| 摘要 |
A program shutter adapted to close shutter blades having the function of diaphragm blades by a cam member operated with an electric motor has improved control accuracy in high brightness. A blade opening and closing member for opening and closing the shutter blades is urged to open the blades and driven to close the blades by the cam member operated by the motor. Brightness of an object to be photographed is measured by a brightness measuring portion and an area of a plurality of areas of brightness in which the measured brightness is contained is decided by a brightness decision portion. An exposure control circuit starts measurement of the exposure time when the shutter blades are operated to a predetermined trigger point. The cam member is previously moved to the limitation that movement of a blade driving member is not prevented in accordance with the brightness area in which the current brightness is contained before the exposure control circuit generates the exposure end signal. Thus, a closing delay time at time that the blade opening and closing member is moved to close the shutter by the cam member in response to the exposure end signal is shortened. Consequently, the trigger point for starting the exposure control circuit can be established in a position in which moving operation of the shutter blades just before the shutter blades form a pin hole is stable and exposure accuracy is improved.
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