A fisheye lens is a very wide angle lens. It is most common on the 35mm camera. The fisheye lens gets its name from its looks. A big wide lens that protrudes from the camera, it looks like a bulging eye of a fish. A big globe of glass, It generally covers an angle of180 degrees. The lens usually has a focal length of 8mm on a 35mm camera. Nikon even made a 6mm lens which could be ordered directly from Nikon. It covers an angle of over 200 degrees, which ment it could possibly see parcially around your back.
The fisheye lens usually is designed to produce a circular image on the film. There are full frame fisheyes too. Ultra-wide lenses on a 35mm camera of15mm or less have been called fisheyes. Medium format cameras have some full frame fisheye lenses too. For the 4x5 format we used to say 47mm was like a fisheye lens. Lonnie
