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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Under those conditions photographers shoot with a fast exposure time and small aperture. That makes it impossible to capture faint objects in a dark background, such as stars.

在这种情况下拍摄者会使用很短的快门时间并调小光圈，这样就不可能拍摄到黑色背景上那些很暗的物体，如星星。

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It has a wide-aperture lens to capture as much light as possible, and the technology requires no clunky auto-focus mechanism. It adjusts exposure time automatically.

它的大光圈镜头可以摄入尽可能大的光量，所用技术并不需要笨重的自动对焦系统，曝光时间也是自动调节。

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