| 摘要 |
PURPOSE:To perform the optimum electric eye (EE) correction against the change in F Number of an EE camera, by detecting focal length information in accordance with the change in focal length and changing the driving speed of an electromagnetic driving source, and then, adjusting the opening-closing speed of a shutter acting as a diaphragm also. CONSTITUTION:In a shutter opening-closing speed control circuit 40, when the resistance value of a variable resistor VR1 changes due to the turning of a zoom ring 31, the potential at a point A varies and the output of an operational amplifier 42 fluctuates and, as a result, the terminal voltage of a motor 11 changes. Therefore, the rotating speed of the motor 11 varies and the opening area of a shutter which acts as a diaphragm also becomes constant, and thus, the optimum exposure corresponding to the change in focal length is obtained. Since the time from the moment when a trigger switch 16 is turned off to the moment when a comparator 52 is inverted changes when the resistance value of another variable resistor VR2 fluctuates, second correction can be performed. Therefore, the optimum EE correction can be performed even to an EE camera using two kinds of lenses for telescope-wide angle switching or a vari-focal lens, such as zoom lens, etc.
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