Filmstrip

he two basic elements of cinema are the movie camera, which lets in light, imprinting images on film, and the film projector, which uses light to project the film onto a screen. At its essence, projected film is a series of single images shown in rapid succession. A neurological phenomenon called “persistence of vision,” wherein the eye and brain retain an image for a brief period of time, makes the projection seem like natural motion and not a series of single photographs. The industry standard for movie projectors is 24 frames a second, which came about around the time of the first films with sound in the late 1920s. In the projector, the assembly that keeps the film moving begins with those ubiquitous holes on the edges of film stock, called sprocket holes which link up to the teeth of the sprocket, an electrically powered wheel that feeds the film into the camera from the feed platter, basically a giant spool. In this process, the film is kept taut by rollers called cambers. This leads to the aperture, and the film is held tight to the film gate, which lets the light source for the projection shine through the film, then the lens, and out onto the cinema’s screen. Nowadays, xenon arc lamps are the standard light source, but arc lamps grow so hot that if the film would melt if it stopped moving. Even so, a fraction of a second pause is required as the film passes in front of the lens assembly, and this pause is accomplished either by the movement of a lever or sprocket wheel. The final element in creating the projection is the shutter, which (very quickly) blocks the light during the transition between frames. If this light blockage didn’t happen, blurred images are all that would be visible. Then, the film, having finished its job, goes into the take-up platter. Somewhere in this process—it varies from system to system— the sound information on the film is read. Words: Michael Isenbek I Photo: Stephen Lang

michael isenbek

Michael Isenbek, Associate Editor, dabbles in both fiction and nonfiction writing, coordinates the Pulse event listings and writes the text for "Zoom," among other editorial tasks. He has a Master's Degree in Liberal Studies and a Bachelor's Degree in Cultural Studies with a concentration in Journalism from SUNY Empire State College.