Zen 100mm on Nauticam - corners

The Zen Underwater Fisheye-Macro 100mm Dome Port is one of my new most favorite toys. It's tiny, great for travel, and most importantly works really well with the Tokina 10-17mm fisheye lens. The one knock that is sometimes mentioned on a small dome like this is corner sharpness. While it's not really in my nature to do a lot of test shots, I wanted to see how just how much of an issue it really is with the Zen 100. So, I tossed a snorkel and swim goggles in the water for a subject, jumped in and took a series of shots at 10mm, decreasing in aperture by 1/3 stop from f/3.5 to f/22. Ok, maybe I skipped a stop here or there but, hey, I had to hold my breath.

Zen 100mm on Nauticam NA-7D Zen 100mm on Nauticam NA-7DHere are the shots... first, the full size image, and then a crop of the lower right hand corner (close corners are the problem ones). The end of the snorkel isn't all the way in the corner, but, fortunately this pool is finished with an exposed aggregate so you can see the focus all the way to the corner.

Screen shot 2010-05-07 at 2.41.21 PM

Click here to see the test shots

As you would expect, the corner is soft wide open, i.e. f/3.5, but not as bad as I would have guessed. To my eyes, by F/11 it is sharp, but even by f/7.1 it is pretty good. Overall, I am impressed and pleasantly surprised about this. Given the small size and how close I can get to subjects with it, you can bet you'll see this port on my housing more than any other.