Automatic control apparatus for photographic camera

摘要

In an automatic diaphragm stop down operation square wave pulses are generated, the number of which represents the extent of diaphragm stop down. Short pulses are generated responsive to the leading and trailing edges of the square wave pulses. The short pulses are counted. After a predetermined number of short pulses are counted, diaphragm stop down is arrested. In one embodiment, when a periodic input signal representative of the extent of diaphragm stop down rises above a first threshold, the square wave pulses are produced at a first level and when the input signal drops below a second threshold lower than the threshold, the square wave pulses are produced at a second level.