Too much math, not enough photography .... I don't understand the need for equations, nor do I understand the math, the equations, or your conclusion.
Like I said, the field of view, regardless of your math, is greater with the Zenitar than it is with a 20mm lens on a 35mm camera. Have you looked through both focal lengths on a 35mm camera? Have you actually compared photos side-by-side? Shel > [Original Message] > From: Cory Papenfuss > Perhaps I wasn't clear enough in my post. I scoured the 'net for > some equations on rectilinear vs. fisheye projections horizontal and > vertical FOV. They're approximate (especially for the fisheye), but are > as follows: > > Rectilinear: FOV = 2 atan (image size/(2*focal length)) > Fisheye: FOV = 4 asin (image size/(4*focal length)) > > Given 35mm film size of 35.8x24.3mm, and the -DS sensor at 23.5x15.7mm, > you get these numbers (in degrees X by Y landscape mode): > > 20mm Rect: 83x63 (35mm), 61x43 (1.5 crop) > 14mm Rect: 104x82 (35mm), 80x59 (1.5 crop) > 16mm Fish: 136x89 (35mm), 86x57 (1.5 crop) > > So, what I *meant* to say is that FOV of the fisheye is about > equivalent to a 13-14mm rectilinear lens on the -DS, or a 20mm rectilinear > lens on a full-frame 35mm body. > > -Cory > > On Sat, 23 Apr 2005, Shel Belinkoff wrote: > > > Huh! > > > > I've used a 16mm Zenitar, an 18mm and 20mm Pentax on a 35mm camera. The > > Zenitar isn't a 20mm ... it's CONSIDERABLY wider than the 20mm and the > > 18mm. How do you arrive at the conclusion that the 16mm Zenitar equates to > > 20mm coverage on 35mm? > > > > Shel > > > >> On Sat, 23 Apr 2005 11:31:44 -0400 (EDT), Cory Papenfuss wrote: > >> > >>> Anyway, the 16mm Zenitar fisheye can be had for $100-$150 and > >>> equates to about 20mm coverage on a 35mm, or 13-14mm > >>> rectilinear on a 1.5 cropped body. > > > > > > > ************************************************************************* > * Cory Papenfuss * > * Electrical Engineering candidate Ph.D. graduate student * > * Virginia Polytechnic Institute and State University * > *************************************************************************
