Getting wide - the Sigma 8-16

For underwater photographers, the Tokina 10-17mm fisheye zoom lens is about the best thing since sliced bread. It's extremely versatile, super wide, and its close focus allows for dramatic close-focus-wide-angle shooting. If I could only have one lens for underwater, it would be the 10-17. Sometimes, though, I don't want that fisheye perspective, and want a super-wide rectilinear lens. When shooting people or sharks, for example, I just don't like what the fisheye perspective does to them. You can reduce the fisheye distortion in post processing, but that isn't very satisfying and loses some image data.

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Shot with Sigma 8-16mm at 8mm Shot with Sigma 8-16mm at 8mmFor cropped frame cameras like the Canon 7D or the Nikon D300s, the typical rectilinear wide angle zoom lenses people use underwater are the Canon 10-22, Nikon 12-24, Nikon 10-24 or 12-24, Tokina 11-16 or Sigma 10-20.

Shot with Sigma 8-16mm at 13mm Shot with Sigma 8-16mm at 13mmAnd then there is the new Sigma 8-16mm F4.5-5.6 DC HSM Ultra Wide Zoom Lens. This is a wide lens, with a diagonal FOV (field of view) at 8mm of about 121º. For comparison, the Canon 10-22 FOV is 107º at 10mm. (Note, though, that the Tokina 10-17 diagonal FOV at 10mm is nearly a 180º fisheye view).

Shot with Sigma 8-16mm at 8mm Shot with Sigma 8-16mm at 8mmWe got a hold of one of these lenses, so naturally I volunteered to jump into the water with it. I outfitted it to my Canon 7D, in a Nauticam NA-7D housing, and brought along 3 different sizes of extension rings. The dome I chose was the Zen Underwater 230mm superdome. Corner sharpness is certainly something to be considered with this wide lens, and the big 230mm dome is my best choice for getting decent corners. After trying the various Nauticam Locking Extension rings, I settled on the 60mm ring as being the best choice; no vignetting seen with this extension at any zoom setting, and corner sharpness turned out to be good. Quick Nauticam plug here - even with this big dome on, I felt confident jumping off of the boat holding this rig thanks to the Nauticam locking port system.

Shot with Sigma 8-16mm at 8mm Shot with Sigma 8-16mm at 8mmThe Zen 230mm dome makes over/under shots much easier than with a smaller dome. The 8-16mm was a good lens choice for this shot taken at the Dry Tortugas - note how it keeps the lines of the old coaling dock straight. I think the 8-16mm lens and the Zen 230mm dome make a terrific combination for over/under shooting.

Shot with Sigma 8-16mm at 8mm Shot with Sigma 8-16mm at 8mm
While I'm no lens tester, I did take the setup in the pool to get a couple of test shots. My limited testing indicated that with the Zen 230mm dome, corner sharpness was good to about f/7.1. I did notice some transverse chromatic aberration around the edges at all apertures. You can also see from this shot the relative lack of distortion, and that the straight lines look like straight lines.

Corner crop of above image Corner crop of above image