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February, 1 930
The Motion Picture Projectionist
31
and where this discrepancy is discovered it will be necessary sometimes to use shims similar to that shown at D, Fig. 6, in the front clamp H, Fig. 5. Two of these shims are supplied with each Super Simplex mechanism, one having a thickness of .005" and the other .010". However, one or both of these shims will bring the off standard dimension of these lenses up to standard. It may be interesting to note that the manufacturers of Ross lenses are now making all their outside barrel dimensions the equivalent of the American standard.
With series 2, or half -size lenses of various focal lengths, it will be necessary to use especially designed adapters on the rear element so that the lens may be properly accommodated in the rear lens clamp, G, Fig. 5, and complete data with regard to these adapters will appear in these columns next month.
Mounting Lenses
When setting lenses in the Super Simplex lens mount the following procedure must be observed: By turning the lens focusing knob, K, Fig. 5, set the focusing nut E, Fig. 5, centrally on the focusing thread D, Fig. 5. Loosen the lens clamp screws F and J, Fig. 5. Slip the rear lens adapter B, Fig. 6 (if one is necessary), over the rear combination lens without clamping it on the barrel, as shown in Fig. 7. Slip the lens in through the front of the lens mount and bring it into approximate focus by sliding it back and forth in the mount. When in focus, slightly tighten the front lens clamp screw, J, Fig. 5, so that the lens will not slip. Slip the rear lens adapter B, Fig. 7, along the lens until it centers in the rear lens clamp G, Fig. 5. Loosen the front lens clamp screw J, Fig. 5, and carefully remove the lens. Tighten the clamp screws A, Fig. 6, so that adapter will then be tightly clamped on the rear lens combination.
The lens is then permanently assembled for future use and may be accurately focused by the focusing knob in the regular way. As before mentioned, with some Ross lenses it may be necessary to shim them up in order to bring them up to the standard diameter to clamp them in the front lens clamp H, Fig. 5, and the shims provided should be used for this purpose.
With all Ross lenses there is provided by the manufacturers a shim shown at E, Fig. 6. This shim must always be used in connection with the adapter B, Fig. 6. The length of this shim should be reduced so that it does not project beyond the adapter B, Figs. 6 and 7, or interference will be experienced between the shim and the lens mount. This applies to both large and small diameter Ross lenses.
Series 1 and Quarter-Size Lenses
Series 1, and quarter size lenses of all makes, may be readily accommodated in the lens mount by the use
of adapters especially made for them. With lenses of this type it is necessary to use an adapter similar to that shown at B, Fig. 6. After selecting the correct adapter, slip it over the series 1 or quarter size lens with the threaded portion towards the screen. Select a half size lens tube and screw it tightly on the half size adapter. Your series 1 or quarter-size lens will now have the appearance of a half size lens. Do not at this time clamp the adapter tightly on the lens. Slip the lens, as above assembled, into the mount as set forth for half size lenses, seating the half size adapter B, Fig. 6, under the rear lens clamp G, Fig. 5, and gently lock clamp screws F and J, Fig. 5. The series 1 or quarter size lens may be pushed back and forth in its adapter B, Fig. 6, until it comes into approximate focus. The entire lens should now be removed and the two clamp screws A, Fig. 6, in the adapter tightened solidly on the lens. Insert the lens in the mount in the regular way, tighten screws F and J and focus accurately by turning lens focusing knob K, Fig. 5. Due to the many different designs of lenses it is necessary to select the correct adapters for use in connection with them.
Fixed Focus Clamp
In theatres where proportional size aperture plates or effect masks are used, it is necessary of course to quickly change lenses from one focal length to another, and it is essential that each and every lens used in this connection be absolutely in focus without adjustment on the part of the projectionist when the change is made. Where it is desired to change lenses quickly from one focal length to another this is admirably taken care of by means of an auxiliary lens clamp L, Figs. 5 and 7, which clamps to the lens proper by means of screw N. After the lens is sharply focused, as previously described, this auxiliary lens clamp is simply slipped over the front end of the lens barrel and brought tightly against the front lens clamp as shown at L, Fig. 5, and securely locked on the lens barrel at this point.
It is obvious, therefore, that after this is done any number of lenses once focused and equipped with this fixed focus clamp may be removed and replaced at will in a small fraction of
time, and will always remain in focus.
In order to insure that the lens will always be in the same position with regard to rotation, means have been provided on the auxiliary clamp to always locate the lens in the same position. At G, Fig. 6, it will be noted that there is a hole drilled in this clamp; this hole is so placed that the clamp, when attached to the lens, may slip over the shaft M, Figs. 3 and 5, as will be readily seen upon examining Fig. 3, which shows a lens in position as above described. The lens will always be not only in focus but in the same position rotationally. If shaft M, Figs. 3 and 5, does not project far enough beyond the clamp, H, Fig. 5, loosen the two screws 0, Fig. 5, and slip the shaft M forward until it projects far enough to receive the fixed focus clamp L, Fig. 5; then securely tighten the two screws 0, Fig. 5. It then takes a small fraction of time to change lenses in this manner and, of course, care should be taken always to tighten the lens clamp screws F and J when lenses are inserted in the clamps. A half size lens with rear adapter and fixed focus clamp is shown assembled in Fig. 7.
To take full advantage of the lens mount it will be necessary, where the lens already in use is too short to reach the front clamp and be quickly handled, to add a threaded tubing of standard outside dimensions. In future these extension barrels will form part of the lenses, but where lenses are already in use these extension barrels may be obtained from the National Theatre Supply Co. or the International Projector Corp. The type of lens used, of course, must be stated inasmuch as the threads differ on various makes. When ordering Super Simplex mechanisms the focal length and make of lens shoidd be specified so that correct adapters for Super Simplex lens mounts may be included in shipment. Where Super Simplex projectors are ordered for new installations the size of screen and length of throw should be stated so that the lens manufacturers may furnish lenses properly adapted to fit the mounts. To take advantage fully of the excellent feature of the fixed focus clamp where quick lens changes are necessary, the front end of the lens must be located 10^1" from the film line, and adapter collars may be procured to obtain this length.
B C
L N