Single lens reflex camera system capable of TTL flash output control

In a system for taking pictures which is capable of flash photography and which includes a movable mirror device formed with a light-transmitting portion, the mirror being movable between an observation position in which the mirror reflects light from a phototaking lens to a view finder and also transmits the light from the phototaking lens through the light-transmitting portion, and a photographing position retracted from the photographing light path;

• a light receiving device positioned to be capable of receiving the light transmitted through the movable mirror device and the light reflected by a film surface, the light receiving device generating a photoelectric signal corresponding to the quantity of the received light;
• a trigger circuit for firing a flash tube in synchronization with exposure of the film surface by the light;
• and a flash unit having a flash output control device for controlling the quantity of light emission of the flash tube in response to the photoelectric output;
• the improvement comprising:
• means for arbitrarily actuating said trigger circuit when said movable mirror device is in the observation position, the actuating means including means for correcting the response of said flash output control device to said photoelectric output in accordance with the difference, with respect to the same object, between the light quantity incident on said light receiving device when the movable mirror device is in the observation position and the light quantity incident on said light receiving device when the movable mirror is in the photographing position.