A group of optical elements of a zoom lens unit has variable-focal-length lenses whose optical properties can be adjusted. A camera having this zoom lens unit incorporated therein includes a program memory which stores therein a plurality of mocking design data with respect to a group of parameters having any of a plurality of variable design parameters for the zoom lens unit. The camera also has a control unit into which designation information is inputted by the user which designates any one of the plurality of mocking design data and a control unit which controls the variable design parameters based on the mocking design data designated by the designation information, so that a desired optical property can easily be obtained.