http://www.nikonchat.com/nikkor-50mm-1-8-dx/

Should I Canon to Nikon? (Please read!)?
Currently I have a Canon T1i with these lenses, 50mm 1.8 18-55 55-250 mm zoom I wanted to get Canon 15 mm fisheye, but I read that to get the full effect of fish-eye I had a camera with a full frame sensor. I took a look at Nikon and saw with a fisheye to work with all DX cameras. I was thinking of selling all my canon equipment, and get a Nikon D300, the Nikkor 10mm fisheye, 1.8 35mm lens, 300mm zoom-70. Could this be a smart move for me? I love the quality of the D300 and I've always wanted a fisheye. I do a lot of concerts phtography
No bother. For most of the fisheye lens is an expensive gimmick that will grow in about 10 minutes.
Relación entre apertura y luminosidad en un objetivo