Archived posting to the Leica Users Group, 2000/05/19
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]It's my understanding that apocromats are corrected for all three primary colors whereas normal lenses are typically corrected for the two primary colors at the ends of the visual spectrum. This is important with longer lenses where there isn't much depth of focus. It's less important with shorter lenses because they have more depth of focus. The APO Extenders are also corrected for all three primary colors and should be used with APO lenses to maintain their outstanding correction. APO extenders can also be used with non-APO lenses where they will simply be outstanding extenders. It hasn't anything to do with internal focusing. Bud - ----- Original Message ----- From: "Anderson, Ferrel E" <AndersonF@ria.army.mil> To: "'leica users group'" <leica-users@mejac.palo-alto.ca.us> Sent: Friday, May 19, 2000 1:35 PM Subject: [Leica] 100 R Macro (was 60 Macro Elmarit-R) [snip] > > Leica did not recommend the use of any device between the 100 APO lens and > camera body, not even the 2X extender. Since its advent, they do recommend the > use of the APO 2X extender. This leads to another question: Can the APO 2X > extender be used with the same optical performance as the 2x extender on lenses > which do not have internal focusing? Or, conversely, does the 2X extender > result in acceptable performance on the internal focusing APO lenses? My > suspicion is that the APO 2X extender, and the APO 1.4X extender, are designed > for the internal focusing APO lenses, and the 2X extender is designed for the > non APO lenses (except for the 180 APO f3.4 Telyt) which use the bellows effect > for focusing. Anyone know whether this is true? I don't have any of the > extenders, and, therefore, have no practical experience to draw on. > [snip] > > Ferrel Anderson >