PURPOSE: To provide a system which is compact, inexpensive and light in weight when a camera system is constituted of a lens barrel of a type that a diaphragm is provided in a lens and a camera body.

CONSTITUTION: The camera system is equipped with the camera body 300, a freely attachable/detachable N-type lens barrel, an L-type lens barrel 100 which has a long flange back and is freely attached/detached via an intermediate adapter 200, a focusing mechanism provided in the N-type lens barrel, the diaphragm 103 provided in the L-type lens barrel 100 and driven by external force and a diaphragming mechanism provided in the intermediate adapter 200 and transmitting the driving force of a driving mechanism on the camera body side to the diaphragm 103. When each lens barrel is attached, the signal of the attachment is transmitted to the camera body side to enable driving for focusing and diaphragming based on the signal of the attachment.