Definitions for "Back Focus"
Keywords:  zoom, focal, infinity, lens, focus
A mechanical adjustment in a camera that moves the imaging device relative to the lens to compensate for different focal lengths of lenses. This is important when a zoom lens is fitted.
Critical adjustment on located at rear of HD telephoto lens to ensure sharp focus.
When the lens is focused at infinity, the distance from the rear surface of the lens to the focal plane is called BACK FOCUS.