| 摘要 |
PURPOSE:To improve the precision of range finding in a low brightness state and facilitate dimming to a short-distance subject by incorporating a means which specifies the maximum aperture diameter of a shutter all the time corresponding to the subject distance in a shutter device. CONSTITUTION:A cam ring 20a turns associatively with the distance adjustment of a lens barrel 20. This cam ring 20 has different-height cam surfaces corresponding to ranges of, for example, infinity -1.9, 1.9-1.3, 1.3-0.9, and 0.9-0.5 m. Therefore, a driven level 21 which is energized to the cam surface by a spring 25 oscillates around a shaft 22 corresponding to the height of the cam surface. This oscillatory movement allows a member 24 to move left and right in a figure through a pin 23, so parts of a step part 24c formed at one terminal of the member 24 which extend into the movement track of a pin 8 for driving shutter blades 1 and 2 change. Namely, the downward movement of the pin 8, i.e. the maximum aperture diameter of the shutter blades 1 and 2 is specified by the movement of the step part 24c according to the distance ranges. |
