PURPOSE: To shorten the starting time by providing a means which gives the phase control to a rotary shutter in response to a synchronizing signal and a means which decides whether the shutter phase is coincident with the shutter speed.

CONSTITUTION: When a shutter 1 is started, a switch 13 conducts by a start control signal S supplied to a terminal 20. A capacitor 15 is charged up to the maximum value V4 and the output of an operational amplifier 16 is also set at V4. Thus a motor 17 is driven to open and close the shutter 1. A closed loop is formed with a photoelectric conversion system of a photocoupler A via a reflector 3 for photocoupler. Then the phase of a shutter blade 2 is kept constant together with a vertical synchronizing signal VD. A phase deciding circuit 18 decides whether the phase of the shutter 1 is coincident with the exposure time.