Editing 70 mm film (section)

== History ==
[[File:70mm-Film.jpg|thumb|Faded vintage 70&nbsp;mm positive film with four magnetic strips containing six-channel stereophonic sound]]
Films formatted with a width of 70&nbsp;mm have existed since the early days of the motion picture industry. The first 70&nbsp;mm format film was most likely footage of the [[Henley Regatta]], which was projected in 1896 and 1897, but may have been filmed as early as 1894. It required a specially built projector built by [[Herman Casler]] in [[Canastota, New York]] and had a ratio similar to full frame, with an aperture of {{convert|2.75|in|mm}} by {{convert|2|in|mm}}. There were also several film formats of various sizes from 50 to 68&nbsp;mm which were developed from 1884 onwards, including [[Cinéorama]] (not to be confused with the entirely distinct "[[Cinerama]]" format), started in 1900 by [[Raoul Grimoin-Sanson]]. In 1914 the Italian [[Filoteo Alberini]] invented a panoramic film system utilising a 70&nbsp;mm wide film called Panoramica.<ref>"Preserving Wide Film History" Grant Lobban, Journal of the BKSTS Vol 67 No.4 April 1985</ref>

===Fox Grandeur===
{{main|70&nbsp;mm Grandeur film}}
In 1928, William Fox of the [[Fox Film Corporation]], in personal partnership with Theodore Case as the Fox-Case Corporation, began working on a wide film format using 70&nbsp;mm film which they named [[70 mm Grandeur film|Grandeur]]. Cameras were ordered by Fox-Case from Mitchell Camera Corp, with the first 70&nbsp;mm production cameras, designated as the Mitchell Model FC camera, delivered to Fox-Case in May 1929. This was one of a number of wide-film processes developed by some of the major film studios at about that time. However, due to the financial strains of the Great Depression, along with strong resistance from movie theater owners, who were in the process of equipping their theaters for sound, none of these systems became commercially successful. Fox dropped Grandeur in 1930.<ref>"Preserving Wide Film History" Grant Lobban, ''Journal of the BKSTS'' Vol 67 No.4 (April 1985)</ref>

===Todd-AO===
[[File:65 mm film (5-70).svg|thumb|right|upright=1.42|Todd-AO / Panavision (5-perf) 65 mm negative frame dimensions; the ''Ultra Panavision'' 1.25× anamorphic process is represented by the distorted circle.]]
{{main|Todd-AO process}}
Producer [[Mike Todd]] had been one of the founders of [[Cinerama]], a wide-screen movie process that was launched in 1952. Cinerama employed three 35&nbsp;mm film projectors running in synchronism to project a wide (2.6:1) image onto a deeply curved screen. Although the results were impressive, the system was expensive, cumbersome and had some serious shortcomings due to the need to match up three separate projected images. Todd left the company to develop a system of his own which, he hoped, would be as impressive as Cinerama, yet be simpler and cheaper and avoid the problems associated with three-strip projection; in his own words, he wanted "Cinerama out of one hole".

In collaboration with the [[American Optical Company]], Todd developed a system which was to be called "[[Todd-AO]]". This uses a single 70&nbsp;mm wide film and was introduced with the film ''[[Oklahoma! (film)|Oklahoma!]]'' in October 1955. The 70&nbsp;mm film is perforated at the same pitch (0.187 inch, 4.75&nbsp;mm) as standard 35&nbsp;mm film. With a five-perforation pull-down, the Todd-AO system provides a frame dimension of 1.912 inch (48.56&nbsp;mm) by 0.87 inch (22.09&nbsp;mm) giving an aspect ratio of 2.2:1.

The original version of Todd-AO used a frame rate of 30 per second, 25% faster than the 24 frames per second that was (and is) the standard; this was changed after the second film – ''[[Around the World in 80 Days (1956 film)|Around the World in 80 Days]]'' - because of the need to produce (24 frame/sec) 35&nbsp;mm reduction prints from the Todd-AO 65&nbsp;mm negative. The Todd-AO format was originally intended to use a deeply curved Cinerama-type screen but this failed to survive beyond the first few films.<ref>"In the Splendour of 70&nbsp;mm Part 1" Grant Lobban, Journal of the BKSTS Vol68 No.12 December 1986</ref> However, in the 1960s and 70s, such films as ''[[The Sound of Music (film)|The Sound of Music]]'' (which had been filmed in Todd-AO) and ''[[Patton (film)|Patton]]'' (which had been filmed in a copycat process known as Dimension 150) were shown in some Cinerama cinemas, which allowed for deeply curved screens.<ref>{{cite web|url=http://cinematreasures.org/theaters/4784|title=Atlanta Theatre|work=Cinema Treasures|access-date=1 December 2015}}</ref>

Todd-AO adopted a similar multi-channel magnetic sound system to the one developed for [[Cinemascope]] two years earlier, recorded on "stripes" of magnetic oxide deposited on the film. However Todd-AO has six channels instead of the four of Cinemascope and due to the wider stripes and faster film speed provides superior audio quality. Five of these six channels are fed to five speakers spaced behind the screen, and the sixth is fed to surround speakers around the walls of the auditorium.

===Panavision and the 65/70 mm format===
{{main|Super Panavision 70|Ultra Panavision 70}}
Panavision developed their own 65/70&nbsp;mm system that was technically compatible and virtually identical to Todd-AO.  Monikered as [[Super Panavision 70]], it used spherical lenses and the same 2.2:1 aspect ratio at 24 frames per second. Panavision also had another 65&nbsp;mm system, [[Ultra Panavision 70]], which sprang from the [[MGM Camera 65]] system they helped develop for MGM that was used to film ''[[Raintree County (film)|Raintree County]]'' and ''[[Ben-Hur (1959 film)|Ben-Hur]]''.  Both Ultra Panavision 70 and MGM Camera 65 employed an anamorphic lens with a 1.25x squeeze on a 65&nbsp;mm negative (as opposed to 35&nbsp;mm [[CinemaScope]] which used a 2× compression, or 8-perf, horizontally filmed 35&nbsp;mm [[Technirama]] which used a 1.5× compression).  When projected on a 70&nbsp;mm print, a 1.25× anamorphic projection lens was used to decompress the image to an aspect ratio of 2.76:1, one of the widest ever used in commercial cinema.