Abstract: In a preferred embodiment, a camera convertible from a camera employing normal-focusing lens for picture-taking, to and from a camera employing telescopic lens, within a unitary housing, having the lens mechanism slidably movable intermittently as desired between the two alternate states, with the lenses shutter mechanism being a structure in fixed position behind the lens, in a predetermined position to alternately block exposing focused light and to transmit exposing focused light to an exposable film posterior to the lens shutter mechanism, the mechanism being a pivoted door structure spring-biased to a closed state of light-blocking function, actuatable intermittently to a light-exposing state by cocked force-exerting member acting through a slip-clutch mechanism.