Many of the earliest films shot in the USA were made in the east where good sunny weather was not reliable. Movies were made indoors, in buildings with as much glass as possible on the outside walls and roof. Movie-making’s most valuable commodity was light.
Since noise was not an issue in silent filmmaking, it sometimes happened that more than one film was “on the floor” at the same time, each making its own din.
Outdoor scenes were often faked indoors. The simplest device was a painted backdrop, like the ones seen in theatres. A later generation of backdrops was painted on a continuous loop of scenery canvas, and moved horizontally by pulleys, to show a countryside that appeared to be passing by. A train interior could be filmed in a cutaway set in front of such a moving diorama to create the appearance of the moving train; a cowboy on a model of a horse, being rocked by off-screen “grips” was riding the range.
A later, more sophisticated system substituted a movie screen for the canvas, and actual outdoor scenes were shown on the movie screen. The action taking place in front of the screen was made to look “on location”. Because the image was projected from behind the screen, this process was called “back-screen-projection”.
Alfred Hitchcock, a director who liked to control every possible detail in his films, disliked the uncertainty of outdoor shooting, and went to great lengths to shoot as much action as possible in the studio. He was a tremendous fan of back-screen-projection.
A much more complex system that could bring the outdoors indoors was the matte shot. It is essentially an elaborate kind of double exposure. Imagine a room with a large window through which the script calls for a train to be seen arriving at a station. Here’s how such a shot could be done using a matte system.
First the window is covered with thick black cloth. The action inside the room is then filmed, with a part of the lens covered that exactly corresponds with the part of the frame where the window would be photographed. Without opening the camera, the film is then rewound to the exact beginning of the shot just taken, and another cover for the lens is attached blanking out the entire frame except the part that had previously been covered. The camera is then taken to a railway yard to film a train, and the image of the train appears only in that part of the frame left unexposed in the first shot – i.e. the window.
When the film is processed, the two images are on the same strip of film and the train appears to be arriving outside the window.
Chris Worsnop