I was given a Tamron 70-210mm zoom lens by my son-in-law, who got it for free. It has a Pentax K mount adapter, and I own Nikon Fs. I need an adaptor which will allow the diaphragm to be held open until the exposure is made (a la the standard Auto-Nikkor lenses). The lens itself seems to have the standard auto-diaphragm pin protruding from the back. I have had a preliminary look on eBay, but I'm not sure which Tamron adaptor I require. I don't need any electronic coupling, or any meter coupling at all, as my Fs have the plain, non-metered prisms. One auction stated: ..."Noelectronic or manual linkage. Allows lenses to be used in stop down Manual focusmode only." Should I be looking for an Adaptall 2 adaptor, or anything which is suitable for the AI lenses? Any input on this would be appreciated; I don't want to buy an adaptor which will allow the lens to work only in a manual diaphragm mode.