A rangefinder mechanism is shown in which the scanning mirror has been reced with a movable scanning optic. The automatic rangefinder system includes a pair of optical paths one a reference path and the other a scanned path which are led to impinge upon a photosensitive surface for comparison purposes. The output of the photosensitive surface is used to adjust the main lens of the camera. Disposed in front of the movable optic is another optical movable relative thereto to coordinate with the position of the main lens of the camera as feedback and adjust the rangefinder system.