Autofocus

[Benoît-Joan Clariana-Roig]

The sports L lenses in particular are designed to work well - quickly and silently - with focusing on a continually moving subject. All the intelligence is in the camera.

I'm pretty sure that the sport lenses RD was used to do the RD of the latest video lenses.

[Paul Russell]

Highly likely. And those lenses, even as low as the 70-200mm L IS are quite happy moving swiftly, silently and gradually as the camera commands.

[Brian Iannone]

Thank you everyone for the replies. :)