Film projectors trick the eye into believing it is seeing movement.
As you watch the latest blockbuster hit in the movie theater, the only thing you're thinking about is being entertained and the fortune you spent on popcorn, Milk Duds, soda and the price of admission. Have you ever thought about how a famous director is able to show you the vision in his head?
History
The modern film projector was born out of Edison Laboratories (owned by famous inventor Thomas Edison) in 1892, and first demonstrated for the public in 1893 at the Brooklyn Institution of Arts and Sciences. Library of Congress archives state that Edison gave the job to William Kennedy Laurie Dickson to create a moving picture device. The archive says, "Edison called the invention a 'Kinetoscope,' using the Greek words 'kineto' meaning 'movement' and 'scopos' meaning 'to watch.'"
The Mechanics of Film
A film negative operates like carbon-copy paper. Film records images when it's exposed to light. Whatever image is on the opposite side of the light shining through it will be permanently etched onto the negative. American Museum of the Moving Image, "The lens gathers light from the scene that is being recorded and directs it into the film." Lenses are used like magnifying glasses to capture a larger image than the film would capture on it's own.
Playback
Film projectors expose negatives to light a second time so that recorded image can be viewed. Media Services Technical Specialist, Michael Nolte, says, "all movie projectors have several basic elements: a supply arm on which the film to be shown is placed; sprocket wheels that grasp the film's sprocket holes and pull the film through the projector; a film gate." As the film rolls through past the film gate, the shutter opens and closes and allows light to shine through every time a new image passes through it. The individual images captured on the negatives are magnified so that they will be seen on an outside surface.
Effects
At the speed at which these magnified still images pass through the projector, the human eye thinks it's seeing actual motion. The human eye captures images in a similar way as a camera. Light reflects off an object and into the retina, Marilyn Haddrill defines the retina as "the tissue that lines the inside of the back of the eye, where light-sensitive cells (photoreceptors) capture images." To simulate this continuous flow of light and images, film projectors have to pull more than 18 images per second through the viewfinder.
Audio
Digital sounds are recorded on multiple channels onto film in data blocks in a series of numbers between the holes in the film. During playback, digital sound is decoded and broadcast to the audience through a special optical reader that can be mounted onto the projector. Audiences here the audio as closely to the original recordings as technology has allowed thus far.
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