Originally posted by Gregor Thanks for the replies. More specifically, what exactly does the quick shift allow you to do and how do you work around it on a lens that doesn't have it?
quick-shift allows you to adjust the focus after focus has locked or before focus has locked (but you shouldn't try to do it while focusing) without switching the body to MF.
When it is in AF without quickshift, the focus ring is coupled to the body's AF motor, and there is a lot of resistance when you turn it and it can cause damage.
It is good for prefocusing (used for faster focusing on lenses as you focus near what you want to focus) or making minor focus adjustments when the body has chosen a focus that you don't like (ie focused on branches in front of a bird, no AF system can get around that).