Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.
Benefits of registering include
At the time I tested the Panasonic 8mm fisheye and the Olympus 12mm I only had the 4.33 inch dome port. I expect the 12 mm would also work with the smaller 3.5 inch dome port which has now been discontinued I think. While I did not shoot the 12mm F/2 at F/2 you need to keep in mind that AF works off of the widest F/stop so all things being equal an F/2 lens should focus faster than say an F/4 lens regardless of the F/stop being used at the time you lock focus. I think the 12mm is an outstanding U/W lens and should be added to the Nauticam list of lens choices for M43 cameras. I am now using the Olympus E-M5 out of water and hope to see a housing for this camera come to the market soon.