Before we had HDTV and widescreen televisions, all TVs were somewhat square in shape. Many still are. Most people still have standard definition TVs in their homes. The aspect ratio of these TVs is 4:3, which means that the TV is 4 units wide for every 3 units high. So, an SDTV screen that is 40 inches wide will be 30 inches high.
These screens are fine for regular SDTV, but widescreen movies pose a problem. The movie image is much wider than the TV screen. It won't fit without some modification.
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Figure 1 - Relating aspect ratios to each other
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Even if you have a widescreen television, you may still see black bars at the top and bottom of your screen when you view some movies. This is because some movie aspect ratios are wider than even wide screen TVs. In order to allow you to see the whole image from left to right, the whole picture needs to be shrunken down a bit to avoid cutting off the edges on a TV screen.
So, why are many movies widescreen, anyway? In short, so they could compete with TV. Let's look at a bit of widescreen history.
In the early years of cinema, movies used a 1.33:1 (4:3) aspect ratio. This was know as "Academy Ratio". Other than a few odd exceptions, people watched movies on a somewhat square format. When TV was invented in the 1930's, they used the same ratio since it was familiar to most people.
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Figure 2 - The 2.35:1 Aspect Ratio
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The problem is, by the 1950's, people were staying home a lot more often and watching TV. This meant fewer people were going out to see movies. The film industry realized they needed a gimmick. They needed a way to separate themselves from TV in a way that couldn't be properly reproduced at home.
The studios attempted to wow audiences with 3D, but audiences generally didn't take to wearing the glasses. Instead, the studios decided to make the movies bigger - literally. The introduction of Cinemascope in 1953 gave audiences a view that, at a 2.35.1 aspect ratio (Figure 2), was roughly twice as wide as a TV image. Even movies that didn't use the Cinemascope aspect got wider, too. In the US, many movies were (and still are) shot in a 1.85:1 aspect ratio. In Europe, 1.66:1 became popular.
For a while, this wasn't too much of a problem. Movies were mostly show in theaters where wider screens were available and television programs were shot in a 4:3 aspect ratio to fit TV screens at home. However, in the 1970's everything changed.
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Figure 3 - Cropping for TV
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After unsuccessfully attempting to sue the VCR out of existence, the movie companies realized they could capitalize on it instead. Home video was becoming a booming business and the studios found that additional revenue could be made off films be selling them on video tape. Now they could make money from both theater tickets and home video purchases. Of course, now the studios had a problem.
Since the studios worked so hard to make films essentially incompatable with TV, the home video market was a bit of a fly in the ointment. While there was money to be made there, the film aspect ratios were wider than that of a TV screen. The studios had a big question on their hands: How do you display an image that is wider than the screen you are using? To get around the problem, you have a few choices available.
One way to get around the problem is to crop the sides of the image. Of course, this creates another problem: you lose part of the image at either side.
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Figure 4 - Cropping to 16:9
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Take a look at the widescreen sample above (Figure 1). The widest portion (red) shows the outer reaches of a 2.35:1 image, which is the aspect ratio of many movies. Note how much more you see on either side compared to the 4:3 cropped image (Figure 3) shown above. That same image has been placed inside the widescreen sample to illustrate how much image area is lost to cropping. It's actually quite a bit. Compare that to the same widescreen image cropped to 16:9 (Figure 4, to the right). While a decent amount of image is still lost, the cropping is much less severe.
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Figure 5 - Panning and Scanning a movie
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Because you may miss some elements off screen when a widescreen image is cropped to 4:3, movies formatted this way often use a process called "Pan and Scan". This actually slides the image left and right to keep the action in the viewable area of the screen (Figure 5).
An example of this technique is in the movie "A League of Their Own". In the movie, there are several moments where characters at the left and right sides of the widescreen image talk to one another. One character or the other would have to be left offscreen if the image was left static. Instead, artificial left and right camera pans are used to make sure each person is on screen when they speak.
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Figure 6 - 2.35:1 Letterboxing on a 4:3 TV
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Another method is to use Letterboxing. This shrinks the whole image down so you can see it fully from left to right. However, because it's now not as tall as the TV screen, black bars will appear at the top and bottom of the image. This doesn't mean anything is getting cut off. In fact, it's actually the opposite. You're seeing everything that was shown in the theater. However, it does give he appearance that the image is being cropped.
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Figure 7 - 2.35:1 Letterboxing on a 16x9 widescreen TV
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Even on a widescreen TV, the 2.35:1 aspect ratio will still show small bars on the top and bottom of the screen. Despite being wider than a standard TV, widescreen TVs still aren't as wide as this theatrical aspect ratio. However, 1.85:1, another popular film ratio, often displays with little or no black space above and below the image on a widescreen TV.
Of course, the downside of this method is it can create a very small image on a small 4:3 TV. For some people, this can make it hard to watch. This is one reason why Full Screen (cropped left and right) versions are often available.
Both of the above methods of formatting movies for TV are compromises. Both make viewing movies on a standard TV a less than optimal experience. While you aren't always missing much with a cropped image, some directors do an excellent job of framing for widescreen. This means the entire feel of a shot can be altered by cropping. Sometimes it simply makes the framing feel too cramped. Other times the flow of the scene is interrupted by an artificial cut or pan to get everything in the frame.
There is yet another way to make a movie image fit a TV screen. This is through a process called "Open Matte".
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Figure 8 - Open Matter formating for a 16x9 TV.
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Some films are shot with a lot of excess space at the top and bottom, then cropped for the widescreen presentation in the theater. Using this method, a director can adjust the exact shot well after shooting has wrapped. This extra space isn't meant to be seen, but it can be useful for the home video market.
By "unmasking" the image and showing that extra space, people with 4:3 TVs can enjoy seeing the entire image left to right without black bars at the top and bottom.
Take a look at Figure 8, to the right. Notice the image area is the same left to right as the letterboxed image in Figure 7, above. However, the matte has been opened up at the top to reveal the extra image area. While it does change the framing of the shot, it prevents the edges of the image from being cropped without the need for letterboxing.
Of course, not all films have this "Open Matte" capability. A true Cinemascope image won't have that extra image area. In this case, letterboxing is the only way to see the entire movie image on your screen.
