To obtain the shutter speed of a designed shutter mechanism, dispensing with a trial working of the shutter mechanism.

A three-dimensional CAD program, a motion analysis program and a shutter speed conversion program are used, and the image data of the shutter mechanism is formed by the three-dimensional CAD program, and the image data is inputted to the motion analysis program, then, the motion is analyzed, then, the analysis result of the motion analysis program is inputted to the shutter speed conversion program, so that the shutter speed of the shutter mechanism is obtained by calculating.