I have today baught a Sinar Norma outfit with a Schneider symmar 150 / 265 lens. Can you tell me if my assumption that removeing the rear elements converts it from 150 to 265 is correct. I have never come across this type of lens before and would be interested to hear peoples oppinion of it.
6 hours and only one mistake - that's really good!
BTW the 150mm symmar is a pretty good 150mm lens; as a 265 it is prone to chromatic aberration in the corners of 4x5". It will be sharper than enlarging the central part of a 4x5" negative 1.77 times extra, but not as sharp as a negative shot with a "real" 265mm lens. The center of a negative shot with a converted Symmar is pretty good, so if you need to crop/enlarge even more it can be really useful.
In other words I will only recommend the converted lens if that's the only way to get the shot. Or if you want fuzzy corners.
I've found that my 210/370 converts with either the front OR the back, though it seems a little sharper with the back on, I can actually use it on my 4x5 with the front on since it moves the nodal point further forward.
I haven't used this exact lens, but I do have a convertable (?14-19-26?) Wollensak that I still use on my 11x14. It was my first (and at that time only) 11x14 lens, so I used it in single cel mode often. What hasn't been mentioned is filters. If you are shooting B&W, then adding a yellow or orange filter to the single cel will significantly improve the apparent resolution. Great trick for B&W, looks "rather odd" with color film ;-)
(there was a url link here which no longer exists) was shot with a converted Symmar 150mm, and (there was a url link here which no longer exists) is an enlargement of the top right corner showing chromatic aberration (and quite a bit of astigmatism, too).