Film chain

A film chain or film island is a television – professional video camera with one or more projectors aligned into the photographic lens of the camera. With two or more projectors a system of front-surface mirrors that can pop-up are used in a multiplexer. These mirrors switch different projectors into the camera lens. The camera could be fed live to air for broadcasting through a vision mixer or recorded to a VTR for post-production or later broadcast. In most TV use this has been replaced by a telecine. 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 soundtrack 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 familiar "Please Stand By" slide, Emergency Broadcast System test or alert slides 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 two 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 two-bladed shutter that shows the same frame twice.