The invention relates to a compact two-group zoom optical system which has an angle of view of 70\xb0 or greater at the wide-angle end and satisfactory image-formation capability all over the zoom range while maintaining a zoom ratio of 3 or greater. The contone CMYK data and bi-level black data are expanded in parallel operations. The tiltable member 20 is disposed in a cavity 41 formed inside the cap 40. The first and second magnetic drive members are magnetically coupled to each other so that the blade is drivingly coupled to the drive motor. These compositions may be directly incorporated into the locus to be protected or may be applied to a structure in a coating.