Attached Link: http://www.dudak.baka.com/fovcalc.html

Field of View is a technical term that is thrown around alot. The field of view is the width of an area you can see at 1,000 yards. Obviously that has little meaning in a 3d app. To further confuse you, it is a variable that depends on the aperature and distance to the object Focal length: The distance between the film and the optical center of the lens when the lens is focused on infinity. The focal length of the lens on most adjustable cameras is marked in millimetres on the lens mount. Since we don't use real lenses, this is kind of a moot definition too. Focal length is also a variable, depending on the size of the film plain, which we don't use. I'm a professional cameraman and photographer. I've also been using Bryce for close to 6 years. The best I've ever been able to do in Bryce is aproximate whether I am wide, normal or telephoto. In real life I use different format cameras all the time. For example; on a 35mm still camera, a "normal" focal length (ie: 1 to 1 magnification) would be a 50mm lens. On a 16mm movie camera a "normal" focal length is a 25mm lens. As I said, it is a variable number. Since we have no film plain, no lenses, no aperature and no real measurement in actual terms. there is no way to do the calculation; Distance x Image size _______________ = Focal length Object size So, do like I do and use your best judgement. ;-)