Movie Projector

A light source within the projector illuminates images contained on the film as it passes by. The film pauses before the light for a fraction of a second, then advances to display the next frame. It spools into the projector from a device called the feed platter and returns to the platter after it moves through the projector.

Movie Screen

A screen’s material and shape affects how a film will be seen and even heard. Most screens are made of a heavy white vinyl; some have a reflective coating. Small perforations in the material emit sound from speakers located behind the screen. Although screens are often thought to be flat, many are actually curved to prevent a pincushion effect which could distort the image.

Movie Sound

In the most common sound-on-film technology, a transparent line containing audio data is recorded on the film. Light passing through the film is noted by a photocell, which converts the light into an electrical current. The amount of light that shines on the photocell determines the strength of the current.

Source: www.howstuffworks.com

Researched by CHRISTINE FREY/Los Angeles Times