<<Alex said: As I wrote on your facebook page - for full frame I see this lens as a 8 and 15mm rather than 8 to 15mm for full frame users. A zoom that you either use at one end of the other. For crop sensor work the useful range seems to be 10-15mm - rather like a high quality version of the 10-17mm Tok. If you are a Canon user with both a full frame and crop sensor camera - then you will get many, many options from this lens. Alex>>
Thanks Alex, and you are absolutely correct. On full frame camera I was always racking to one end or the other. The in-betweens were kind of irrelevant. But, on the 60D with 1.6 crop, it was useful throughout the zoom range, similar to the Tokina 10-17 on a cropped sensor camera. I haven't tried it with my MKIV yet, but as this is the only way to get 180-degree fisheye with that 1.3 crop, it is a no-brainer for me to have this lens. Have fun in Canada! I got back into cold water this summer in Alaska after 7-years off drysuits, and I'm hooked again. I know it will be ultra-productive for you and the boys.
<<Stew said: How does this lens compare at the 15mm end with the Canon 15mm and the Sigma 15mm which I already own. Would it be a worthy investment to have it to use as you say Alex at opposite ends. Most of my WA photography is Red Sea reef shots on the 5D MKII, but I also still have my cropped sensored 350D. Stew>>
Stew - Absolutely worthy for 350D. Really an essential lens for any Canon shooter interested in wide-angle using a cropped sensor lens. In the Red Sea it will be fabulous, and very versatile.
<<Paul said: If I remember correctly, this lens has closer focus than Canon's 15mm prime FE. Have you had chance to shoot anything at its closest focus setting?>>

Paul - The shot above was done with the Seacam 60D housing and macro fisheye port almost touching the whale shark's mouth. I didn't have my eye to viewfinder, just swimming along with housing alongside the shark. So, I could see that I was like 4" away from mouth at that point. I was using single-servo AF and it never locked me out on AF, so I don't know how close it will really go. But, with fisheye macro port it will be much closer than conventional Canon or Sigma 15mm.
Speaking of ports and pelagic animals, I had a buddy shooting with a 5DII with Seacam superdome and sunshades. Swimming after whale sharks using that was like pushing a sea anchor. The sunshades provided significant water resistance. I also had my own Seacam for a 5DII, but I removed the sushades so I could use the 8-15mm in circular fisheye. As you know, that's simply unscrewing 3 Allen screws on each port shade, so it takes very little time and no expertise. That provided perceptibly less water resistance than the same housing/port with sunshade.
But, swimming with the Seacam Prelude 60D and the Fisheye Macro port was so effortless. I used the standard pro viewfinder so I could more easily see the LCD for video and to minimize weight, and it was like swimming with a point-and-shoot. Tonga for whales or any free dive scenario, this system rocks.
I just ordered the Fisheye Macro Port without sunshade from Seacam, Then I can use it with 8-15mm on either full frame or cropped cameras, as it is only the port's sunshade that eliminates its functionaity on a full frame camera. The port extension used was 20mm (PVL20), necessary to physically fit the lens with the low profile Fisheye Macro Port, and coincidentally the correct port extension for Superdome.