This focus gear enables manual focus adjustment for the Canon EF 8-15mm f/4L Fisheye USM lens via the housing's focus/zoom knob when used with Sea&Sea dSLR housings.
The focus gear is useful in the following situations:
* When you need to manually adjust focus as your subject is not situated within the AF frame or in order to maximize the effect of the lens’s minimal shooting distance of 15cm/5.9 inches.
* 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 cannot be used in conjunction with the zoom gear (product #31154). Only one lens gear can be used at a time.
