Aquatica is proud to introduce a new and long awaited Port Extension Ring with Focusing Knob for Canon EF 17-40mm f/4 Lens especially designed for the Canon EF 17-40mm f/4 zoom lenses. It now sports a knob on its side that connects to the lens focus ring via a gear. This same knob has a retractable mechanism that makes installing and removing the lenses a quick and simple operation. This same knob has a retractable mechanism that makes installing and removing the lenses a quick and simple operation.
Autofocus has always been a useful tool when shooting still photography, not so for when it comes down to video, autofocus in video mode is unacceptably slow and most users who shoot video would prefer to have manual control for critical focusing, required for quality video footage. This new extension includes a manual focusing knob and a matching gear for those two lenses, its as been optimized to be used with our acclaimed 9.25 inch Megadome BK-7 coated mineral glass dome port.
The all aluminum construction benefitted from our latest technology improvements and the state of the art 5 axis machining we now have managed to keep its weight to a minimum without compromising the 300ft/90m depth rating associated with all our products.