5D Mark III - what is power focusing

[mikey50]

hi. i saw this on the Notes on page 227 of the owner's manual:

"When using a (super) telephoto lens equipped with the power focus mode marketed since the second half of 2011, power focusing is possible during movie shooting."

Can anyone explain power focusing and what telephoto lens has it? thank you.

 

[marvinhello]

telephoto lens: lens that has very long focal length, 100mm, 200mm 300mm etc

Power focusing: allows smooth manual focusing by controlling the lens motor instead of manually twisting the focus ring.
http://cpn.canon-europe.com/content/education/infobank/autofocus/power_focus.do