> Subject: RE: Mamiya fisheye > > > On 10 Mar 2003 at 7:23, Mishka wrote: > > > fisheye with no distortion is no more oxymoron than rectilinear with no > > distortion. > > it is not possible to map 3d world as we see it (hemisphere) on > a plane with no > > distortion. from this point of view, rectilinear is as bad as > fisheye, just > > different. when speaking of lenses, "no distortion" usually > means "no deviation > > from the idealized mapping", for rectilinear being > x=t*tan(theta), and for > > fisheye x=r*theta or x=r*sin(theta).
A rectilinear lens has a constant focal length vs. off axis angle and renders a natural looking reproduction as long as the viewing angle of view matches the taking angle of view. A fisheye on the other hand, has a non linear focal length vs. off axis angle. It's longer in the center of the view and very short at the off axis edges. This transformation causes a very obvious distortion of reality. But that what makes them fun! JCO
