Sonar responsive shutter blade time out control circuit

An exposure control circuit for controlling the maximum time out period for an exposure interval in a photographic camera apparatus of the type including means for defining a film plane, means for transmitting light from a scene along an optical path to expose photosensitive film located in the film plane, and an exposure control system for allowing the passage of scene light along the optical path to the film plane to define an exposure interval, said circuit comprising:

• clock means for providing a train of clock pulses;
• first counter means for counting said pulse train and providing a total pulse train count corresponding to the camera-to-subject distance range;
• second counter means for counting said pulse train and providing a pulse train count which commences generally in synchronism with the initiation of the exposure interval;
• and
• logic means responsive to said first counter means providing a pulse train count corresponding to a camera-to-subject distance less than a select camera-to-subject distance for enabling the decode of said second counter means to provide an exposure interval termination signal upon said second counter means reaching a pulse train count corresponding to a select maximum exposure interval time out period, and further responsive to said first counter means providing a pulse train count corresponding to a camera-to-subject distance greater than said select camera-to-subject distance for enabling the decode of said second counter means to provide an exposure interval termination signal upon said second counter means reaching a pulse train count corresponding to another maximum exposure interval time out period greater than said select maximum exposure interval time out period.