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• To record the history of the large format movies and the 70mm cinemas as remembered by the people who worked with the films. Both during making and during running the films in projection rooms and as the audience, looking at the curved screen., a unique internet based magazine, with articles about 70mm cinemas, 70mm people, 70mm films, 70mm sound, 70mm film credits, 70mm history and 70mm technology. Readers and fans of 70mm are always welcome to contribute.

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Todd-AO How It All Began #4

The 70mm Newsletter
Written by: Brian O'Brien, Jr. American Optical Company. Brian O'Brien, Jr. was employed at American Optical Company during the development of the Todd-AO process 1953 - 1957. He was generally in charge of planning and development of picture production equipment. Issue 50 - September 1997

Film and Sound

Now back to the film, and sound. We wanted to have nearly as possible true stereophonic sound. Now a slight digression for definitions. There are two methods of giving the observer the sensation of directionality in his perception of a sound - Stereophonic and Binaural reproduction. The simplest is binaural where each of the observers ears is presented with exactly what the ear would receive (in both amplitude and phase) if he were sitting at the original location (such as in a concert hall). This is done in practice by recording with two microphones placed like ears, and then reproducing this into earphones that must be worn by the listener. On the other hand, with stereophonic reproduction you do your best to reproduce the complete sound field in the theater that existed at the original location. This is normally done by multiple soundtracks and multiple speakers behind the screen and around the theater. For perfect reproduction an infinite number of both would be needed, but as a practical matter six sound tracks with three speakers behind the screen and three sets of surround speakers does an adequate job. In addition, there is a trick to enhance the sound localization effect. For a person sitting in the rear of the theater a sound coming from, say, the left screen speaker will not appear to be very far off center because of the small angle to the left. However, if that same sound then comes from the left surround speakers delayed in phase by a fraction of a second, the impression will be of that sound increased in amplitude and from way to the left.

Because of this we wanted six soundtracks, three for the screen speakers and three for the three sets of surround speakers. The problem was that there was not room on the 65mm film. The solution was to go to 70mm film. However, it was extremely desirable to be able to run the camera film and print film on the same sprockets, so the extra 5mm was added outside the perforations and the soundtracks were placed out there.

Magnetic sound recording had surpassed optical sound in quality, and the best was using the Minnesota Mining and Manufacturing Company’s (3M Co) so-called green oxide, which had the ferrite crystal all oriented so the noise level was much better than with the liquid applied striping on motion picture film. We initially went that route but there was one big problem. 3M (of all people!) had trouble with the adhesive used to laminate it to the film. The sound track would peel off on the projection room floor. Hence we ended up with liquid striping for our prints with two sound tracks outside the perforations and a third track was inside the perforations on each side.

In those days, (and I presume still today) multitrack sound was recorded on 35mm magnetic film with standard 35mm perforations and this was run at standard motion picture speed of 96 perforations per second (24 four perforations frames per second). We used a 5 hole pull down at 30 frames per second, and so our film moved at 150 perforations per second. Of course, this is the same ratio as 64 perforations (one foot) to 100 perforations (which we named the “gleep”). Since standard sound recording equipment was to be used, the editing “sync machines” had to be built with 65/70mm picture sprocket with a larger diameter than the sound film sprockets in the ratio of 100/64. We built a series of sync machines with one picture sprocket and from one to six sound film sprockets on the same shaft.
More in 70mm reading:

You are in the Show with Todd-AO

Todd-AO How It All Began #1
Todd-AO How It All Began #2
Todd-AO How It All Began #3

Todd-AO Birth Date

Hollywood Comes to American Optical Co.

Walter Siegmund Interview

DP70 - The Todd-AO Projector

Internet link:


Editing Machines

Remember that this was the era when most editing was done on the old Moviola machines. The Westrex division of the Western Electric Co. had just recently introduced their new editor that used rotating prisms (glass cube) and continuously moving film instead of the intermittent sprocket pulldown of the Moviola.

The Westrex machine was far superior, so we had them build them for our film. They couldn't handle the optics, so we provided the eight sided rotating prisms. In addition to a magnificent direct view of the film, we designed them so that the editor could project the image onto a curved screen so as to be able to better visualize the effect in a theater.

Another modification was to have the sound film run at a different speed than the picture film i.e., one foot of sound film to one gleep of picture film so that they would stay in synchronism (the 64/100 ratio).

Editing Accessories

All of the editing accessories, such as reels, hand rewinds, tight winds, of course had to be made to accommodate both 65mm and 70mm film. The editing reels had to be made for either 65 or 70, but the rewinds didn’t care and the weighted roller on the tight winds for spooling film tightly onto core were machined with a smaller diameter, 65mm wide, portion inside the 70mm lands and flanges.

Splicers had to be made for the film. We had Bell & Howell build a treadle splicer for us and we built a few hand splicers.


I have described the image characteristics of the wide angle or “Bugeye” lens earlier. The field of view was 132 degrees wide with the frame capturing 128 degrees. Because of the distortions described before, the lenses did not have a single focal length, but rather the focal length varied depending on the position in the field. Thus we designated the lenses by their angular coverage rather than the focal length designation of standard cine lenses.

Mike Todd in Spain filming "Around the World in 80 Days"

Initially we intended to have only the “Bug Eye” lens, analogous to Cinerama's equivalent of only one “lens”. However, the Hollywood types insisted that they must have a series of “longer focus” lenses for close-ups etc. We tried to explain to them that they would lose the audience participation effect if they went to narrower angles, but they insisted that they would only use them for close-ups. As a result we gave them 64, 48 and 32 degree lenses in addition to the 128 degree Bugeye. It was the biggest mistake we ever made!! These great “professional” cinematographers and directors didn’t have the faintest idea how to use the wide angle or participation effect, and so in the whole of “Oklahoma!” the Bugeye lens was used for two shots, the opening scene dollying through the corn, and one cut from the runaway buckboard carrying Laurie and Jud to the Claremore party. The rest was all shot with the narrow angle lenses. Mike [Todd] used the wide angle a bit more in “Around the World in 80 Days” but not a great deal more.

The Corn in “Oklahoma!”

65mm frames from "Oklahoma!" program.

Some interesting sidelights on the corn in “Oklahoma!”. In the San Rafael valley south of Tucson, near the Mexican border where they built Aunt Eller's house, it was too cold and dry to grow corn very well. They hired a plant pathologist from the University of Arizona to try and do it. By starting it early and watering it daily from a tank truck driven up from Nogales, he was able to get a small corn field grown near the house. It was so short, that for shots of Father Carnes coming through the corn field, James Whitmore had to squat down to make the corn look tall enough! We estimated that the corn cost about $8.95 per ear. For the 19 second opening shot through the corn to a panoramic shot they had to inject each stalk of tall corn (corn never had been transplanted before), put it in a pot, and truck it up to the top of the hill to make a corn field just for that shot. The shots of Curly riding past corn singing “Oh What A Beautiful Morning” were all taken in the valley down near Tucson at some farmers stand of tall Mexican June corn. Finally they got corn “as high as an elephant’s eye”.
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Updated 17-12-17