International projectionist (Jan 1941-Dec 1942)

a.> t tie capacity of the slide-board. For action shots or exposures of short duration the two pictures must be made simultaneously. Apparatus for action shots may be made up of two cameras mounted on a common base and so arranged that the iiUerocular may be varied by moving i.ne or both cameras. The shutters must be accurately synchronized and the .timing of the shutters closely matched. The requirements for making still stereograms apply also to motion picture stereoscopy. For instance, in scientific films it may be necessary to photograph a very small object, such as an insect, quite close to the camera. This demands a very narrow interocular. On the other hand, some scenic shots are vastly improved by spreading the lenses apart, thus obtaining a greater three-dimensional effect. Limited Range Obviously it is difficult, if not impossible, to build one camera with such a wide range. Several cameras may be required to cover a wide variety of subjects. Since photoplay production does not demand the photography of minute objects, it seems reasonable to assume that only a limited interocular range will be needed. A range of interocular from IV2 inches for close-ups up to 4 inches for long shots should be adequate for the average photoplay. It is possible to pro\ide this range in one camera. The same desirable features regarding convergence of the picture centers in making stereo movies, because "bordering," that is, establishing the proper margins at right and left, must be done. and can be done, only in the camera. The finder on a stereoscopic motion picture camera is an important accessory, aitd its functions differ in some important respects from standard practice. It is desirable to view the scene in three dimensions and to see both images so that proper alignment for convergence and bordering can readily be effected. Naturally the finder images must be right side up and not reversed left for right. A binocular finder of the right kind enables the cameraman and director to determine by visual means the lens interocular considered best for any given scene. Of course, general rules must be established for interocular spacing depending upon distance of principal object and magnification of the lenses employed, but occasionally it may be desirable to increase the depth of a scene to enhance its dramatic effectiveness. No data are included in the present paper on interocular spacing versus distances and magnifications because there is little agreement among research men and operators as to recommendations. Everybody agrees that "excessive" interocular spacing creates distortion. The controversial point is to define the words "excessive" and "distortion" as applied to the problem. Broadly, the whole matter of interocular spacing and magnification in the taking of the scene should be influenced by the Conditions of proj( etion under which the picture will be shown. Therefore, it is of great value to know beforehand 'what will be the average conditions of screen angles, seating arrangement, etc. John T. Rule, of Massachusetts Institute of Technology, has contributed valuable data on the geometry of stereoscopic projection in a recent paper. Projection The projection of the Polaroid threedimensional 35-mm motion pictures that have been mentioned has been done through two synchronized projectors. In one case synchronism was obtained by electrical interlock; in the other, by mechanical means. Both systems worked excellently. Since projection of the pictures was on a "grind" basis, with very short periods between shows, and there were no breakdowns, it is evident that either method is satisfactory. Considerable experimental work has been done with 16-mm projection but no actual use has been made of 16-mm stereograms for commercial purposes. The indications are that such equipment will be available sometime this year. Several types of stereoscopic still projectors have been introduced, and the three-dimensional projected still picture is coming into wide use for display and advertising purposes. Types of Projectors At present there are on the market two types of projectors using Polaroid and one using the "eclipse" system. One ol those using the Polaroid method projects stereograms consisting of pairs of standard 3 X 4-inch lantern-slides; the other is equipped for both 2 X 2-inch slides and 35-mm slide-films. All these projectors employ dual optical systems. One type uses two lamps, and the projector for slide-films uses a special lamp containing two filaments. These new projection facilities should be of interest to the scientist as well as the advertiser. The medical profession can utilize them for many purposes. Gross specimens, operations, and radiographs may be enlarged in three-dimensional form and may be viewed by large groups. Engineers can obtain photoelastic records obtained by polarized light in three-dimensional form to facilitate the study of stresses and strains in the various planes of the plastic model. Any number of other interesting possibilities present themselves. PROJECTIONIST INVENTOR Toledo, 0. Lawrence Aubry, local operator, has invented an auto burglai alarm guaranteed to scare the pants off car thieves. He conceived the idea wliil; r: pairing a short circuit m a projector. The device gives off a toot of the horn ai the slightest nudge and a ripsnorting toot as the nudge is increased. Aubry has applied for a patent on his invention. GOVERNMENT WILL BUY USED 16MM PROJECTORS Washington. — Owners of 1939, 1940, and 1941 model sound projectors for the showing of 16 millimeter motion pictures were asked last week by the War Production Board to offer them for sale to the Government. These machines are essential for the rapid teaching of the Armed Forces and defense workers. Due to the present aluminum shortage, production of new projectors, which requires the use of aluminum casting, is being curtailed. Approximately 35,000 16mm. sound projectors were manufactured in 1939, 1940, and 1941, and sold for various purposes. Many of the purchasers were large corporations, such as automobile companies, which used the machines for sales promotion. Any private individual, business organization or school owning such machines is requested to write to the WPB, stating the number of machines he owns, how many he is using for defense training, and how many he is willing to sell, the year model or models, and what price he is asking for them. The WPB will not itself buy the machines but will transmit the information to the War and Navy or other Government departments who can then buy the machines they need. MOVIE ATTENDANCE UP Theatre attendance this year, under the spur of continued expansion in employment and payrolls, will show a gain exceeding that of last year when an advance of 10 pe>cent was scored, according to the current survey of the film industry by the authoritative Standard & Poor's. The survey says in part: "Movies should benefit particularly from the war. The public, with the largest income in years, now finds many of its customary dhersions either drastically reduced or virtually eliminated by the war. PROJECTIONIST BURNED Winchester, Ky. — Ernest Kitnbrell, projectionist at the Town Hall, was burned about the head and arms when a roll of filrr. broke and caught fire in the booth. He spent one night at a local hospital after being treated. In the theatre at the time of the fire were about 200 patrons. They were directed safely to the exits by Manager Dallas Hall and Charles Burton, ticket taker. 17,919 THEATRES IN U. S. According to a recent survey there are now 17,919 picture theatres in operation in this country — an increase of 378 over 1940. The average seating capacity is 517, with houses located in 10,013 towns and cities. JANUARY 1942 11