully utilize a 16:9 display, the result would often be people and other objects appearing unusually short and stocky.