Jack Douglas said:
Thanks very much Go Wild; I love enthusiasm!

I'm working my butt off to learn the 1DX II in spite of my 6D handicap.
East W I sure hope you are wrong since that would seem a big blunder by Canon.
Jack
Oh dear how do I tell my wife I need to spend more money!
In control systems a servo feedback control system can handle speed variation and that's what I assumed, that there were measurement and feedback parameters that made it controllable. I know a stepper motor is a whole different beast.
Jack
Not a blunder, just what the STM motor was designed for. Prior to these new camera models, the focus speed setting was not prevalent. Photogs were wanting faster and faster af speeds....then folks complained it was too fast for video and wanted better control.
Again, canon wants you to buy the equipment for your needs....and of course extra equipment for each.