Archived posting to the Leica Users Group, 1996/07/28[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]
In message <9607282118.AA05788@mail.a1.nl>, Willem-Jan Markerink <w.j.markerink@a1.NL> writes >Perhaps my previous subject line wasn't temping enough....;-)) > >Hi gang, > >On the IR list, someone mentioned the fact that Leica, as Nikon, >recommends closing aperture instead of using the IR focus mark. >Assuming that most primes still have such an IR focus mark, this >surprised me. How is this subject treated in Leica manuals? > >[background: one of my technical IR books (written by Guenter >Spitzing, a well known German author of several camera books, I >assume about Leica as well(?)) clearly states that closing down to >minimum aperture is not recommended due to increasing diffraction >with increasing wavelengths (IR being longer waves than visible)] > >Can anyone shed some light on this subject? > Hi W-J, like all the best coincidences, I posted what is, in effect, a rather voluminous answer to this question on the IR group and then found your question here. Leica lenses don't have IR focusing marks nowadays, and I think of the various Leica lenses I've got going back over many years of manuafacture, I can't recall any of them having one. Maybe one does, but I can't remember. To save bandwidth I won't post it here as well unless somebody asks- I'll just leave this as a pointer to it (or does the term "pointer" only refer to web pages....?) -- joe b.