Guy Glorieux <guy.glorieux@sympatico.ca> writes: > Hmmm... Bob, Yes, Bob is just teasing, because so many people think that a "focal length" defines the angle of view, by conversion to 35mm format. > Hence, while any pinhole will always create an image, irrespective of > the focal length, there corresponds only a single "optimal" pinhole > diameter for any single focal length. Check Larry Fratkin's excellent > "Pinhole Camera Design Calculator" on this subject > http://www.mrpinhole.com/calcpinh.php Hmm. His explanation includes the statement: "This is due to a trade off between flare and fuzziness." I think by "flare" he means "diffraction" (obviously he does, or the wavelength wouldn't be involved). (Very clunky, if you ask me, using php to involve a trip to the server for each calculation.) > Of course, any object in front of an optimal pinhole will always be in > focus on the film plane (as long as the object-to-pinhole distance is > greater than the pinhole-to-film distance). Huh? You mean as you move the subject closer and closer, there comes a sudden point (when v = u) when the light rays get confused, and stop travelling in straight lines? No, I think your condition in parenthesis is just wrong. Of course, if the image is large than the subject it's likely to be *very* faint. Brian Chandler ---------------- geo://Sano.Japan.Planet_3 Jigsaw puzzles from Japan at: http://imaginatorium.org/shop/
