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Todd-AO Projection and Sound
Questions and answers about the workings of the newest system for new
dimensions in the art of motion picture presentation
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Read more at
in70mm.com
The 70mm Newsletter
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Written by: Showmen’s Trade Review, October 15, 1955 |
Date: 01.07.2008 |
Question: What is the Todd-AO system?
Answer: Todd-AO is the ultimate result of intensive research by a team
of research and engineering scientists headed by Dr. Brian O'Brien at
the American Optical Company laboratories and of the Cinema Department
of the Philips Works, Eindhoven, Netherlands. It is a motion picture
process which employs one camera and one projector. The final results
are said to take the motion picture technique a step closer to smashing
the illusion barrier between the real and the make-believe.
Question: How was the Todd-AO system originally conceived?
Answer: Michael Todd went to Dr. Brian O'Brien at Rochester, New York,
to ask if such a system could be created. O'Brien, said to be the
Einstein of optics, answered that it was possible but that the
facilities of a large optical firm would be required. Todd then
approached the American Optical Company to undertake this and was
informed at that time that O'Brien had agreed to join it.
Question: Is the Todd-AO projector adaptable to other media?
Answer: With the exception of Cinerama, the projector has switch-Iever
adaptability to all media. Changeover of the Todd-AO projector to any
other system is said to be "almost immediate."
Question: What is new in filming a picture in Todd-AO ?
Answer: The cameras are new although similar in general principle of
operation to standard 35mm cameras. The lenses used in the photography
are completely new. The sound recording system is unusual in that it
provides six independent sound channels with high fidelity and
signal-to-noise ratio.
Question: Why is 65mm film used?
Answer: 65mm film is used in the cameras to provide a picture area
nearly four times that of the standard 35mm camera frame. This larger
picture area is said to permit greater detail and sharpness in the
picture projected in the theatre.
Question: Why is 70mm film used in the projectors?
Answer: The projected picture is the same size as the camera negative
picture, but 70mm film is used in the projectors to provide space on the
film for the six magnetic sound tracks.
Question: Why is the film speed 30 frames per second?
Answer: Thirty frames per second has been selected instead of the usual
24 frames, to reduce flicker and to give greater continuity to rapid
motion across the screen. if the picture is large the eye is more
sensitive to flicker.
Question: How does Todd-AO plan to eliminate image distortion from
Keystoning due to projection on a deeply curved screen from high angles
of projection?
Answer: The American Optical Company method of photographic printing, it
is claimed, not only eliminates Kestoning but other distortions
resulting from projection on a deeply curved screen from high angles in
the theatre.
Question: What is the Todd-AO screen made of?
Answer: The Todd-AO screen is made of long fibre cotton fabric
impregnated and coated on both sides with slow-burning plastic in order
to meet theatre fire prevention requirements. The screen is porous to
permit light to pass through instead of bouncing back into the eyes of
patrons, and is imbedded with pin-point sized mirrors at the ratio of
600 to a square inch. The mirrors direct light and are said to prevent
re-illumination of light from one side of the deeply curved screen to
the other.
Question: What determines screen size and curvature?
Answer: The size of the Todd-AO screen is determined largely by the size
of the theatre into which it is to be placed.
Question: What are the advantages of a deeply curved screen?
Answer: The most important visual result is that a very large portion of
the audience has a sensation of personal participation in the scenes.
Another aspect of the deeply curved screen is its comparative freedom
from squeezed images when viewed from the side seats in the front rows.
The ability of the deeply curved screen to avoid "squeeze" is stolen
straight from Euclid's "Geometry." Euclid taught that for an observer
standing on the edge of a circle, equal arcs subtend equal angles
anywhere on the circle. On the Todd-AO screen this has the result that
an observer can walk right up and lean his cheek against the screen, and
still get a good view of the picture.
Question: As a rule, what size screen is preferred in Todd-AO ?
Answer: As a general rule the preferred screen is the largest screen
that it is possible to build in the front of the theatre.
Question: What are Cine-Apergon projection lenses?
Answer: The Cine-Apergon projection lenses are a series of seven
projection lenses designed for the Todd-AO system. These are lenses of
unusual speed and capable of covering the wide film with crisp realism
to the very edges. Without the use of special aspherical optical
surfaces, the projection lenses would have been the weak point in the
system.
Question: Can Todd-AO projectors be used in upward-throw drive-in
theatres?
Answer: Yes. The projector includes a tilting mechanism which rotates
around a high point so that there is only a slight movement of the
center of gravity. Projection angles of as far down as 28° and as far up
as 20° can be reached.
Question: What are some of the features of the Todd-AO projector?
Answer: The projector will take 70mm film or 35mm film with only minor
adjustments in the mechanism, and can be changed in about four minutes.
The projectors are equipped to handle multi-channel magnetic sound for
Todd-AO, 35mm magnetic sound for CinemaScope, or conventional optical
sound. All three sets of sound equipment are provided and the only
change necessary is to thread the film through the desired sound head.
Sound on separate film can be used with a selsyn synchonizer system that
is available. Only certain high-power arcs are recommended for the
Todd-AO system. An unusual feature of the design is that all the
mechanism, including sound heads, is included in the projector head thus
eliminating the possibility of errors due to unequal reel pressure.
Other features include a centrifugal switch to drop the dowser if the
film speed is too low, a water flow switch to cut off the arc if the
cooling water is cut off, and stop switches on both sides of the
chassis. The optical preamplifier is of a special plug-in design so that
a new unit can be substituted almost instantly in case of breakdown. Two
separate motors are provided to run at 30 and 24 frames per second
respectively.
Question: Is the Todd-AO system completely integrated?
Answer: Yes. Any attempt to compromise on its installation in the
theatre would be as self-defeating as trying to run an automobile with
some of the parts missing.
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More
in 70mm reading:
Todd-AO
The Todd-AO Projector
Showmen’s Trade Review, October 15, 1955:
Oklahoma! in Todd-AO
Todd-AO
Magna Theatres
Todd-AO Corporation
Philips Collaborated On Projector Design
Todd-AO Projection and Sound
Six track recording equipment
All-Purpose Sound Reproduction
Rodgers & Hammerstein II
Six track recording equipment
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28-07-24 |
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