Originally posted by FGolesic adapting inherited pentax macro lenses to my canon rebel , love them , but cannot control aperature . trimmed tab , but that does not help . The aperature seems to want to change , but hand pressure on the tab is needed .
Sorry you opted to trim the tab. That is often done to avoid mirror clearance issues with FF Canon models, but is not a problem for adapting. Your problem sounds strange to me in that K-mount lenses having aperture rings are stopped down as their default condition when not mounted to a camera. Unless your adapter features aperture ring emulation or similar, there is no reason for the lens to be wide open unless it is has a fault internally.
Steve