A camera system includes a conventional single-lens reflex function. A camera head includes a finder support section which detachably supports an optical finder unit. When the optical finder unit is attached to the finder support section, the camera becomes a camera system having a single-lens reflex function. In the camera head, a half mirror is provided on the optical path of an image pickup lens. A subject reflected by the half mirror is formed on the side of a finder unit. A subject light passing through the half mirror is formed on an image pickup device. That is, the camera becomes a single-lens reflex camera in which the half mirror is used for a reflex plate.