You don't seem to have a clue as to how lenses work especially with regard to the diaphram. As you stop down the diameter of the optical path is reduced proportinally. If there are scratches , etc on the ***perimeter*** of the rear element and the lens is stopped down enuff taking the angle of view into account, the "crud" on the perimeter is often COMPLETELY OUT OF THE OPTICAL PATH, I.E. IT IS IRELLAVANT AND HAS ZERO AFFECT ON THE IMAGE FORMED BY THE LENS! JCO
-----Original Message----- From: Rob Studdert [mailto:[EMAIL PROTECTED] Sent: Wednesday, July 28, 2004 7:15 PM To: [EMAIL PROTECTED] Subject: RE: Scratch on rear element On 28 Jul 2004 at 11:58, J. C. O'Connell wrote: > not always true, if the "crud" is on the perimeter, > then stopping down can COMPLETELY ELIMINATE the > visibility of the "crud" because it is no longer > in the optical path. I really don't know how you come up with some of this stuff. Stopping down makes crud MORE visible, if it wasn't in the optical path then it never would have been visible at any stop in-fact it could even remotely aid in flare resistance. I just did a test using my patented stick on synthi-crud and easily confirmed my prior experiences, I can provide the pics if you are that keen. Rob Studdert HURSTVILLE AUSTRALIA Tel +61-2-9554-4110 UTC(GMT) +10 Hours [EMAIL PROTECTED] http://members.ozemail.com.au/~distudio/publications/ Pentax user since 1986, PDMLer since 1998
