Hasselblad / Zeiss Distagon CFi 30mm f/3.5 (Fisheye)

Bend the whole 6x6 frame into a wall of curved horizon and you are using the lens it was built to be. This is Hasselblad's full-frame fisheye, the only one the V system ever put into regular production, and it fills the square negative corner to corner rather than dropping a circular image inside black borders. You get roughly 180 degrees across the diagonal, and any straight line off the center axis curves hard. There was one other fisheye in the system, the Carl Zeiss 24mm F-Distagon IHI, a true circular fisheye built in tiny numbers for technical work. Almost nobody will ever see one. For practical purposes the 30mm is the fisheye a Hasselblad shooter can actually buy.

The design is the Zeiss F-Distagon, the fisheye member of the Distagon retrofocus family, and the F is the part that matters: it marks this as the curved-projection lens rather than the rectilinear Distagon line that includes the 40mm. Retrofocus is what lets a 30mm sit far enough back to clear the V system's mirror. Wide open at f/3.5 the center is already crisp, and stopping down to f/8 or f/11 pulls the extreme edges into line. Flare control is better than you would expect from a front element this bulbous, but shoot straight into a hard sun and that curved glass will still throw the occasional ghost. Color and contrast hold up against the rest of the CFi line, which is the practical bar here, not vague Zeiss reputation.

You cannot screw a normal filter onto the front because the element bulges too far out, so the filters live behind the front group. The documented set is a neutral compensation glass plus yellow, orange, and blue, in 26mm threads that mount on the rear of that front component. To change one you unscrew and remove the front group, swap the filter, and rebuild. There is no turret to dial; it is a physical swap on the bench or in the field. One glass always has to be in place, because it is part of the optical formula, so even shooting clear you leave the neutral element loaded.

Inside the barrel sits a Prontor CF leaf shutter, the same shutter every CF and CFi V lens carries (the Prontor arrived with the CF generation, replacing the older Synchro-Compur of the C-series glass, and the CFi carries a further-refined, longer-life version of it). Flash syncs at every speed up to 1/500, which is exactly why a leaf-shutter fisheye exists. The people who reach for one are shooting architecture, interiors, and the occasional surreal landscape, often balancing a flash against ambient window light. In Zone Light Meter, meter the ambient at your chosen aperture and let the leaf-shutter sync carry the fill, no focal-plane speed ceiling like the one that kills this trick on 35mm bodies.

The limitation is permanent and severe distortion. There is no setting that turns this into a rectilinear ultra-wide; if you want straight walls on 6x6 you reach for the 40mm Distagon, which is the lens most buyers cross-shop. The 30mm sits idle between the jobs that actually demand it. Today it trades for serious money, partly because so few were made and partly because nothing else in the system does what it does. The CFi is the version to find, with the improved coatings and the better screen compatibility over the earlier CF.