Is using a follow focus on the HPX171 stock lens any useful? I know it is not ideal because the focus ring is spinning, but as long as I don't reach the limits (infinte focus and close focus) for example using hard stops on a follow focus, there shouldn't be any problem, or not? I've read that the change in focus differs if you turn the focussing ring faster or slower. If that's true, that would mean no repeatable results are possible and therefore that a follow focuse would be quite useless. Then again: there are purposely built follow focus gears for the HPX, so that would imply that it a follow focus IS useful...