Is's just the width to height ratio of an image. Until today most TVs has been 4/3, but now more and more are turning over to 16/9.1) Letterbox
Here all of the film is visible and in it's original aspect ratio, but the vertical resolution is not good. Many 16/9 TVs can use the active region here and calculate one extra line for every 3 lines in order to get maximum vertical resolution. Some actual examples of what letterboxing looks like.
2) Movie Compress
The film is compressed horizontally to fit into the 4/3 screen. Well, people really look strange here. Clint Eastwood is not fat, but he is certainly not that skinny. On some films one use more compression on the sides. This makes objects change shape as they move over the screen. Many 16/9 TVs can "uncompress" compressed emissions so that the film will get it's original aspect ratio back. Some new 4/3 TVs can also transform compressed movies into a letterbox format as this is much more natural to watch.
3) Pan & Scan
This is what you will see with most films on videotape. Information on the sides is cut off and can't be restored again. Apart from not having an natural aspect ratio the film is by many videophiles seen as destroyed. A film is a piece of art and some scene may have been as carefully composed as a painting. Cutting of parts of it is no less than barbarism. And BTW you will not be able to see the gangster crawling in from the right before he is close to the center of the screen.
Or you could get a 16/9 TV
This is the aspect ratio more and more films will have on DVD and also in future digital broadcast formats. As indicated above with letterboxed movies the black bars will be smaller and the TV will calculate 1 extra line for each 3 line of image information. This will be done using technology similar to that used with expensive linedoublers. This will give better image quality than on a 4:3 TV, but not as good as if all 4 of the lines were actual information. If you have a film formatted for 16:9 or "anamorphic" then the TV don't have to calculate these extra lines.
For both 4/3 and 16/9 TVs one just measure the diameter. When comparing the 2 formats for a TV with the same diameter one will see that a widescreen version is bigger horizontally, but smaller vertically. As the natural field of vision has a shape closer to 16/9 than 4/3 the most important limitation is anyway the width of the TV. With the reduced height for widescreen it is in addition possible to sit nearer to the screen without seeing the lines and the TV will then cover even more of the visual field. A widescreen TV is simply much closer to seeing a movie in a cinema.If you want to compare the width or height for the 2 formats I have made the following chart. Along the diagonal is the size of the corresponding widescreen TV:
 For the same height as 4/3 |
||||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| 20.5" | 21.3" | 22.1" | 23.0" | 23.8" | 24.6" | 25.4" | 26.2" | 27.0" | ||
For the same width as 4/3 | 27.3" | 25" | ||||||||
| 28.3" | 26" | |||||||||
| 29.4" | 27" | |||||||||
| 30.5" | 28" | |||||||||
| 31.6" | 29" | |||||||||
| 32.7" | 30" | |||||||||
| 33.8" | 31" | |||||||||
| 34.9" | 32" | |||||||||
| 36.0" | 33" | |||||||||
Yes, this means that looking at a DVD movie letterboxed on a 4/3 display of 36" will give no bigger image than on a 33" widescreen. On the widescreen you will anyway get better resolution as there will be 33% more lines in use.
NB! Most brands tell you the diagonal of the entire tube and not of the actual image.
Films will also be made with wider images than 16/9, but the letterboxing or pan & scan that has to be done here is far less than what you will experience with the old 4/3 format.
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Last update 28. December 1998