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Good Evening (UK time!)
I still have a pretty old (one of the early generations!) Flektagon which I bought 2nd hand in the early 80s for use on my Edixa and Praktica M42 bodies - and it was very useful, not least because it focuses very close (0.18m) and was pretty sharp.
It is an auto-diaphragm version with the usual pin on the rear face which is operated by the "push bar" in the camera body - but it has a rather unusual (to me at least ) preview mechanism, consisting of a flat spring-loaded pin on the lens body which you press to close the diaphragm for preview purposes, and that works find on the film bodies.However, of course, Pentax DSLRs don' have that push bar, and so the diaphragm is always open unless you push it down externally to take a shot - which is inconvenient to say the least.
I use a generic M42-PK adapter to mate the lens to the bodies but that still allows the spring-loaded pin to stay out, not depressed -
so does anyone know a way of holding that pin "permanently" depressed so that i can use it as a pre-set lens, but without gluing it down or opening the lens to disconnect something or other? . The latter would not seem very easy anyway because the rear mount has no visible securing screws, and I think, the central part is screwed into the surrounding mount - and it looks pretty tight. Anyway I don't need to take the lens apart to clean out fungus or dust, because there is not much of that, although I think the focusing ring could use some TLC as it is pretty tight, and I would get a lens repairer to do that if the aperture operation issue can be solved.
Thanks in advance.
John
PS: the only solution I can think of at the moment is to sandwich "something" between the lens mount and the M-42-PK adapter to hold the pin down, but not sure what that "something" could be.