PURPOSE: To obtain a camera system which is provided with the function of a TTL system single lens reflex camera and which is wholly miniaturized to the size of a lens shutter camera provided with an external system observation system.

CONSTITUTION: This camera is provided with the observation system A where a luminous flux from a photographing system 1 is reflected by a 1st movable mirror 2 and a primany object image formed near a primary image-formation surface 3a is formed into a secondary object image near a secondary image- formation surface 8a by an elector system 6 through a 2nd movable mirror 5 so as to observe the secondary object image, and the observation system B which has the same optical axis as the elector system and where an object image formed on a specified surface by an objective system 10 arranged nearer to an object side than the elector system 6 is formed into the image again near the secondary image-formation surface 8a by the elector system 6 so as to observe the object image. In the case of the observation system B, the 1st mirror 2 is retreated from the optical path of the photographing system 1, and the 2nd mirror 5 is retreated from the optical path of the observation system B.