For using Canon cameras (A-1, AE-1 Program, F-1, FTb and others) with Nikon lenses. Nikon 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 Nikon 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.
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 Nikon lens