How does it work? – Cinema projector

How does it work? – Cinema projector

This animation demonstrates the design and operation of a traditional cinema projector.

Technology

Keywords

film projector, cinema, movie, motion picture, film, film screening, projection box, film reel, optics, frame, film drive mechanism, digital, analogue, stereo soundtrack, media, technology

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Scenes

Projection booth

  • analog projector

  • - A cinema projector projects 24 frames per second. These 24 images take up half a meter (1.64 ft) of film. The length of the film strip of a 2-hour film is approximately 3.5 km (2.175 mi). Previously such long film strips were wound on multiple film reels. To ensure continuity during the projection, a pair of film projectors were alternately used. Today, the use of large film reels is no longer a problem, thus one projector is enough to use.

  • - An analog cinema projector projects 24 frames per second, which are not perceived by our brain as individual images. The series of still images displayed in quick succession blend in with each other. This is the basic principle of film technology.
  • - The audio signals can be recorded and reproduced on the sound track optically or magnetically. Modern films contain digital sound tracks rather than analog ones.

Narration

The cinema projector projects 24 frames per second, which are, however, no longer perceived by our brain as individual images. These still images simply blend together. This is the basic principle of film technology. If the movement of the film and the illumination were continuous, the image on the screen would be blurry. Therefore the film is moved frame by frame and the lamp does not illuminate the frames while they are in motion. As the motion of the individual frames cannot be seen, the image on the screen is not blurry.

A cinema projector projects 24 frames per second. These 24 images take up half a meter (1.64 ft) of film. The length of the film strip of a 2-hour film is approximately 3.5 km (2.175 mi). Previously such long film strips were wound on multiple film reels. To ensure continuity during the projection, a pair of film projectors were alternately used. Today, the use of large film reels is no longer a problem, thus one projector is enough.

Perforations on the edges of the film strip are used for moving the film along. The audio signals can be recorded and reproduced on the sound track optically or magnetically. Modern films contain digital sound tracks rather than analog ones.

One of the disadvantages of analog cinema projectors is that the film is vulnerable. Reproducing the film is also more complicated than it is in the case of digital technology.
Digital, LCD projectors are becoming more and more widespread. Besides the many advantages, they also have disadvantages. Their operating costs are relatively high and one pixel error in the projector can be seen during the entire length of the film. Therefore, most cinemas still use analog projectors.

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