From: utzoo!decvax!harpo!eagle!mhuxt!mhuxj!mhuxa!houxm!hogpc!houti!ariel!vax135!cornell!uw-beaver!tektronix!tekecs!davew
Newsgroups: net.movies
Title: Re: 3-D Movies
Article-I.D.: tekecs.1101
Posted: Thu May 12 12:01:28 1983
Received: Thu May 19 05:26:26 1983
References: uw-beave.581


    During the early 1950's the motion picture business tried all sorts
of new film formats to try and lure the public away from the boob tube.
One of the approaches was the wide screen. Among the contending
processes was Cinerama, a system that used 3 35mm projectors running
simutaneously to put a large picture on the screen. The normal pull
down (i.e. picture height) for 35mm film is 4 sprocket holes, Cinerama
used 6 meaning that each film ran at 1.5 times normal speed or 135 feet
per minute instead of the usual 90 fpm. The Cinerama format also used
the 3 mm optical sound track area for picture. The sound was carried on
a separate 35mm magnetic film with 7 audio channels and a control
track. This meant that the Cinerama format ate up 6 times the film of
the standard format. Because 3 images were projected on the screen at
once (left,center,right) there was some over lapping vertical lines on
the screen where the images overlapped as well as some jitter problems.
As the technique was improved these problems were minimized.  Since
theaters had to be specially outfitted for this process and the screen
size was so huge only large theaters in some of the larger metro areas
were equipped for it.
 Another process used an anamorphic lens to squeeze the horizontal
field onto a standard 35mm format film. On projection a similar lens
was used to expand the image to the wide screen format. Aspect ratios
of 1.67:1 to as large as 2.75:1 were used. Some of the trade names were
Cinemascope (20 th Century Fox), VistaVision (Paramount) and Superscope
(Those same wonderful people who now bring you Marantz hi-fi). For road
show engagements 4 magnetic sound tracks were added to the print, 3
audio and one control track so that the sound could be switched between
various speakers throughout the theater.
   Some 70mm formats were also tried, among them Todd AO.
  3-D movies used two images slightly offset from one another to gain
the 3-D effect.  A special camera mount was used which consisted of two
35mm cameras pointed at each other with two mirrors in between. The
mirrors were adjustable for shooting objects near or far from the
camera. The mirrors reflected the images into the two cameras.
 The two films were run back at the same time through 2 projectors
using Polaroid polarizers. The audience wore Polaroid glasses to filter
the right and left images to the proper eye.
		    Dave Williams
		    Tektronix ECS