Popular Mechanics - August 1952



Sure enough, the World's Fair exhibit produced a startling three-dimensional effect. Out of it grew the gunnery trainer-and Cinerama, which is simply a photographic view of the scene as a human pair of eyes would see it. The picture Cinerama reproduces is 146 degrees wide and 55 degrees deep, close to that seen by two eyes, which cover at best some 165 degrees by 60 degrees. No lens known can cover such a field without distortion. Hence, the Cinerama camera has three 27-millimeter lenses set at 48-degree angles. Each takes a third of the picture's total width, exposing its own reel of 35-millimeter film housed in one of the three magazines that jut from the back of the camera.

The lenses are arranged on a mount like a three-section picture frame. The one in the center points straight ahead. Those on each side point in so that the left lens takes the right side of the picture and the one on the right takes the left side. A single rotating shutter whirling in front of the lenses at the point where their lines of view cross makes simultaneous exposures on each film. Focus and diaphragm controls adjust settings on all lenses simultaneously.

To merge the three films into a single picture on the big 51 by 26-foot screen, three standard projectors in balcony booths throw the images from each film onto the screen. The projector on the right fills in the left third of the screen, the one on the left fills in the right third and the one in the center shoots straight ahead.

Because the screen is curved, there should be distortion and fuzziness, but there isn't. Great depth of focus of the projector lenses keeps the picture sharp. Distortion caused by reflected light bouncing off a screen to the eyes of the viewer has been licked by a Waller trick. The screen is not one great sheet but is made up of 1100 vertical strips of perforated tape, set at angles like a Venetian blind turned sideways. Reflected light bounces off a louver and goes behind the screen. You can sit right at the edge of the Cinerama screen, look up at a tight angle, and figures still look round and full just as they would if you saw them from a seat farther back.

Running three movie reels side by side simultaneously to make one picture poses some problems. If one projector is a fraction of a frame off kilter, the pictures look wiggly. And how to hide the lines where the films come together? This is solved by what the boys call "jiggilos." These are comb-like bits of steel that fit in each projector at the side of the film track and jiggle up and down along the edges of the film at high speed. Like a photographer working a dodging mask under his enlarger to blend clouds




from one negative into a scene from another negative, these saw-toothed dodgers fade the edges of the three Cinerama films where they join and blend them together so there's no sign of a joint.

Keeping those three films synchronized is something else. It's done by a servo mechanism hooked up to a control panel at which the control engineer sits. In front of him are three disks, one for each camera, marked with a pointer and the projector designation, "A," "B" and "C." If all three are in sync, the disks rotate and the pointers on their rims all pass marker points simultaneously. If one pointer lags or gains, the engineer knows he's got an off-kilter picture and adjusts the proper projector by remote control.

The big job comes at the start of the show in getting all the projectors to start together. It's done by the engineer and projectionists talking signals back and forth in the theater over an intercom.

The stereophonic sound that heightens the realistic illusion of Cinerama is as unusual as the movies. When the shooting crew is in the field, five microphones are placed to cover all the action that the camera sees. A sixth is placed well to one side or behind the camera to pick up the sound of people's voices or roaring engines that may be approaching or leaving the scene. Each mike makes an individual magnetic recording on a six-track sound tape. In the theater, five speakers-one for each of the five mikes that cover the action-are arranged behind the screen. Each speaker reproduces the sounds picked up by the mike that was in a similar position on the set. Three other speakers, one on each side wall and another in the rear of the theater, reproduce the off-stage noises that the sixth mike picked up. As a motor boat, for instance, roars across the set, the noise of its engine will be picked up by each of the mikes successively. And that's the way the sound comes out in the theater-moving sound that travels across the screen and roars away behind you.

Critics of Cinerama have decried the bulk and awkwardness of the big camera and the fact that it takes 4 1/2 times as much film to turn out a picture. Each frame is half again the height produced by a standard 35-millimeter lens and the film runs at 26 frames a second instead of 24 (to eliminate flicker which would be noticed out of the corner of the eye). Harry Squire, Cinerama's director of photography, Jack Priestly, technician, and Marty Philbin, electrician, laugh at such talk.




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