Summary: I really argued with myself about whether I needed this lens. I was going to visit some National Parks and finally talked myself into it. The photos I took were astonishing. The clarity and depth of focus will take your breath away.
Summary: Closest lens to a fisheye that one can find. Worked flawlessly in extreme conditions - blizzard at the top on Mauna Kea, 14 degrees F and literally 5 hours later we were taking pictures outside of Pahoa of lava flows at in high temp environments. Awesome Lens!