How can nikkor 6mm f/2.8 see behind itself?: Open Talk Forum: Digital Photography Review
Lens pr0n: The Nikkor 6mm f/2.8 fisheye monster | TechCrunch
Lensfinder.com - Ultra Rare Nikkor 6mm f/5.6. Only a few hundred of these lenses exist. This lens has a 220 degree field of view for Full Frame 24x36mm sensors. Made in Japan
Nikon's 6mm f/2.8 Fisheye on a Z 9 - first time ever? - YouTube