Camera shake rule: The slowest shutter speed at which you can safely handhold a camera is one over the focal length of the lens in use.

手持拍摄时，最低安全快门速度为所用镜头焦距的倒数，低于这一速度，相机震动可能导致照片的锐度下降。

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A good rule of thumb to minimise camera shake is to set the shutter speed at a minimum of one second divided by your focal length.

测算你相机的安全快门速度有一个好的方法，你相机镜头焦距的倒数，就是你避免镜头抖动的快门最小值。

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