Abstract: A single-reflex camera is provided with a movable mirror provided on a photographing optical path; a driver circuit connected to an electrical motor so as to drive the movable mirro, the driver circuit being arranged to cause the movable mirror to move out of the photographing optical path in a first cycle of driving prior to exposure and to cause the movable mirror to move onto the photographing optical path in a second cycle of driving following the first cycle of driving; a photometer circuit arranged to receive a portion of the light flux which passes through the photographing optical path and which is incident upon the movable mirror and then to generate information concerning the brightness of an object; a first timer circuit for counting the time period required for the first cycle of driving of the driver; and a second timer circuit for determining, on the basis of the required time period counted by the first timer circuit; the time interval between the starting of the first cycle of driving of the d