In an interchangeable lens camera, a lens may be mounted on an aperture of a so-called body-side mount on a front surface of a camera body. One of variables of a body-side mount is a flange back distance. A flange back distance is a distance from a reference plane of a body-side mount to an imaging plane of an imaging device. The reference plane is a plane where a rear end of a lens makes contact with the body-side mount. A body or a body-side mount may have a flange back distance unique to itself. An interchangeable lens may be designed for a flange back distance of a body or a body-side mount on which the interchangeable lens is to be mounted.
So far, in order to use a lens having a longer flange back distance than a flange back distance unique to a body, an intermediate adapter may be attached to the body-side mount for adjustment of the flange back distance (for example, refer to Patent Literature 1).