Re: how does a fisheye lens work?

Dear Harry,

Fisheye lenses, which are different from ordinary wide-angel lenses, work 
according to the "retrofocus" principle, i.e. by suitable combination of 
lens elements the distance between the lens and the 
image plane is made much larger than the focal distance. See the site:

http://www.laurin.com/DataCenter/Dictionary/CD/dr/retrlens.htm

It's something like looking through binoculars in the "wrong" direction.
Best regards
Werner Sieber