Originally posted by JimJohnson It's really fast and easy. Move the switch on the lower left side of the mirror box to the MF position.
Partly I'm posting to be educated. Why would you want to disable SDM driven AF?
Some times the SDM motor completely fails, which leaves a dead lens, converting to screw drive means you can still use the lens.
Other times like my 50-135 SDM, it would take 3-6 mins to start focusing (which is a lifetime in the middle of a photoshoot), and I was tired of the song and dance I had to do to get it to awaken.
Finally, some people felt that screw drive is also slightly faster than the SDM focusing.