Just a slight correction, the tester stated that the tripod mount ring could not be removed on this lens. This is incorrect and of course it can be removed. It is a 3 pin bayonet mount removable from the back of the lens, not a clamp style version as used on earlier lenses. As an owner of this lens since January I can say that this lens is superb at 600mm using f7.1 and f8 for sharpness IMHO. Denis.