To tell you the truth, there was no real necessity in fisheye lens as far as photography is my hobby. But I found it interesting to fill up my lens collection with such a lens. All in all, fisheye lenses like this may be useful in architecture or landscape photography. Moreover, they are good at shoting of knives, kukris etc. In other words, I thought that I won't have any difficulties with fisheye lens. So, I decided to purchase this lens and to try it. However, buying became the first problem. The cheapest models – Japanese fisheye lenses made by Sigma – costed about 800$, and all others were about 4000-5000$