| 摘要 |
Photographic camera such as a reflex camera, of the type having at least one automatic region in which the diaphragm blades of a diaphragm blade aperture system, incorporated in the objective lens arrangement connected, e.g. in front of a light sensitive element for sensing ambient light, are adjustable from an initial position corresponding to the smallest diaphragm aperture width to a diaphragm aperture width adequate for the prevailing light conditions, in dependence upon such sensed ambient light, by means of a driving member or driving ring of an energizable driving system for the diaphragm blade aperture system which is energizable with electrical current pulses, e.g. via an electronic control circuit, in a continuous progressive adjustment movement, such that the continuous progressive adjustment movement of the diaphragm blades is effected under the continuous sliding frictional contact resistance of a spring loaded friction brake acting against the driving member for the diaphragm blades and securing the driving member simultaneously in the corresponding adjustment end position attained, e.g. in dependence upon such sensed ambient light, and which friction brake at the end of the camera exposure operation, i.e. after taking the photograph, is temporarily disengageable electromagnetically from its operative frictional contact position to permit the delay free, i.e. frictional contact free, return of the diaphragm blades back to the initial position thereof.
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