When the user presses the trigger button, a rod is pulled longitudinally by a drive spring in a first direction from a first to a second position triggering the shutter in the process and a coupling thereafter couples the rod to a transport motor which returns the rod in the opposite second direction back to first position, the rod resetting the shutter in the process, the rod when returned to second position becoming decoupled from the motor so that the latter will not oppose the force of the drive spring for the next first-direction movement of the rod. The crank rod is blocked against first-direction movement by two blocking levers, the first initially being in blocking position and the second initially in unblocking position. When the user presses the trigger button, the first blocking lever unblocks the rod and the latter performs its first-direction movement, the first lever remaining in unblocking position until the user releases the trigger button, and near the end of the second-direction movement of the rod the second blocking lever snaps into blocking position, to prevent an unintentional second exposure, the second blocking lever blocking the rod until the first lever, upon release of the trigger button, can return to blocking position, whereupon the second lever once more assumes unblocking position. When instead of single exposures exposure sequences are to be made, the user sets a manual switch which arrests the second lever in unblocking position, so that the rod performs its first- and second-direction movements alternately for as long as the user keeps the trigger button depressed.