Books can be (and have been) written on the history of aspect ratios in motion pictures. But let's keep this basic.
Fifty years ago, studios were going broke because theater patrons were staying home to watch TV. So they embarked on a campaign to give theatergoers something they couldn't get at home. That's when movies got wider.
Today, the vast majority of films are framed for one of three common shapes or "aspect ratios":
1.66:1: This is much more common than Europe than in the U.S. When a film is transferred to DVD in this aspect ratio, it will have very small black bars on a standard 1.33:1 TV screen.
1.85:1: Very common in the U.S. Films transferred to DVD in this ratio will have somewhat larger black bars, but still less than a third of the available space on a standard TV screen.
2.35:1: This very wide aspect ratio used to be found primarily in epic adventures, but today it has become common for all sorts of films, even intimate domestic dramas like the 2001 Oscar contender In the Bedroom. Films on DVD in this aspect ratio will have very large black bars, roughly 40% of the available display area.
There's another aspect ratio you may have heard about, 1.78:1. It's not from film. Instead, it's the official aspect ratio for high-definition TV. You may know it by its other designation: 16:9. DVDs have a special connection with the 16:9 format, which is the next subject to address.
What are "anamorphic" DVDs?
Many widescreen DVDs feature what's called "anamorphic" enhancement. You can't always tell by looking at the DVD cover, because the studios don't have a standard format for listing this feature. Often it's referred to as "enhanced for 16:9". Sometimes you'll see "enhanced for widescreen TVs". And often there's no mention of it at all (e.g., most DVDs from Columbia Tristar).
The following explanation of anamorphic DVD is one from the vaults. It was written by former HTF admin Rob Gillespie, and it's the best short explanation of the subject I've ever seen.
Rob's explanation talks about "scan lines". "Scan lines" are what make up the picture on your TV screen. Your TV draws 480 visible scan lines across the screen 30 times every second to "paint" the video picture you see. When films are presented in widescreen, some of those lines have to be used to draw the black bars, which is something of a waste. DVDs offer a way to make better use of those scan lines, and that's what anamorphic enhancement is all about:
An anamorphically enhanced DVD spreads the image over more scan lines, increasing the resolution. Where do these extra lines come from? Well, on a normal letterboxed transfer, they are the space used for the black matting bars. If you play such a transfer on a standard 4:3 TV, the image appears tall and thin.
Ok so far?
When an anamorphic DVD is played back, obviously the image needs to be restored to it's correct proportions. There are three ways this can be done.
On a standard 4:3 TV, the 'squeeze trick' can be done. This consists of entering the service mode and reducing the vertical size of the viewable picture until the proportions are correct. You're basically doing the same adjustment that's possible on computer monitors. On most European and very few American TVs, there is a proper '16:9' mode which does the squeeze trick at the touch of a button.
On a 4:3 TV without doing the 'squeeze', the DVD player must be set to '4:3' within it's setup menu. This forces the player to 'downconvert' the anamorphic image by removing some of the scan lines. This plays the image back at the correct proportion, but obviously loses some of the original resolution. It can also introduce unwanted artifacts, especially on scrolling credits etc.
On a widescreen TV, if the correct screen mode is used, the anamorphic image is stretched laterally, restoring it to the correct proportions.
The aspect ratio of the film itself is completely independent to the above. On an anamorphic DVD, the AR can be anything above 1.78:1.
A normal 'widescreen' DVD presents the film in it's proper aspect ratio (eg. 1.85:1, 2.35:1 etc) but does not include the anamorphic enhancement. This means the image is spread over fewer scan lines, dropping the resolution somewhat. This will play back fine on a normal TV without adjustment, but will obviously have the 'black bars' top and bottom depending on the AR. If played on a widescreen TV, the set must be put into the correct picture mode (on Sony's, it's usually 'Zoom', but varies with other makes).
For further information, try here:
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