On 02/09/07, P. J. Alling <[EMAIL PROTECTED]> wrote: > Unfortunately you can't vary the input for focal length in your > formulas, which is the whole point to comparing different AOVs of > particular focal lengths on different formats. It's complicated by the > fact that different nominal focal lengths in fisheye lenses give > equivalent results. Just in Pentax we have 3 full frame 35mm format > fisheye lenses with different focal lengths, (M42 Takumar 18mm f11, > [K]17mm f4.0 A 16mm f2.8, not to mention the fisheye zooms), each > delivering ~180º diagonally, and ~110º horizontally. The image mapping > is anything but linear, which makes AOV calculations for different > formats approximate at best. However based on experimentation and known > lens focal lengths You can compare lens coverages on other formats, (but > not AOV). For example, a 17mm lens is the equivalent of a 35mm lens on > 6x7 and behold Pentax made a 17mm fisheye for 35mm and a 35mm fisheye > for 6x7, 16mm on 35mm is the equivalent of a 10mm lens on the Pentax > APS-C sensor digitals, and loh Pentax makes a 10-17mm fisheye zoom for > APS-C.
Indeed, I left out a crucial parameter in that it was is relevant only for a fisheye lens that produced 180degrees diagonal coverage on a full frame. I pulled it out of my pano spread sheet where it worked a charm. -- Rob Studdert HURSTVILLE AUSTRALIA Tel +61-2-9554-4110 UTC(GMT) +10 Hours [EMAIL PROTECTED] http://picasaweb.google.com/distudio/PESO http://home.swiftdsl.com.au/~distudio//publications/ Pentax user since 1986, PDMLer since 1998 -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net
