焦距长度是当相机焦点对在无限远时，镜头的后侧主点到CCD平面的距离。
曼富图303云台还可允许用户设定相机旋转角度和配套的镜头焦距长度。
The Manfrotto 303 also allows the user to set the degree of camera rotation set in relation to the focal length of the lens being used.
广角镜头：覆盖范围广阔的镜头。它的焦距长度短于所用菲林格式的对角线长度。
Wide-Angle lens: lens with wide covering power. It has a focal length which is less than the diagonal of the film format with which it is being used.
这在任何光圈和焦距上都适用，只不过光圈越小、焦距越短，景深越大，你能够拍摄的清晰长度就越大。
This works for all apertures and focal lengths, but the smaller the aperture and the shorter the focal length, and the greater the distance you shoot at, the greater the depth of field.
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