An optical apparatus including a photographic optical unit including a movable optical component for varying a focal length, a light amount adjusting unit disposed in an optical path of the photographic optical unit, the light amount adjusting unit varying an aperture to adjust an amount of light and changing an F-number by varying the aperture, an image pickup device for picking up an optical image formed by the photographic optical unit, a mode switching member for selecting a dynamic image taking mode and a static image taking mode, and a controller. The controller sets different values of the F-number of the light amount adjusting unit in accordance with a state selected by the mode switching member, or varies a moving range of the movable optical component in accordance with a state selected by the mode switching member.