Abstract: The present invention provides a camera system having a camera head and a camera main unit, and provides the camera main unit thereof, which are easy to use. Upon attachment of the camera head to the camera main unit, the camera head sends head information about the camera head to the camera main unit. Upon receipt of the head information, the camera main unit rewrites information such as processing variables of the camera main unit. For example, when a camera head incorporating a single focus lens is attached to the camera head, electronic zooming is performed instead of optical zooming in response to a zooming operation performed through a cross key.