Nikon's auto-diaphragm circular fisheye — the manual-focus 8mm f/2.8 for the F mount, 180-degree view.
The Fisheye-Nikkor Auto 8mm f/2.8 is a circular fisheye for the Nikon F system, introduced around 1970 as part of the automatic-diaphragm generation. Unlike the earlier mirror-lock-up fisheyes, this design allowed the mirror to operate normally, making it far more practical for handheld use. It projects a full 180-degree circular image inside the 24x36mm frame.
This is a manual-focus Nikon F lens with a maximum aperture of f/2.8 and a fixed 8mm focal length, featuring an automatic diaphragm that stays open for viewing and closes to the set value on exposure. It delivers a 180-degree angle of view as a circular image and carries built-in filters selected by a rotating turret rather than a front-mounted thread. Element counts and weight are omitted to avoid guessing.
The rendering is a classic circular fisheye with pronounced barrel distortion curving all lines away from centre and a dark surround where the image circle does not fill the frame. It suits whole-sky records, interiors, and creative wide work where the round projection is the intended effect. Depth of field is vast, so precise focusing is rarely critical.
On the used market these Auto fisheyes are sought by collectors and by photographers who want the circular look, and prices reflect their scarcity. Check the front element and internal filter turret for haze and smooth operation, confirm the automatic diaphragm snaps closed correctly, and look for fungus in the deep rear group. Mirrorless adaptation is feasible since it does not need mirror lock-up, though the round image remains a specialist result.