Film - A Practical Guide to Video and Audio Compression - page 44

tried and discarded before the sprocket-driven serial frame design became dominant.
A visit to the National Museum of Film and Television in Bradford, UK or the Science
Museum in London will reward you with some insights into the way that film technology
has evolved. Both of these are worth visiting if you have the time. There are similar muse-
ums in the United States (such as the California Museum of Photography) and in other
countries where there is any history of filmmaking. Some URLs for Web sites of other
museums are listed at the bottom of the page. Museums featuring scientific or engineer-
ing subjects may also have sections devoted to filmmaking.

4.3.1 Gate and Film Transport Mechanism

The film is pulled through the gate of the camera and projector by a claw mechanism that
is driven by a cam or eccentric motion of some kind. This is easier to understand if it is
shown visually. Figure 4-1 demonstrates how this mechanism works.
As the motor drives the eccentric cam around, the claw is moved up and down and
in and out. This is a vastly simplified example and the actual mechanism is a bit more
complicated than this, but the principle is the same. The claw moves up, the teeth come
out through an aperture in the gate, and they penetrate the film via the sprocket holes and

Eccentric
motion

Claw motion

Figure 4-1 Film gate claw mechanism.

National Museum of Film & Photography: http://www.nmpft.org.uk/
George Eastman House: http://www.eastmanhouse.org/
American Widescreen Museum: http://www.widescreenmuseum.com/
California Museum of Photography: http://www.cmp.ucr.edu/
American Museum of Photography: http://www.photographymuseum.com/guide.html
International Centre of Photography: http://www.icp.org/
The Big Camera: http://www.thebigcamera.com.au/