In the embodiment of the aperture control system 10 shown in FIG. 1, the data converter 40 includes a processor, a memory, a display, an input device, and a file reading and generating device such as a disk or tape drive or other storage medium, with which to read the CAD aperture file 30 from a disk or tape or other storage medium and to write the converted aperture file 50 to a disk or tape or o