what is a fisheye lens?

Answer 1

There are 2 types of "fisheye" lenses. One produces a 360 degree circular image on the film or sensor. The other is a "full frame" with a 180 degree angle of view and extreme "barrel distortion". Vertical lines at the edges are curved; tilt the lens up or down and the horizon becomes curved. Even with the lens perfectly horizontal and centered on the horizon any horizontal lines in the foreground will be curved.

Information tidbit: The "angle of view" of any lens is measured on the diagonal - across the film frame or sensor, not horizontally.

Answer 2

As the others said. It's kind of an extreme wide angle lens which can take a very large area onto a pic but will distort the picture (kind of when you see a reflection on a steel ball). Here are some articles with pictures:

http://www.paullockaby.com/journal/?id=2005/11/03/750143095
http://www.webarts.net/stuff/fisheye/ (in German)
http://www.fotosearch.com/photos-images/fisheye-lens.html
http://www.picture-newsletter.com/fishey/index.htm
http://outdoors.webshots.com/album/559048446kNmebm

Answer 3

It is an extreme wide angle lens that allows a camera to capture a wide field of view and compress it into the camera's frame.

Imagine what you see, in front of you, without turning your head or moving your eyes. This could be your camera's "normal" viewing angle. Everything you see is in the camera's frame.

Now, just turn your eyes to the right and left and up and down. You can see a bit more, but not all at one time. A wide angle lens will compress what you see, from the extreme right and left of your eye's range, and fit it into the camera frame.

You can think of this effect as being the opposite of what a telescope or telephoto lens would do.

Finally, rotate your head all the way to the right and all the way to the left and all the way up and all the way down. You can see even more. A fish eye lens will compress all of THAT into the camera frame.

Answer 4

an ultra wide-angle lens with a 180 degree field of view, resulting in a circular image.

what's interesting is if you're into panoramas, you'll need only 2 pictures taken with a fish-eye lens to make a nifty 360 degree pano -- with the appropriate stitching software.

Answer 5

I special lens that spherizes the image, basically makes everything look like its' inside a clear bubble.