Archived posting to the Leica Users Group, 1997/02/19
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Good Day! Since PJW took all that time to measure 12 of his lenses-- I figured I would take the time to do calculations in order to prove hime wrong. What actually happened is that I proved him RIGHT. Our system of numerical apertures IS calculated by dividing the focal length by the physical aperture. I still think that measuring the diaphragm by the way it looks is just a coincidence-- otherwise all those lens designers using apertometers all of these years will commit suicide when they find out all they really needed was a good starrett. Hey-- If all you need to do is measure by the apparent opening in the diaphragm I could put a Proxar close-up lens on my 50f1.5 Sonnar and I'll have a f1.1 for my Contax -heh heh heh . Honestly, Peter, you have my apologies, I was wrong-- beat me flog me kill me dead. Dr. Abbe's aperture system of calculating numerical aperture must be an antuquated system -- I've rechecked what the catalogues said, and I did interpret it correctly, although I was always told that we used HIS system today. Oh well, this won't be the last time I'll be wrong. Sincerely, Thomas P. Myro Photology@juno.com