I am getting a 39mm Leica screw mount close-up lens (an "obsolete" APO close-up lens according to the Rodenstock website, Rodagon R 75mm f4 lens) to use in stop-down metering mode on my
FM3a (I hope I do not have to change the focusing screen). My old adapter is non-AI F mount which like non-AI lenses (if I understand correctly) will damage the FM3 mount. Can the old F mount adapter connect to an AI extension tube - Is there a Nikon or aftermarket focusing device for AI/AIS mount cameras? Tom