Fisheye vs Focal length

[timmyquest]

If you have a 12mm lens and a 12mm fisheye lens, will the fisheye offer a "wider" image.

I'm aware of the visual effects of the fisheye, but does it allow you to see more as well?

[eric1]

hmm. my friend has a 12mm fish. it's supposed to provide a 180 deg. field of view. i would imagine a (renticular?) lens would have the same FOV, but need to be be bigger to accomadate this. i'm sure someone hear has the right answer if i'm wrong.