International projectionist (Jan 1943-Dec 1944)

Modern lamp houses are designed to have sufficient ventilation under ordinary conditions, but close control of the amount of air passing through the lamp houses into the stack is essential for troublefree operation. Abnormal draft is caused by excessive ventilation of the projection room, backdraft from certain types of rear shutters having cooling fins, and down drafts from chimneys lacking forced-draft ventilation. Excessive draft, unless very strong, does not usually cause flickering, but it does cause a movement of the arc flame, which becomes noticeable on the screen. The non-rotating high-intensity arc, when properly burned, is almost rectangular in form, with the point of the tail flame directly above and not far behind the positive crater. If the tail flame wavers and is driven toward the front of the lamp house in an intermittent manner, excessive draft is usually indicated. If it is not possible to control the draft with the stack damper, it may be necessary to restrict the ventilation entering the lamp house; or, if the trouble is caused by fins on the rear shutters, the fins may be removed. However, this procedure is not recommended, as the fins were installed to dissipate heat from the film and film-trap assembly. It is suggested that the arc be protected by means of a heat-proof glass shield placed directly behind the rear shutters. It should be remembered, however, that adequate ventilation is necessary to protect the lamp house, and drafts should be restricted only to the point at which the arc will burn satisfactorily. In order to maintain a rectangular arc shape, as described, it is necessary that the carbons be properly positioned, by raising and lowering the negative carbon until the gases are seen to escape from the top of the positive crater. For higher currents, the negative carbon tip should be slightly below the centerline of the positive, and in order to let the gases escape from the top of the crater, it may be necessary to allow the top of the positive crater to burn back as much as 0.32 inch. Anything that distrubs the normal position or function of the arc, such as some types of carbon savers, or by burning the carbons too short, may result in screen discoloration, light reduction, or change in light distribution. The optical system of the non-rotating high-intensity lamp is designed by the manufacturer to deliver the maximum amount of light, and the arc should be operated in a given position with respect to the mirror. Moving the positive crater toward the mirror 0.10 inch from its proper distance will result in a decrease m screen illumination of approximately 40 per cent when using a 7-mm positive carbon. In order to avoid noticeable screen color difference, the arc should be struck three or four minutes before the changeover period and the position of the image of the positive crater should be adjusted before, not after, the change-over. In many theatres where false economy prevails, projectionists are instructed never to strike the arc on the incoming projector until the last minute. With this procedure, screen results are bound to suffer. Lighting Problems When illumination trouble occurs it is necessary to locate it with a minimum of delay. Unfortunately, it is often difficult to determine immediately whether or not the carbons are at fault, and some projectionists keep a few trims in a dry place to be used as a check. Later, if trouble occurs, carbons being currently used are checked against these reserves. If the trouble persists, one may look elsewhere for it, such as in the current supply . or in the condition of the draft. Rarely are the carbons found to be at fault. With the releasing of productions on fine-grain stock, hopes were entertained that some of the lighting problems would be lessened. Experience in this respect has been, to say the least, very disappointing. The greater brilliance and contrast are readily apparent, but the stock used so far has a tendency to buckle. The phenomenon is very curious : it comes and it goes. A print may be used for a few days without trouble ; then, for no apparent reason, the picture on the screen begins to weave in and out of focus. In other words, the photographic image will be out of focus. The modern projector is designed to be adaptable to all types of theatres. There are, however, many mechanisms now in use, particularly in circuit houses, that should have been discarded years ago. Worn film-tracks and hooked sprockets are found in many of them, which are the causes of film damage in alarming proportions. Many projectionists have adopted the practice of speeding up their electric rewinds beyond the limits set by the manufacturers. This causes many fine scratches on the surface of the film, commonly called "rain," and should not be tolerated. It is difficult to understand why so many owners and managers will not hesitate to make large expenditures on new marquees, carpets, chairs, and on the general beautifying of the auditorium, all of which can not be fully appreciated in the dark, but neglect to maintain properly the most vital part of their theatre — the projection equipment. The screen is allowed to become dirty and discolored. There are many methods of so-called resurfacing; few have proved satisfactory. The best procedure is to try to keep the surface and perforations free from dust and dirt. When discoloration does take place, the screen should be replaced. The difference in cost between an ordinary resurfacing job and a new screen is not comparatively great. Many of the older theatres were constructed during the days of vaudeville and (Continued on page 25) Presenting: Orin M. Jacobson ORIN M. JACOBSON. Born November 28, 1891, in Marinette, Wis. Family moved to Tacoma. Wash., in 1897. After graduating from Tacoma High School went to work as marine fireman to satisfy yen to become an engineer. Evidently found an engineer's career not to his liking, for one year later he returned to Tacoma where the lure of the theatre got him. Became an apprentice projectionist at the old Bijou Theatre in 1910, working at that time with a No. 5 Powers machine and using two garbage cans for take-ups. Joined Local No. 175 in July, 1910, and since then has served in every office of the organization from sergeant-at-arms to president. Since 1919, he has been a delegate to all I. A. Conventions. Has been secretary of District Number One since 1926, and in 1930, was appointed I. A. representative by William F. Canavan. an office he still holds. His hobby is editing and publishing the District Quarterly Bulletin. Married and has a daughter and one grandson. This is the sixth in our series of who's who in the projection world. From time to time, I. P. will present to its readers brief word portraits of leading figures in the craft. — Ed. 12 INTERNATIONAL PROJECTIONIST