Photo.net have posted a new article which attempts to clear up the confusion concerning focal length, field of view and digital multipliers and how they relate to each other.

“The field of view of a lens (sometimes called the angle of coverage or angle of view) is defined as the angle (in object space) over which objects are recorded on the film or sensor in a camera. It depends on two factors, the focal length of the lens (see above) and the physical size of the film or sensor. Since it depends on the film/sensor size it’s not a fixed characteristic of a lens and it can only be stated if the size of the film or sensor it will be used with is known. For a lens used to form a rectangular frame, three fields of view are often given; the horizontal FOV, the vertical FOV and the diagonal FOV.”

Website: Photo.net - Field of View - Fisheye and Rectilinear lenses