| 摘要 |
For a given shutter size, the effective illumination or light transmission period is increased by one half that of the angles subtended by the aperture. This increase is accomplished by providing, in addition to a first shutter having an opaque section in the case of a camera of at least 180 DEG , a second shutter having an opaque section of an angle equal to that subtended by the aperture. The second shutter is coaxially mounted with the first shutter and caused to rotate at twice the speed of the first shutter. By initially aligning the leading edges of the shutters with the start of the aperture, the aperture is effectively covered and uncovered in half the time which would normally be required by using a single shutter providing the same film transport period alone. As a consequence, the period of illumination is increased by the referred to one-half of the angle subtended by the aperture. This value becomes significant if the shutter diameter is small relative to the aperture size since the subtended angle becomes larger.
|
