Projectors
The projectors often are: 16 mm film movie projector, a 35 mm slide projector and a 35 mm film movie projector. In low-end use the motion picture 35 mm projector would be replaced by a second 16 mm projector or 8 mm film, or Super 8 mm film or Single-8 projector. The multiplexer with the camera and projectors surrounding it would often be called a film island. The optical or mag or magnetic strip sound track on the motion picture would be picked up by the projector and would be fed to an audio sound mixing console or to the VTR. See: Sound-on-film, Film Sound and 35 mm Sound.
The slide projector at a TV station would be used for the TV station’s logo, the famous “Please Stand By” slide and some test patterns. Some used a dual-rotating drum slide projector that would have its own mirrors to switch between the drums.
The film projectors used in a film chain are not standard. A special five-blade shutter is used to convert the film’s 24 frames per second into NTSC’s 30 frame per second video. If this was not used, the video would have major flicker problems. This process is called a "3:2" pull down. Modern telecines use the same process, but it is done electronically, not with a five-blade shutter. "3:2" pull down means that a film frame is shown for three TV fields. The next film frame is shown for 2 TV fields. The add field in the “3” is used to convert the 24 frames per second to 30 frames per second. A normal projector has a 2 bladed shutter that shows the same frame twice. Before modern continuous motion telecines, film chains were sometime referred to as telecines.
All film projectors use sprocket rollers to move the film and a pull-down claws to move and stop the film in the gate. The film is moved in the gate while the shutter blocks the light.
In PAL, SECAM and other 25 frames per second systems, the film projector speed is increased one frame per second to 25 frame/s. This gives a one-to-one film to video frame transfer ratio. Thus a standard 2 bladed shutter can be used.
See frame rate differences for more information.
Read more about this topic: Film Chain