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70 mm film (or 65 mm film) is a high-resolution motion picture film format. As used in camera, the film is 65 mm wide; for projection 2.5 mm are added along each outer side of the perforations for magnetic strips holding six tracks of surround sound, although in truth, the magnetic sound system is rarely used anymore. Each frame is five perforations tall, with an aspect ratio of 2.20.
With the introduction of "Todd-AO", 65 mm/70 mm became popular during the 1950s for the wide screen, sharp picture and, most importantly, high quality sound. The advent of low-grain film stocks and availability of digital soundtrack systems for less expensive and more widely projectable 35 mm film lead to a decline in use of this expensive format in the 1990s. Lawrence of Arabia is a well-known film in 70 mm format; the clarity of its picture is apparent in theaters, though much less so on VHS or DVD.
There is a subset of 70 mm film known as Showscan, in which the picture is captured and shown at 60 frames per second, which can have beneficial effects on qualities like image strobe, flicker, and grain. It never caught on with mainstream cinema, and is primarily used for theme park simulation rides.
A horizontal variant of 65 mm/70 mm, with an even bigger picture area, is used for the high-performance IMAX and Omnimax format. The Dynavision and Astrovision systems are each systems which use slightly less film per frame and vertical pulldown to save print costs while being able to project onto an IMAX screen. Both are rare, Astrovision more or less exclusively occupying only Japanese planetariums.
Steven Spielberg's Close Encounters of the Third Kind was mainly shot on 35 mm film, but the effects sequences were shot on 70 mm film. Special effects man Douglas Trumbull (who later invented Showscan) decided to do this so that there would be no loss of quality which might subconsciously "warn" moviegoers that an effects sequence coming up.
Starting in the late 1950s until the mid-1990s, many 35 mm films were converted onto 70 mm prints for premiere showings in large cities or venues which could accompany the format. Often this was not just for issues of image size, but more because of the six magnetic sound tracks available (versus two optical sound tracks on 35 mm) with 70 mm prints. Since the introduction of DTS, SDDS, and Dolby Digital, 70 mm lost this advantage, and a significantly lower number of 70 mm prints typically are struck today.
Technical Specs
Standard 65 mm (5/70) (Todd-AO, Super Panavision)
- spherical lenses
- 5 perforations per frame
- 12.8 frame/ft (42 frame/m)
- vertical pulldown
- 24 frames per second
- camera aperture: 2.066 by 0.906 in (52.48 by 23.01 mm)
- projection aperture: 1.912 by 0.816 in (48.56 by 20.73 mm)
- 1000 feet (305 m), about 9 minutes at 24 frame/s = 10 pounds (4.54 kg) in can
Showscan
Same as Standard 65 mm except
IMAX (15/70)
- spherical lenses
- 15 perforations per frame
- horizontal pulldown, from right to left (viewed from base side)
- 24 frames per second
- camera aperture: 2.772 by 2.072 in (70.41 by 52.63 mm)
- projection aperture: at least 0.80 in (20 mm) less than camera aperture on the vertical axis and at least 0.016 in (0.4 mm) less on the horizontal axis
Omnimax
Same as IMAX except
- special fisheye lenses
- lens optically centered 0.37 in (9 mm) above film horizontal center line
- projected elliptically on a dome screen, 20 degrees below and 110 degrees above perfectly centered viewers
Dynavision (8/70)
- fisheye or spherical lenses, depending on if projecting for a dome or not
- vertical pulldown
- 24 or 30 frames per second
- camera aperture: 2.080 by 1.480 in (52.83 by 37.59 mm)
Astrovision (10/70)
- vertical pulldown
- normally printed from an Omnimax negative
- projected onto a dome
- almost exclusively in use only by Japanese planetariums
- the only 70 mm format without sound, hence the only with perforations next to the edges
Famous 65 mm/70 mm films
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