Imagine the idea of a lens that can look behind itself, that’s exactly what a Fisheye-Nikkor 6mm f2.8s can do, delivering a viewing angle of 220-degrees. So what’s this new technology and when did it first arrive? It isn’t new at all actually, the fisheye lens was first introduced at the Photokina trade show in Germany, in the year 1970. This thing is huge, 7-inches long and 10-inches in diameter, wit ha weight over 11 pounds. Imagine trying to comfortably hold this thing while taking a photo.
Few of these were ever produced, and that means that they aren’t exactly cheap to get a hold of. If you happen to have $160,000 just laying around somewhere though, you can own one of the strangest lens ever made in history by purchasing it through the specialty camera shop, Grays of Westminster. Just imagine pairing this with your modern DSLR. Cool concept, though only an extreme collector would ever have the want or means to make such a purchase.
[ source ]