Set the focal length on your lens.
给你的镜头设置焦距。
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。
IF EXIF header information for a 35mm equivalent focal length is available for a clip, the camera focal length will be set automatically.
如果exif头信息35毫米等效焦距在某一段上是有效的，相机焦距将被自动设置。
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