PURPOSE: To set desired brightness easily through lever operation by using a Hall element for the diaphragm meter part of a lens to detect the state of a diaphragm diameter, varying the voltage applied to a lens stop, and slowing down variation of the lens diaphragm as the lens diaphragm is closed.

CONSTITUTION: The lens diaphragm 103 enters opening/closing operation depending upon the motion of the pointer 204 of a meter 104. The voltage applied to the meter 104 is generated by a voltage generating circuit part 106 provided to a remote control part side and sent to a voltage varying circuit part 105 through a signal line 203 to apply the meter part 104 with the voltage corresponding to the current diaphragm diameter through a signal line 203. A magnetic body 102 is fitted to the lens diaphragm 103 and moves as shown by an arrow according to the opening/closing operation of the lens diaphragm 103. The Hall element 101 is close to the magnetic body 102 and also arranged fixedly to send the output corresponding to the motion of the magnetic body 102 to the voltage varying circuit part 105 through a signal line 201, and the voltage from the voltage generating circuit part 106 is varied according to the lens diaphragm diameter and applied to the meter.