fish

Do you know if the case for 5DmkII is of later fabric (4 clips inestead of 2) or earlier fabric ?

They now come with the 4 clips. I had a 2 clip version but was offered a deal on the upgrade. I have not had any problems with mine at water level or in shallow depths.

Mark, I have the same set up as you. That is the 5D mk II and the 17-40mm as well as the fish eye. I find that the corner sharpness is much better the 15mm. The fish eye allows you as well to focus a lot closer to your subject, but I find the focus noticeably slower than on the 17-40mm.

I don't have any experience with the Tokina...

Below are a couple of photos where you can see the corner blur of the 17-40mm (the photo above) and then a picture taken on a second dive with the 15mm showing more sharpness.

Thanks Bill.
My current set up is a 15mm fish eye and a 9" dome. I have been trying to take a split level photos at water level in moving water. My 9" dome works fine for this purpose in completely still water, but in rivers etc this is quite difficult. I'm note sure about how large is enough so I would appreciate any thoughts and/or experience on this.

As the sole purpose of the dome would be to take photos at the surface I imagine that it would not have to be as robust. Having a large dome in moving water might though open up new problems such as lack of pressure to keep the port tight... Anyway I thought this might be challenging project and found it likely that this had been done by many!