I have a Tamron SP 500mm 1:8 55BB lens with a Pentax KM adaptall, it locks in place nicely on the mirror lens but I also have a Tamron SP BBAR MC 2x Converter, which is also adaptall but when I put the KM on the converter it lines up and goes on great but it doesnt lock in place, nothing looks broken......
if anyone can shed some light on this please help!
also there is a ring with a red screw on the Tamron 500mm anyone know what thats for?
I attached some pictures for visuals
Tamron 2x converter
mirror lens with KM attached, screw to the left of the green dot
adaptall km
adaptall km