The system aperture, often the entrance pupil or the aperture stop, limits the rays that can enter the optical system from the defined field.

系统孔径，常指入瞳 （entrance pupil） 或孔径光 （aperture stop），它限制可从已定义视场入射光学系统的光线。

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The results show that the dynamic spatial resolution in time direction has been improved by 15-20% when the aperture stop width is properly enlarged.

分析结果证明，在适当扩大孔径光栏宽度后，在时间方向上的动态空间分辨率可提高15～20％。

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Usually one can first meter using a larger aperture (so that the metered exposure time is under 30 seconds), then stop down as necessary and multiply the exposure time accordingly.

通常，你可以用大点的光圈测光(这样，测量的曝光时间就在30秒以内)，随后缩小光圈，相应地增加曝光时间。

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