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and the leading edge of the second curtain form a slit as they traverse the film aperture. The more narrow the slit (shorter interval before release of second curtain) the shorter the exposure; the wider the slit (longer interval between release of first and second curtain) the longer the exposure. Accurate exposure (slit width) is mechanically controlled by cams and levers. At the slower speeds (1-second to 1/30-second) an escapement is engaged and further delays release of the second curtain. At shutter speeds of 1/50-second and slower, the first curtain completely uncovers the film before the second curtain is released. When the shutter is wound both curtains lie approximately 7-millimeters behind the edge of the film aperture. When the shutter is released the curtains travel together for approximately 4-millimeters, at which point the second curtain is arrested. The trailing edge of the first curtain enters the film aperture approximately 12-milliseconds after release of the shutter. The time required for the curtain to traverse the aperture is approximately 17-milliseconds (1/59-second). The shutter curtains, overcoming inertia during their travel, move faster as they cross the film aperture. To assure even exposure of the film, the slit must widen as the curtains move across the aperture. This is accomplished by the increasing diameter of shutter curtain and ribbon rollers as material is wound on them, and by different tensioning of the shutter springs. A brake mechanism applies a gradual braking action to the shutter curtains as they near the end of their run. This prevents an abrupt stop of the curtains and lessens camera vibration.

a. Shutter Winding (fig. 1-2, 1-3, 1-4, 1-5, 1-6). The shutter is wound and the film advanced one frame by operating the winding lever through a complete stroke. The shutter may also be wound by completing a stroke cycle with a series of short intermittent strokes of the winding lever.

Figure 1-2. Film Transport and Shutter, Schematic.

(1) The driveshaft gear (fig. 1-2) rotates counter-clockwise as the winding lever is moved through its operating arc. Intermediate gear A meshes with gear C of the sprocket wheel shaft.

(2) Two stop discs on top of gear C , in conjunction with two stop levers (fig. 1-3), control the stroke of the winding lever, film advance and exact shutter winding.



Figure 1-3. Shutter Winding and Speed Controls.

(3) The lock lever, resting on intermediate gear A (fig. 1-3), prevents reverse rotation of the sprocket wheel shaft if the winding operation is interrupted.

(4) The lower gear (fig. 1-2) on the sprocket wheel shaft meshes with two-part intermediate gear B which engages a gear on the main shutter roller shaft. Operation of the winding lever rotates the main shutter roller through the gears. This simultaneously winds the second curtain on to the main roller; and by shutter curtain ribbons, pulls the first shutter curtain across the film aperture and tensions the springs of the spring rollers.

Figure 1-4. Controls in 1-Second Position, Shutter Wound.

(5) When the shutter is fully wound (fig. 1-4), one of the lower ends of the spring-loaded double-stop lever engages a notch on the under-side of the drives haft gear. This prevents the winding mechanism from being overdriven.

b. Shutter Speed Adjustment. Shutter speeds are selected by setting the shutter speed dial to the desired index. This adjusts the shutter control cams and levers which regulate the release of the second shutter curtain and consequent slit width.

(1) Shutter speed dial set for B . Figure 1-3 illustrates the position of shutter control cams and levers when the shutter is wound. The slow-speed escapement is disengaged. The shutter slit adjusting and arresting levers are positioned to prevent release of the second shutter curtain while the shutter release is depressed.

(2) Shutter set for 1 to 1/30-second (fig. 1-4). The speed cam renders the adjusting lever inoperative. The setting cam positions the adjusting guide lever and pivots the slow-speed escapement around its axis. A segment gear is actuated by a catch on the main shutter roller shaft. The slow-speed escapement controls the delay of the second curtain. The slow-speed escapement anchor is deactivated by the disengaging lever at 1/15-second and 1/30-second shutter speeds.

(3) Shutter speed dial set for 1/50 to 1/1000-second. At speeds between 1/50-second (electronic flash symbol) and 1/1000-second the slow-speed escapement is disengaged. The speed cam positions the adjusting lever according to the selected speed, and the highest point on the cam (fig. 1-8) sets the shutter for 1/1000-second. The dropping flank, (fig. . 1-3) on the main shutter roller shaft, actuates the adjusting lever which rests against the arresting lever B eccentric shaft. Figure 1-8 illustrates component positions for 1/1000-second.

c. Shutter Release






Figure 7-5. Shutter Release, Schematic.