I guess the Tokina 10-17 is a "must" for wide angle on the 7D? .... Could I use the Canon 15mm fisheye instead? Does fast glass not matter down there like on land? Seems like one would want it wide open as opposed to the Tokina being "slow".
The Tokina is a fabulous WA/Fisheye lens. Take a look at some of the posts about this lens before you take this off of your wish list. It is only available for cropped sensor cameras and you will find full frame folks talking about this lens. I use it behind a 6" dome in an Aquatica housing. I have also seen it used with the zen mini dome with great results. It is a great lens to have for CFWA work.
There is so much information to sort through. And decisions, decisions, decisions. Good luck. Looking forward to seeing pics from your new rig - DiverPam





