I bought a used Canon New FD mount 200mm f2.8 and upon receipt discovered that I am unable to mount it on my F-1. I know that the red plastic nipple on the outside of the mount and the red painted index on the inside are supposed to be aligned for a person to mount the lens onto the camera and lock it in place. With the older FD breechlock lenses it is easy to correct that problem but on the newer lenses I have no idea where to poke or prod to solve the problem.
Just press in on the silver release button on the side, and grab the inner part of the back end of the lens and turn it until the red dots align. It will lock into that position when it gets there.
