TEO-l nEWf by Rodger J. Ross VIDICON CAMERAS FOR TELECINE SERVICE Most telecine chains in broadcasting deflection linearity pattern. This pattern telecine service are usually fitted with stations utilize vidicon cameras for gen­ is utilized together with an electronical­ two drums or carousels to enable slides erating color video signals from films ly generated grating to obtain exactly to be shown in a continuous sequence and slides. A color telecine camera con­ matching images from the three vidicon without dark periods between succes­ sists in reality of three separate camera tubes. sive slides. This is accomplished by pro­ units, each fitted with a vidicon tube, to jecting the first slide in a sequence from produce separate red, green and blue 2. Camera-Type Telecines one drum, and then, when the "slide signal outputs. These units are located By far the most popular method for change" button is depressed, the next on adjustable mountings in a common reproducing films and slides in North slide in the sequence is projected from enclosure containing also the filter and American television is the multiplexed the other drum. The change-over from mirror or prism assemblies for color camera-type telecine chain. Usually, tel­ one slide to the nex t usually appears as separation. Surrounding each tube are ecine chains consist of two 16 mm. a rapid dissolve rather than a straight sets of alignment, focus and deflection projects and a slide projector optically cut. coils to control the scanning action of multiplexed to a television camera. As a An alignment and resolution test the electron beam. rule, the film projectors are mounted at pattern is also available from SMPTE, The optical system in a telecine chain right angles to the righ t and left of the consisting of a target defining the por­ is quite complex. Two factors compli­ multiplexer, while th e slide projector tion of the projected image fram e to cating the design are the long optical "looks" directly through the optical be reproduced in the television system, path between the projector gates and system into the camera. Moveable mir­ and useful also for accurate alignment face plates of the vidicon tubes ~ 30 to rors in the multiplexer can be shifted by of the telecine projectors with the 40 ins. or more in some layouts ~ and remote control from a production co­ camera, as well as for adjusting optical the small size of the useful photo-area ordinating studio, directing the light and electronic focus. The " barber in the vidicon tubes. To achieve a mag­ beam from anyone of the projectors pole" border around this pattern en­ nification ratio of approximately l:l for in to the camera. These telecine facili­ ables adjustments to be made in the 16mm. film images, a common practise ties are designed to give continuous un­ scanned area, and groups of vertical is to utilize a large field lens at the en­ interrupted output over long periods of and horizontal lines in converging pat­ trance port of the camera. The film and time. terns provide a critical test for focus. slide projectors produce aerial images at In one quite common multiplexer the plane of the field lens, and these model two mirrors 90 degrees apart images are then focused sharply at the are mounted on a vertical shaft and Picture Gray Scale and Color face plates of the vidicon tubes. The driven by air pistons. With film run­ Reproduction light beam en tering the camera from a ning in both projectors and the mirrors The color television system as we projector is split in to red, green and set to direct the light beam from one of know it today in North America was blue components by dichroic filters, the projectors in to the camera, depress­ developed in the USA in 1953 by the and these three colored beams are then ing the remote control button for the National Television Systems Commit­ reflected off front-surfaced mirrors to other projector shifts the mirror assem­ tee , from which the designation the corresponding vidicon tu bes. bly in a fraction of a second to its new "NTSC" derives. A basic consideration p.osition. This cuts off the light from the in this system is what might be termed first projector and directs the light beoam "neutral balance." This means that a Color Registration from the other projector into the cam­ properly aligned telecine chain should The scanning patterns produced in era, producing an effect similar to a give a neutral (colorless) picture from the vidicon tu bes must be exactly the straight cut (splice) between two scenes. a gray scale, as well as from black-and­ same size and shape, and must be exact­ When a third button is pressed the mir­ white films or slides. ly registered at the camera output to ror assem bly shifts in to a position where give television pictures free from color­ both film projector light beams are cut fringes. This is an additive system in off, and only the light beam from the Long time Supervisor or Technical Film which red , green and blue images are slide projector can enter the camera. Operations at the programming cen tre superimposed to produce all the other Remote control buttons are provided of the CSc. Mr. R oss who is th e author colors of which the system is capable. also to start and stop the film projec­ of two books. Television Film Engineer· The Society of Motion Picture and Tel­ tors. In some telecine installations pro­ ing and Color Film for Color Television, has won the Agfa-Gevaert Gold Medal. jectors can be stopped automatically at evision Engineers makes available several awarded by the Society of Motion Pic­ test patterns in 35 and 16mm. film and the end of a program sequence by a ture and Television Engineers. and is 2x2" slide formats for the alignment of patch of magnetic foil attached to the presently Chairman of the SMPTE telecine equipment. Among these is a edge of the film. Slide projectors for Board of Fditors. 44jCinema Canada TEO-l nEWf Eastman Kodak Co. produces a are laid down on the glass surface in ever, in the alignment of the equipment gray scale telecine test slide 3 1/4x4 triads, there is a perforated metal to make sure that pictures with the best ins. in size designed to be inserted at screen that allows only one of the possible quality are being obtained. the field lens position. During align­ electron beams to strike the corres­ SMPTE supplies subjective color refer­ ment of the camera , the slide is illumi­ ponding dots. Thus, the "red" elec­ ence films or slides that can be projec­ nated by running one of the projectors tron beam, representing the red por­ ted in a review room, and then repro­ with open ga te. At the camera control tions of the film images, strikes only duced in the telecine for comparison. console, it should be possible to dis­ the red phosphor dots, and the green play the outputs of the three camera and blue dots are excited in a similar tubes side-by-side on a waveform mon­ manner. As the signals applied to the itor. Depending on the color of the electron guns vary, the brightness of projector light source, the settings of the colored dots increases and de­ the camera controls at the time and creases, producing the color television various other factors, the three wave­ pictures. cinema form displays may not have the same An esse n tial part of the basic tele­ amplitudes at peak white. This would cine alignmen t procedure is the ad­ canada indicate that the combined outputs justmen t of the con trois of the pic­ will not produce a neutral television ture monitor so as to reproduce the picture. After the camera controls gray scale test slide as a neutral (col­ have been adjusted to make the three orless) pattern. Controls are avail­ waveforms match, the two remaining able also in the monitor to vary pic­ projectors can be checked by turning ture brightness and contrast. on their light sources and making the It is a common practice for televis­ necessary adjustments to produce sion technicians to adjust monitor con­ matched waveforms in each case. This trols to give what is considered to be a might be done by altering projector visually acceptable picture. This set up lamp voltages or lens apertures, or by method is adequate so long as the pic­ inserting filters (neutral density or ture monitor is being utilized only for color) in the projector light beams. continuity and program switching pur­ A Canadian company , D. & S. Cor­ poses. But when a telecine is being ley Ltd. of Toronto, also produces used to transfer films and slides to vid­ gray scales and anum ber of other test eotape, the picture monitor should patterns for telecine camera alignment. provide meaningful indications of the MOVEUPTO Among these patterns is a set of six characteristics of the images being re­ vertical color bars for checking the produced. For example, a film with a ARRIFLEX performance of color reproducing sy­ reddish color cast should produce tele­ stems. vision pictures that have a reddish ap­ pearance, and an excessively contrasty film should be reproduced with all de­ Picture Monitor Alignment tail in shadow areas clipped off. It is To obtain a television picture in only in this way that the operator res­ color the combined output signals ponsible for reproducing the films and from the telecine camera are carried slides can make the proper decisions by a cable to a television picture mon­ as to what corrections are needed.