Nikkor 8mm Fisheye 

The Fisheye-Nikkor 8mm F/2.8 lens sees and records every object in a full 180 degree hemisphere - everything in front, above, below and to either side of the lens. Unlike other fisheye lenses, it fits the camera without any need to lock up the reflex mirror and takes full advantage of the reflex viewing feature of all Nikon cameras. The focusing range extends down to one foot to permit pinpoint focusing on foreground objects while throwing the background out of focus at large apertures, and the aperture diaphragm couples with the TTL exposure meters for full-aperture exposure measurement. The wide maximum aperture of F/2.8 means that the viewfinder image is extra-bright for easy viewing and focusing even in dim light. A set of five filters is built into the lens barrel.