 It is equal to the distance between the image plane and a pinhole that images distant objects the same size as the lens in question.For rectilinear lenses (that is, with no image distortion), the imaging of distant objects is well modelled as a pinhole camera model.This model leads to the simple geometric model that photographers use for computing the angle of view of a camera; in this case, the angle of view depends only on the ratio of focal length to film size.