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Old August 25th, 2008, 09:39 AM   #1
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Actual Cinemascope Aspect Ratio

I'm not sure if this topic belongs in this thread. Could anyone here shed the light on why there are a number of cinemascope widescreen ratios e.g. 2.35:1, 2.38:1 and 2.40:1 etc. instead of one single standard in used for the digital media today? While the "narrower" film-originated widescreen standard seems to be just one, 1.85:1. I've been a little confused since first going widescreen in my video career some years ago.

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Old August 25th, 2008, 02:21 PM   #2
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There were a number of anamorphic formats competing with each other over the years, together with 65mm (70mm projection) and each process was slightly different. It was a case of manufacturers coming up with products without a great standards committee deciding things in advance.

There is more than one flat widescreen aspect ratio apart from 1.85, there's also the European widescreen 1.66 as found on Super 16 cameras. Video has settled on 16:9, which is more or less a split between the two film flat widescreen aspect ratios.

Aspect ratio (image - Wikipedia, the free encyclopedia)
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Old August 25th, 2008, 04:08 PM   #3
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Or to quote an engineer friend of mine - "That's the great thing about 'standards' - you have so many to choose from."
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Old August 25th, 2008, 08:33 PM   #4
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Thanks, Brian. It's fortunate that the majority of work I'm involved in has a solid single standard in the 1.78:1 or 16:9 digital HD ratio!

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Old August 29th, 2008, 09:08 PM   #5
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Spend a little time at one of my favorite websites: American WideScreen Museum - provided as a public service by Martin Hart

See this: Widescreen Museum - CinemaScope, Panavision, etc. Aspect Ratio
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Old August 30th, 2008, 10:02 PM   #6
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35mm 4-perf CinemaScope / anamorphic has traditionally had a constant squeeze ratio of 2:1. The reason the aspect ratio changed over time is due to the shape of the projector gate before the image is expanded by 2X by the anamorphic projector lens.

Originally CinemaScope planned to use 4-perf 35mm Full Aperture (silent) for the entire image, negative and positive, and run the sound in interlock on a separate mag, as Cinerama did. Since 4-perf 35mm Full Aperture is 1.33 : 1, putting a 2X optical squeeze in the image would result in a 2.66 : 1 image on the screen once unsqueezed (which happened to be Cinerama's aspect ratio more or less.)

However, it was decided before the first CinemaScope movie was even shot to put the soundtrack on the print. At first, they decided to put magnetic stripes on both sides of the print, which shaved some of the image area off on both the left and right sides. To make even more room for the magnetic stripes, the perfs in the print themselves were made smaller ("CS" perfs). With the sides trimmed off by using a less wide gate in projector, the image when expanded by 2X was only 2.55 : 1 instead of 2.66 : 1. And the composed image was centered on the negative between the two rows of perfs.

But eventually they decided to go back to the traditional optical soundtrack on normal perfed print stock, where the projector gate cropped only the left side to make room for the optical soundtrack. So the unsqueezed 2X image was now only 2.35 : 1 (divide by 2 to get the real aperture) and offset to the right on the negative, as it is on 1.85 and Academy sound movies.

This is one reason why contact prints of earlier CinemaScope movies like "20 Thousand Leagues Under the Sea" look off-centered -- the image is centered on the negative and the print, but the projector aperture is off-centered to hide the optical soundtrack added to the left edge.

So the projected ratio was 2.35 : 1 until the early 1970's when it was decided to make the projector aperture a little shorter top to bottom to hide frameline negative splices better -- the frames are so close together in CinemaScope that any poor splicing causes visible white flashes at the top or bottom of the projected image. So making the framelines thicker by shortening the height of the gate helped hide that better.

Shortening the height of the projector gate shaved the image vertically so the final aspect ratio was almost 2.40 : 1 (2.39... : 1). The aperture dimensions were changed again in the early 1980's but the final aspect ratio is still around 2.39 : 1 once unsqueezed by doubling the width of the image optically by 2X.
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Old August 31st, 2008, 12:34 AM   #7
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The matted widescreen projector aperture has also been in flux over the years -- obviously if it weren't 1.85, we'd call it something else.

It's been 1.85, 1.66, and 1.75 for decades, different sized projector masks, but gradually 1.85 has become dominant, though a few European filmmakers still use 1.66.

Basically in 1953 or so, the studios started cropping their 1.37 Academy movies to widescreen by using a special mask in the projector gate, and around the same time, started telling cameramen to frame their movies with this cropping in mind. Universal and MGM proposed 1.85 masking, Disney wanted 1.75, and Paramount wanted 1.66, and it was pretty unstandardized for years, you had no idea what mask a movie theater was going to use. Eventually 1.85 became the defacto standard more or less, 1.66 was more popular for awhile in Europe.
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Old September 1st, 2008, 09:08 AM   #8
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David, thanks a lot for taking your time clarifying this to me and I'm sure to others as well. Your depth of knowledge is a valuable asset for this forum. It would take me a very long time to figure this out were it not for you explanations.

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