Detail Information For using Canon cameras (A-1, AE-1 Program, F-1, FTb and others) with M42 lenses (Praktica, Zenit). M42 lenses are not interchangeable with FD optics, as they have different flange bases. This difference is compensated by the thickness of the adapter, and this fact let M42 lenses work with FD cameras in usual manner. You should remember that the pusher with the fixed ring doesn t work, so diaphragm control of the lens is set manually. This adapter can work with lenses having both only automatic diaphragm (A) and selector A/M (automatic/manual diaphragm). It is possible to use Macro rings and other accessories. Jolos TM Mount Adapter FD/M42 Settings: Put red marks on outer and inner rings of the adapter with red mark on the lens collar together. Turn outer ring clockwise till the end. Set M42 lens. Jolos TM Mount Adapter FD/M42 Removing: Removing of the adapter is made in inverse.