This is normally 24 seconds per still image shown. Because 24 light-dark cycles of the human eye would be perceived as annoying flicker, each frame in the prior addition of the rotary shutter interrupted, which are generated for the change of eye 48, so that each film frame is shown twice. There are also projectors with 18 (in Super-8 movies) or 25 frames per second (for television). Most silent films should be presented with 16 to 22 frames / sec. For scientific purposes projectors exist in a wide range of variable frame rates . Even municipal cinemas are usually equipped with projectors with variable speed. Because of the German-speaking normal mains frequency of 50 Hz television uses 50 frames per second, with a frame frequency of 25 Hz to avoid interference films are therefore on TV instead of 24 Hz broadcast at 25 Hz, thus the term to 4% shorter. A film of 100 minutes (movie) Time is on TV or on video that is only 96 minutes. After a century of film projectors were long without competition, since 2000, cinemas are increasingly on digital film projection to.
Components
The key elements of a film projector are the film drive (for example, a Maltese-cross-locking in conjunction with switching role or a hook), which transports the film in the dark period for him in the light phase as long as possible project can resting. The film runs in a so-called film gate, where he will be along, across and out along the optical axis (see the nomenclature of the narrower film technique ). The rotary shutter (sector disc), which interrupts the light beam, while the film is transported, and then one more time in the middle of the moment in which the film image is shown (increasing the flicker frequency)
Spent carbon of carbon arc lamp of a film projector
Above: 4000 watt xenon lamp is defective, Bottom: 2000 watt xenon lamp, unused in protective housing Film projector with carbon arc lamp 16-mm film, blown film in which an image is due to blocking of the film transport, because the film door was not closed in time Path of a 16-mm film projector with picture window Projectionist when cleaning the film path of a projector Askania AP XII (clearly visible above the fire drum, including the tape recorders) the light source: with 35-mm film , as it is usually played in cinemas, this used to be carbon arc lamps , today there are xenon arc lamps , usually with between 900 watts and 10 kW of electric power (the most common xenon lamps have 7000 W). For 16-mm films are partially xenon lamps, halogen partially bulbs used. 8-mm film projectors usually have halogen bulbs. First 35-mm film projectors for home use and normal bulbs or kerosene lamps.
a condenser of the light source on the aperture plane of the lens projected the image masks (picture windows) for the different image or Projection formats to track and perforation are also not visible on the screen. =================== Projection lens Diastar one Askania 35mm film projector with a 400 mm focal length the light valve, a metal screen between the film and the lamp, which closes automatically when the film cracks or projector stop and turn the film in front of the lamp heat protection (jammed the door, burn the movie), and is otherwise served by the demonstrators, in order not to demonstration imaginary parts of the film as the band start to hide the projection lens to project the image is sharp and in the correct size on the screen the sound device for optical sound or magnetic sound , the soundtrack of the film samples ========== Movie Drive
When you replace the current development mechanisms through a step motor in conjunction with switching role. Benefits are supposedly improved picture stability , improved light utilization through shorter response times (the time needed to advance the film one step) and lower film and equipment replacement. Furthermore, there are processes in which the film is not sold, but moves continuously being. The light of the image passes through a system of synchronously rotating prisms to the film movement in the lens or mirror. The company Ernst Leitz built the operating by this principle Mechau projector . The procedure is also used for small, on a ground glass viewing imaging devices.
Wide-screen process
Movies in wide screen can be masked, ie when the projection is only an excerpt of the maximum possible image format shown. Are consistently the American widescreen with an aspect ratio of 1:1.85 and the European widescreen with an aspect ratio of 1:1.66. To distinguish them is the Cinemascope process, in the film distorts the image into the recording: it can be included in the width more information, the image is in the horizontal plane by a cylindrical lens compresses. For showing such films, the projector with an anamorphic lens to be equipped with the image is rectified. The aspect ratio of the projected image is equalized at Lichttonkopien 1:2.35.
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