Aspect ratios are one of the more confusing parts of video, although they used to be simple. That's because television and movie content were all about the same size, 4:3 (also known as 1.33:1, meaning the picture is 1.33 times as long as it is high). The Academy (as in, "I'd like to thank the Academy") Standard before 1952 was 1.37:1, so there was no problem showing movies on TV.
However, as TV began to cut into Hollywood's take at the theater, the quest was on to differentiate theater offerings from TV. Thus, innovations such as widescreen film, Technicolor, and even 3-D were born.
Widescreen film was one of the innovations that survived and has since dominated the cinema. Today, you tend to find films in one of two widescreen aspect ratios:
- Academy Standard (or "Flat"): Has an aspect ratio of 1.85:1.
- Anamorphic Scope (or "Scope"): Has an aspect ratio of 2.35:1. Scope is also called Panavision or CinemaScope.
HDTV is specified at a 16:9, or 1.78:1, aspect ratio.
Viewing widescreen images
If your television isn't widescreen and you want to watch a widescreen film, you have a problem. And the industry powers that be have come up with two solutions (other than "go out and buy a widescreen display").
The most common approach in the past has been what's called Pan and Scan. For each frame of a film, a decision is made as to what constitutes the action area. That part of the film frame is retained, and the rest is lost. What's left is usually a fraction of the main frame, sometimes as little as 65 percent of it, and this can often leave out the best parts of a picture. Imagine some of the scenes from Gunfight at the O.K. Corral with the two gunslingers at each end of the picture. One of the gunfighters would disappear from the screen in Pan and Scan.
The second (and growing more popular) approach is to display the original full image on the TV set without filling the whole screen. When watching content formatted for a widescreen TV (1.85:1, 2.35:1, and so on), you see black bars at the top and bottom of the image. This technique is known as letterboxing (after the effect of seeing an image through an open mail slot in a door). Conversely, when watching content formatted for TV (4:3) on a widescreen TV, you see black bars on the left and right of the images. This is known as windowboxing.
A tight squeeze
An obvious problem with viewing widescreen images on a normal 4:3 TV is that the image doesn't use all 480 scanning lines of the screen. Some of those 480 lines get used just to draw black bars instead of drawing video you actually watch. (Some 4:3 TVs use a technique called anamorphic squeeze to eliminate this issue.) This waste of lines yields lower resolution, something that anamorphic formats attempt to resolve. Also known as 16:9 Enhanced, Widescreen Enhanced, or Enhanced for 16:9 Televisions, anamorphic presentation squeezes the image horizontally until the image fills the 4:3 frame. If you look at an anamorphic picture on a 4:3 screen, the picture appears somewhat distorted because everything is compressed, but the full 480 lines of content are retained. Luckily, when you tell your DVD player you have a 4:3 screen, it puts the anamorphic image back into a letterbox. When played through a 16:9 player, the original width is presented, while maintaining the full 480 vertical lines of resolution.
Now on DVD
Many DVDs have both a Pan and Scan and a widescreen format (either letterboxed or anamorphic) on one DVD. Because including both versions creates an added expense to the studios, some DVDs ship with just one format onboard, and some titles actually have different formats on different discs. Be sure to check before you buy a disc if this is important to you.
As an interesting note, there are a few examples (Pixar's Finding Nemo being the most famous) where movie producers have specially modified their content to have different widescreen and 4:3 versions - so the folks with 4:3 displays aren't robbed of part of the image while still filling their screens.
