Klaus Schroiff , Nov 02, 1999; 02:19 a.m.
It is indeed true that you should use FTM in "One-Shot" mode only because in "AI-servo" the camera would immediately try to counteract your correction in order to find its primary AF target. So the principal steps are (0. use "One Shot"), 1. use AF as a rough focus till it indicates that it has found something, 2. use FTM to fine-tune the setting based on your preferences. You have either to keep the shutter half-pressed or use a custom-function to (de)activate AF via a rear button. I've never heard that FTM can damage the motor - finally there're no mechanical gears with USM. FTM just hasn't much sense DURING AF.