Video Asylum

RE: 35mm

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This Post Has Been Edited by the Author

In Reply to: RE: 35mm posted by unclestu52 on August 20, 2007 at 13:27:31

You said "Film 35 MM had some space allowed for the audio soundtrack, thus limiting the full use of the 24 mm width." Actually the width of the frame is the 36mm dimension and cutting that down to 32 mm would give you a 4:3 ratio so you're probably right there. I hadn't considered the need to allow space for the optical soundtrack and just reeled off the 35mm negative frame size from my old still photography days.

You also said "In addition the standard TV signal has 525 lines by 720 which similarly yields a 1.37:1 ratio, although normally only 480 lines are displayed." It's what's displayed that counts and 720 pixels wide by 480 high is 3:2, not the 4:3 physical dimension ratio. You can use pixel ratios as an indication of image ratios on widescreen TVs because 1920/1080, 1366/768, and 1280/720 all basically come to 16:9, at least to roughly 2 decimal places, but that approach definitely doesn't work for standard definition screens in either NTSC (720 x 480 pixel display) or PAL (720 x 576 pixel display).

But then again, standard def displays weren't created with digital image formats in mind. If they'd bothered to think ahead we'd have been watching cinemascope movies in theatres in the 1920s and wide screen TV when TV was first introduced :-)

David Aiken

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