This focus gear enables manual focus adjustment for the Canon EF 16-35mm f/2.8L II USM lens via the Athena Extension Ring 60 with Focus Knob when used with Sea&Sea MDX-series or Nauticam dSLR housings.
The focus gear is useful in the following situations:
* When you shoot fast moving subjects, like dolphins under limited ambient light (dark environment), so auto focus does not function effectively.
* When you shoot “half-in half-out” photos and would like to manually adjust focus on subjects on land and underwater.
* The focus gear can be used in conjunction with the zoom gear (for Sea&Sea product #31114 / for Nauticam product #19526).
