intermittent mechanisms

[Mat Fleming]

Hello, I am a projectionist and a filmmaker and i was wondering if anyone can answer a question I've been pondering. Why do projectors have maltese cross intermittent mechanisms while cameras tend to have claws?

Is it purely a question of size and weight or is there something else?

I'm interested because I've always wondered, but also because I'm looking at constructing a camera for a project I'm doing, possibly out of parts of an old projector mechanism. Does anyone know of any resources out there which might help me?

 

Cheers

 

Mat Fleming.

[Robert Costello]

It might have been a patent issue-

 

from wiki:

The first uses of the Geneva drive in film projectors go back to 1896 to the projectors of Oskar Messter and Max Gliewe and the Teatrograph of Robert William Paul. Previous projectors, including Thomas Armat's projector, marketed by Edison as the Vitascope, had used a "beater mechanism", invented by Georges Demenÿ in 1893, to achieve intermittent film transport.

 

I think if you research any of these names you will get closer to your answer-

 

Maybe the design was a more reliable one, when there were so many that were not-

http://www.victorian-cinema.net/

is a great place to start-

 

it has a great bibliography-

and a lot of the technical information and drawings for

the early cameras is still available-

[Robert Costello]

"An important part of the design was that the cross/sprocket (and therefore film) were locked in between movements, ensuring a steady projection of each static frame. "

 

 

http://www.victorian-cinema.net/features.htm

[Robert Costello]

from :

 

Practical Cinematography and Its Applications (1913)

by Frederick A. Talbot

 

 

"The mechanism of the modern cinematograph

camera is very simple in its character and very

easy to understand. The necessary parts are

very few in number. In all cameras the chief

object is to effect the forward intermittent movement

of the film at regular intervals and for a

defined distance. For this purpose the early

types of camera were fitted with what is known

as the Geneva stop movement. Opinion is

divided upon its merits, some authorities condemning

it unequivocably, while others uphold

it strenuously, contending that it gives a steadier

and freer motion. There is much to be said in

favour of the latter view. Mechanically the

Geneva stop movement is perfect. So far as

cinematography is concerned its advantages were

proved most emphatically by Mr. Robert Paul,

the first man to bring motion pictures into commercial

application in Great Britain. He adopted

this movement in his camera, and it cannot be

denied that his pictures were in every way equal

to those produced to-day, while his camera has

never been excelled. Curiously enough, although

this movement has been superseded, there is a

tendency among expert workers to revive it,

and many cameras specially built have been fitted

with it.

The movement more commonly used is that

known as the "claw." It is simple, and has the

advantage of bringing the film into place for an

exposure with a sharp, quick jerk. But it is a movement

which requires to be designed very finely

in order to perform its work smoothly and evenly,

and without inflicting any injury upon the film."

[Dom Jaeger]

I would imagine that a claw movement, with its eliptical travel designed to enter, pull down and exit the film perf at more or less the same angle, would be less damaging to the perf than a geneva movement, which would enter at one angle, swivel as it pulls down, and exit at a different angle.

[John Sprung]

The Geneva movement is a mechanism that drives a sprocket intermittently. It's extremely noisy compared with the various claw pulldown designs. It's used on projectors and on the old upright Moviola editing machines. Because it drives a sprocket with several teeth engaged on both sides of the film, it's relatively gentle on the film. But the Geneva pulls down rapidly, in 90 degrees or less. Cameras usually use shutters of 180 degrees or thereabouts, and they don't need to pull the film that quickly. The slower claw pulldown makes less noise.

 

 

 

-- J.S.

[Mat Fleming]

Hello,

 

Thanks for all your responses and the links to interesting reads. I've been away a few days so I have only read them all just now. I love the elegance of the Geneva movement/Maltese cross but it's true they can be really noisy.

 

thanks again

 

Mat

[Robert Costello]

Would camera noise be an issue in the silent days?

Unless the aim was to film more naturally with less noise distractions in

say slice of life or travelogue films- but I can't see that as being a concern in the

early days-

 

It would seem that the quiter mechanism would be a greater advantage during exhibition, where

music and narration was common-

 

and all this is assuming that by at least 1913 the Geneva cross was only in special built cameras-

[John Sprung]

For exhibition, Geneva pulldown projectors are used in well insulated booths to control the noise. For portable in-the-room projectors, mostly 16mm, they go with a claw pulldown.

 

As for early cameras, a simple bell crank and guide slot pulldown is a bunch easier and cheaper to make than a Geneva. Noise wouldn't be the deciding factor.

 

 

 

 

-- J.S.