The Exhibitor (1953)

may also be used in the presentation of standard film fare, it should be remem¬ bered that metallized screens are specular, and therefore have a tendency for light fadeaway toward the edges. Although no specific screen has as yet been designed for 3-D and 2-D presentation, manu¬ facturers are working on the problem and it seems likely that a surface giving satisfactory results for both types of pro¬ jection should be developed. For those exhibitors who do not wish to install a new screen, a recent report of the Motion Picture Research Council stated that the proper screen conditions for the presentation of three-dimensional films may be obtained by spraying present mat screens with suitable metallic paints. At the present time there are two ac¬ cepted methods of synchronizing projec¬ tors, and both are fairly simple and in¬ expensive. The more expensive installa¬ tion makes use of an electrical interlock¬ ing device. A Selsyn motor is mounted on each projector and the machines are synchronized through their motors. Such a system would cost an exhibitor about $700. Mechanical interlocking offers a less expensive method, and there are a num¬ ber of ways in which a projector may be synchronized by mechanical means. One method involves rigging a shaft across the front wall of the projection room with sprockets at each end. If the sound heads are of a type which permit it, sprockets are then similarly fitted to them and connected to the wall shaft with chains. A mechanical synchronizing device is also available which makes use of flexible cable that operates a small twogear train at each end. This type of inter¬ locking device may either be connected to the shutters or soundhead, depending on the type of equipment. One advantage this mechanical means has over the elec¬ trical interlock is that it may be dis¬ connected easily, leaving the machine free for conventional films, and just as easily reconnected. With the electrical method the projectors must be left as they are in order to maintain the synchronization. The final decision of which interlocking device to use must rest with the indi¬ vidual exhibitor’s preferences and pocketbook. Concerning the power problem gener¬ ators and rectifiers should be checked in order to determine whether or not they will stand the load of handling the two machines for the 50 minutes it takes to run each set of reels. In many cases an additional rectifier or generator will have to be purhcased. It is also recom¬ mended that the wiring be thoroughly checked to see if it is capable of handling the additional load. Exhibitors will nat¬ urally find that their power bills will show an increase. It will be necessary to purchase from four to six 24-inch reels in order to be able to have as few intermissions as is possible while rethreading. In some sit¬ uations the booth may have to undergo some changes to be able to accommodate these large reels. The 24-inch reel repre¬ sents about the limit of capacity for booths and projectors. They will hold up to 5,000 feet of color film, or approxi¬ mately 5,500 feet of black-and-white, and will require 25-inch magazines on the machines. This reel capacity would per¬ mit a theatre to show a maximum pro¬ gram of about 110 minutes with one in¬ termission for reel changes. It is also estimated that a reel this size would weigh about 30 pounds when loaded with color film. The polaroid filters for each projector port must be installed in such a manner that the light beam goes through the center. It must be remembered that the filter for the left port has a directional characteristic different from that of the one used on the right port, and the two must not be confused. Warner Theatres has issued detailed Selsyn motors were attached to each machine at the Aldine, Philadelphia, to synchronize the projectors for three-dimensional pictures. instructions describing the method which they recommend for the proper installa¬ tion of these port filters. “Each frame consists of one bar with rings and one bar with clips. The bar with rings is the upper bar. Locate the center of your light beam. The upper bar is to be located in such a fashion that the polaroid filter will be centered on the light beam. It is also absolutely essen¬ tial that the top bar be levelled. Use a spirit level in locating the upper bar accurately. Mark the shutter guides ac¬ cordingly. Mount the upper bar accord¬ ing to these markings by drilling and tapping the shutter guides and drilling the bar. Insert the polaroid filter in the lens. Mount the bottom bar without levelling. Leave sufficient clearance on bottom so that the filter can easily be released for cleaning and running regular film.” Operators will have to be carefully in¬ structed in the proper operation of the equipment. Threading must be very ac¬ curate and the correct reel must be placed in the right machine. If the synchroniza¬ tion is even one frame off, the illusion is lessened and eye strain results. The problem of splicing if there is a break in the film is another which must be handled carefully. Glasses In addition to all the other pieces of equipment the theatre must of course have polaroid glasses for the audience. As with almost everything in the current 3-D situation no definite or “correct” procedure has been developed as yet. Houses showing “Bwana Devil” have been using glasses with cardboard frames which are discarded by the patron after use. It is usually estimated that these temporary glasses cost anywhere from eight to ten cents. One suggestion that has been made to help defray the cost of these glasses is the selling of advertising on the frames. In addition to the temporary type of glasses, some houses, particularly those showing the Stereo-Techniques program, have been using permanent glasses mounted in plastic frames similar to those found in sun glasses. These may be rented, or purchased at a price of about one dollar a pair. It is suggested that a theatre supply itself with two and onehalf times the number of seats. There¬ fore, a 1,000-seat house would need 2,500 pair of glasses. ( Continued on page PT 17) How Natural Vision Functions PROJECTORS Jlmoget or* photographed from two different point! of view, just at they ore teen in nature. Each lent, focuting and con¬ verging on on object almott precisely ot do the human eyet, providet o teparote and complete 2 dimentional picture. In the theatre, the normal two projector! in o booth project the two teparote picture! onto the tcreen in tuperimpotition, much at in nature they ore projected onto the 'brain eye' (tee diogram). The right ond left imaget pott through Polaroid light filter! placed in the portholet of the projection booth. ^^The two imaget are tuperimpoted almott at one on a reflec¬ tive type tcreen. ^^Th* imaget are reflected back to the viewer who it equipped with Polaroid glouet, which serve to accept the correct image intended for each eye, while rejecting the image not intended for that eye. PT-6 PHYSICAL THEATRE DEPARTMENT of EXHIBITOR March 4, 1953