A single lens reflex camera includes a vertical open topped U-shaped bracket mounted in the camera body below the pentaprism, a forwardly located lens mount separably coupled to an objective lens and pairs of links mutually pivoted between their ends connected between the bracket arms and corresponding edges of the lens mount to support the latter in a fixed orientation for linear longitudinal movement along the camera optical axis. A light tight collapsible conduit extends between the camera body and lens mounts and includes telescoping members with relatively slidable side and bottom walls and an accordian top wall. A rack carrying slide arm projects rearwardly from the lens mount and is engaged by a motor driven gear to longitudinally shift the lens mount. The motor is controlled manually or in response to a focus detecting device and the lens mount may be motor advanced and retracted or motor advanced and spring retracted. The lens diaphragm is automatically stopped down by a camera housed mechanism and diaphragm control information is transmitted from the lens mount to the camera body.