Projection engineering (Jan-Dec 1931)

Page 10 PROJECTION ENGINEERING tographed. Projectionists have had wide leeway in framing and no guide to show them when their proportional aperture was centered until they saw heads or feet cut off on the screen. Microphones can be lowered from three to five feet, resulting in an obvious advantage in sound quality and convenience for the sound department. Camera lenses can be recentered on the new aperture for better optical coverage. Advantages in the Theatre 1. All pictures can be projected through a single standard aperture, doing away with movable flippers and changes of screen masks, aperture plates and lenses during the show. 2. The frame lines just outside the aperture as they used to be for silent pictures will be a help to the projectionists in keeping in correct frame. If the picture should momentarily go a little out of frame the projectionist will be warned by seeing a frame line, but as the lines are wide the misframe can be corrected before the audience notices it. 3. Standardization of exact dimensions by the studios will give the projectionist more uniform prints from the various companies. 4. Theatres now using reduced proportional apertures will gain four per cent more screen image without additional magnification. 5. Theatres now using the movietone aperture or the old silent aperture will gain the advantage that the studios can fill the whole area of the new standard aperture with essential dramatic action and will not have to leave a border of unimportant picture. Equipment Changes Required in Studios In Cameras. New apertures at a cost of about $25 per camera; new ground glasses; adjustments to recenter lenses. In Laboratories. Minor adjustments depending on the present practice followed by the laboratory. In Art Departments. New camera angles. In Viewing Rooms. Adjustment of projector apertures and screens. Equipment Changes Required in Theatres 1. Theatres now using reduced proportional apertures : a. File out apertures to larger size or insert new plates. b. Enlarge screen by about four per cent of area. 2. Theatres now projecting in movietone proportion : a. Insert new aperture plates. b. Either move the screen masks in from the top and bottom. c. Or, install shorter focal length lens and widen the screen. 3. Theatres now projecting full frame silent or full frame with disc sound : a. Insert new aperture plates. b. Recenter head of projectors.' c. Either, move screen masks in on all sides. d. Or, install shorter focal length lens to enlarge image to present screen. Detailed Specifications for Proposed Standard Specifications for the standardized apertures as worked out by the subcommittee in consultation with studio and equipment company technical representatives are shown in the attached drawings. Camera Aperture The dimensions indicated in Fig. 1 provide the maximum aperture which will leave an adequate margin of safety. It should be emphasized, however, that laboratories should print both picture and sound track with the greatest possible accuracy. In the drawing the center line of the right-hand side sprocket holes is used as the base center line for calculating all dimensions, since cameras and printers register at this point. Projector Aperture The projector aperture dimensions, Fig. 2. Academy standard projection aperture. Fig. 2, have been stated on the basis of projection on the level as no uniform provision for the keystone effect can be made. The calculations have been carried out with due regard to the fact that in projectors the film is controlled at its right-hand edge. Sound Track The drawing, Fig. 3, is a detail from Fig. 1 to show the minimum requirements for sound track width and location which were agreed upon by the heads of studio sound departments and incorporated in the subcommittee specifications. Minimum and Maximum Sound and Picture Areas Fig. 4 is a composite view of the dimentions resultant from the calculation of shrinkage and mechanical tolerances from which Fig. 1 was derived. Some of the factors and conditions considered are given in the following analysis by J. A. Dubray of the subcommittee: fc. 243" U— SOUND TRACK ~1 CD CD CD -< — .104" MIN. CD CD , <— .004" MIN. CD CD CD CD CD CD CD CD CD . i «— .050" MIN. — H U— .100" MIN. Fig. 3. Detail of minimum requirement for sound track. 1. For Negative Films — a. The plus and minus camera tolerances which include the location of the aperture (constructional tolerances), the size of the aperture (constructional tolerances) and the side weave of the film on the register teeth of the intermittent mechanism. b. The plujS and minus tolerances which must be allowed in accumulating the camera tolerances with a J4 per cent film shrinkage. 2. For Positive Films, c. The plus and minus tolerance required in printing a positive and calculated first from the effect of registering the positive film against the right-hand side of the teeth of the main printer sprocket while the negative registers against the lefthand side ; second from the effects of registering the positive and the negative films in the opposite direction. Both cases for unshrunk positive and accumu