ASAHI PENTAX S3, Service Manual

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Diagram 19
f. EXPOSURE TIMING AT VARIOUS POINTS ON THE PICTURE FORMAT.
In a camera with focal plane shutter, the slit formed by its shutter curtains travels right in front of the
picture format, thereby providing exposure on the film successively. In view of this, it becomes
necessary to measure the time of exposure at various points on the picture formal.
In this camera, the adjustment of the above exposure timing should be made at 1/1000 sec. If the travel
time of the shutter curtains at 1/1000 sec. is consistent and the time of exposure at various points within
the picture format is likewise satisfactory, it follows that exposure timing at the slower speeds is good as
a matter of course.
An ordinary shutter gauge indicates the time of exposure at 3 positions, viz., at starting end, at center
and at finishing end of the picture format.
In view of the characteristics of this camera, it is desirable to adjust the exposure time so as to make it at
the former end of the format slightly faster than at center, and to make it at the latter end as fast as, or
slightly slower than, at center.
By carefully comparing the time of exposure at 3 different positions as indicated by a shutter speed
tester, discretion has to be exercised whether to adjust the curtain speed or the bulb lever. The time of
exposure at the former end has to be adjusted with the bulb lever, while that at the latter end with the
curtain travel speed. However, since adjustment of either of the above parts changes the time of
exposure at the 3 different positions, compare the exposure at the former and latter positions and repeat
the above adjustment procedures until satisfactory results arc obtained. An example in this respect is
shown in Diagram 21.
REFERENCE:
The time of exposure usually referred to means time of exposure at the center of the picture
Diagram 21
3. Assembly and Adjustment of Exposure Counter.
No adjustment is required when no parts are replaced. In the event some parts are replaced, assembly and
adjustment have to be performed in the following order:
Fix the top cover plate (A03), and then the rapid wind lever (C03), followed by the cover ring (C39). The
procedure up to this stage is mechanical.
Then the advance lug actuator (C07) has to be tightly secured with the actuator lug screw (C53). With (C03)
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