Anamorphic vs Letterbox question

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Anamorphic vs Letterbox question

Postby Chaos Angel » Mon Jul 28, 2003 12:16 am

Just a quick question. Does anyone know why the black bars are larger in letterboxing than they are in anamorphic video that is sized for standard-resolution TVs? I would imagine that they'd be the same size, is why I ask, and I'm curious.
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Postby Castor Troy » Mon Jul 28, 2003 2:40 am

All I can say is that certain movies just want to show more of the left and right sides than others.
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Postby klinky » Mon Jul 28, 2003 3:45 am

Well it's not actually "anamorphic" that makes that happen. It's rather the series or movie was designed for the big screen or your TV. Films usually have a much wider aspect ratio than TVs do. So you'll have to shrink it down and put letterboxes on the top and bottom.

Anamorphic is the concept of taking a film(whatever resolution it is) and blowing it up to the full 720x480 DVD resolution. This is done so that all bitrate is spent on the image and not on black boxes on the top or bottom. It is then later resized on the fly to fit on your TV.
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Re: Anamorphic vs Letterbox question

Postby koronoru » Mon Jul 28, 2003 9:17 am

Chaos Angel wrote:Just a quick question. Does anyone know why the black bars are larger in letterboxing than they are in anamorphic video that is sized for standard-resolution TVs? I would imagine that they'd be the same size, is why I ask, and I'm curious.


Because anamorphic video is wider than TV video. It's closer to the movie aspect ratio already, so there's less adjustment necessary.

Your TV has an aspect ratio of 1.33 (4:3). Movies vary, but typically have an aspect ratio of 2.25. If you show a movie in letterbox format on a TV screen and you size it so the movie is the same width as the screen, then it will cover 1.33/2.25=0.591 fraction of the height of the screen; you need your black bars to cover roughly 41% of the screen.

Anamorphic video has an aspect ratio of 1.78 (16:9). If you show that same 2.25 movie sized to be the same width as an anamorphic screen, then it will cover 1.78/2.25=0.789 fraction of the height of the screen; you need black bars to cover roughly 21% of the screen, or about half as much as for letterbox.
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Re: Anamorphic vs Letterbox question

Postby koronoru » Mon Jul 28, 2003 9:19 am

koronoru wrote:Anamorphic video has an aspect ratio of 1.78 (16:9).


Clarification: Klinky's response suggested that anamorphic video could have any aspect ratio. That's true, but I'm pretty sure that's not what the original poster meant, because if the video really were the same aspect as the original movie, then there wouldn't be any black bars at all. The original question only makes sense assuming we're talking about the very popular 16:9 anamorphic format.
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