When I first purchased a Canon EF 70-200 f/4L and later upgraded to a Canon EF 70-200 f/4L IS, it was immediately apparent that the picture was not merely "slowing down," but rather, becoming almost motionless. I am not the first person to describe this glass as a "masterpiece of optical engineering." Moreover, the stub is essentially silent (in contrast to the Canon EF 70-200 f/4L IS), which is no longer an issue.