Cinema Canada (Aug 1979)

TEC4 NEWS CAMERA TYPE TELECINES ono. 2 ina series of 10 The following is the second in a Series of articles written by Rodger J. Ross for Cinema Canada about film _ postproduction on videotape. It was’ first printed ~ and badly so in issue no, 54 of the magazine under the title “Vidicon Cameras for Telecine Service.”’ Not only was the title misleading, several of the paragraphs were out of order, rendering the article incoherent. Cinema Canada reprints the article in this issue with our apologies to Mr. Ross for the errors in issue no. 54. The third:-article in the series, ‘“Flying Spot Scanners: Film Post-Production on Videotape,” was printed in issue no, 55; the fourth of the series, “Making Recordings on Videotape” also appears in this issue of Cinema Canada, FILM POST-PRODUCTION ON VIDEOTAPE — Second in a Series Camera-Ty pe Telecines. By far the most popular method for reproducing films and slides in North American television is the multiplexed camera-type telecine chain. Usually, telecine chains consist of two 16mm. projectors and a slide projector optically multiplexed into a television camera. As a rule, the film projectors are mounted at right angles to the right and left of the multiplexer, while the slide projector “looks” directly through the optical system into the camera. Moveable mirrors in the multiplexer can be shifted by remote control from a production coordinating studio, directing the light beam from any one of the projectors into the camera. These Long time Supervisor of Technical Film Operations at the programming centre of the CBC, Mr. Ross is the author of two books, Television Film Engineering and Color Film for Color Television, has won the Agfa-Gevaert Gold Medal awarded by the Society of Motion Picture and Television Engineers, and is presently Chairman of the SMPTE Board of Editors. 32/Cinema Canada by rodger j. ross telecine facilities are designed to give continuous uninterrupted output over long periods of time. In one quite common multiplexer model two mirrors 90 deg. apart are mounted on a vertical shaft and driven by air pistons. With film running in both projectors and the mirrors set to direct the light beam from one of the projectors into the camera, depressing the remote control button for the other projector shifts the mirror assembly in a fraction of a second to its new position. This cuts off the light from the first projector and directs the light beam from the other projector into the camera, producing an effect similar to a straight cut (splice) between two scenes. When a third button is pressed the mirror assembly shifts into a position where both film projector light beams are cut off, and only the light beam from the slide projector can enter the camera. Remote control buttons are provided also to start and stop the film projectors. In some telecine installations projectors can be stopped automatically at the end of a program sequence by a patch of magnetic foil attached to the edge of the film. Slide projectors for telecine service are usually fitted with two drums or carousels to enable slides to be shown in a continuous sequence without dark periods between successive slides. This is accomplished by projecting the first slide in a sequence from one drum, and then, when the “slide change” button is depressed, the next slide in the sequence is projected from the other drum. The change-over from one slide to the next usually appears as a rapid dissolve rather than a straight cut. Vidicon Cameras for Telecine Service. Most telecine chains in broadcasting stations utilize vidicon cameras for generating color video signals from films and slides. A color telecine camera consists in reality of three separate camera units, each fitted with a vidicon tube, to produce separate red, green and blue signal outputs. These units are located on adjustable mountings in a common enclosure containing also the filter and mirror or prism assemblies for color separation. Surrounding each tube are sets of alignment, focus and deflection coils to control the scanning action of the electron beam. The optical system in a telecine chain is quite complex. Two factors complicating the design are the long optical path between the projector gates and the face plates of the vidicon tubes — 30 to 40 ins. or more in some layouts -. and the small size of the useful photo-area in the vidicon tubes. To achieve a magnification ratio of approximately 1:1 for 16mm. film images, a common practise is to utilize a large field lens at the entrance port of the camera. The film and slide A LOT CAN HAPPEN BEFORE YOU GET IT IN THE CAN Play it smart and protect yourself in the professional manner with insurance Let's discuss it Arthur Winkler, CLU Consolidated Insurance Agencies Ltd. 3101 Bathurst St., Suite 201, Toronto, Ontario M6A 2Y1 Telephone (416) 787-0304