|Posted: Sun Sep 17, 2023 11:12 am Post subject:
|As Alun alluded to, separating the doublet may be the bigger challenge.
If the doublet has been cemented with Canada balsam, then gently, slowly warming it to about 300˚F / 150˚C should allow them to slide apart. I have had success with that on an older Minolta Rokkor lens.
I have a Bronica PS doublet with a hazed epoxy cement layer; soaking the doublet in acetone did nothing, methylene chloride is unobtainable here, the final option to try (according to Norland) is to gently heat the doublet up to 400˚F, and hold it there for an hour, upon which the epoxy should lose its adherence. I haven't had the courage yet to do that.
As far as cementing is concerned; a UV-curing optical cement can be used, or Canada balsam. I have had partial success with a UV-curing cement, but that was a generic one; optical grade UV-curing cements are difficult to source here, are very expensive, and have no shelf-life to speak of.
I do have a Canada balsam-in-xylene solution prepared for cementing; that requires a few weeks of edge-hardening before it can be handled.
Pure Canada balsam (not in hardened stick-form) can also be used, which can be made up of different hardnesses depending on how much of the natural turpentines you boil off before you use it. This type of Canada balsam cement needs to be applied hot, which isn't an easy task. Smaller lenses can use a harder balsam, larger lenses need a softer balsam.
Mounting the lenses with an air-gap is problematic if they were designed for cementing; you will need a very thin separator otherwise you will end up with Newton-rings. Oil-mounting would be another alternative, but I have no experience with that myself.
SONY A7S, A7RII + dust-sealed modded Novoflex/Fotodiox/Rayqual MD-NEX adapters
Minolta SR-1, SRT-101/303, XD7/XD11, XGM, X700
Minolta majority of all Rokkor SR/AR/MC/MD models made
Sigma 14mm/3.5 for SR mount
Tamron SP 60B 300mm/2.8 (Adaptall)
Samyang T-S 24mm/3.5 (Nikon mount, DIY converted to SR mount)
Schneider-Kreuznach PC-Super-Angulon 28mm/2.8 (SR mount)
Bronica PS 35/40/50/65/80/110/135/150/180/200/250mm