Nikkor-O 2.1cm f/4

When Nikon began telling the stories of its own lenses in the long-running “NIKKOR — The Thousand and One Nights” essay series, it chose this one to open with: installment No.1 is the Nikkor-O 2.1cm f/4. Announced in both mounts together at the June 1959 IPEX show, it was the widest lens ever offered for the Nikon rangefinder system — and, in its mirror-up F-mount form, the widest Japanese lens for SLR photography at its debut. Designer Zenji Wakimoto (脇本善司, 1924–1996) gave it a fully symmetrical eight-element, four-group construction that Nikon calls the “Wakimoto type”; Japanese Wikipedia instead files it as a Rusinov type, designed around Bertele’s Biogon patent — the essay itself takes care to distinguish it from the Biogon’s structure.

The design’s refusal of the retrofocus compromise is the whole story. Nikon’s essay — written by Haruo Sato (佐藤治夫) — locates the invention in the two cemented three-element groups flanking the aperture, and the price of that symmetry is a rear group reaching to within about 7mm of the film plane. On the Nikon F that meant locking the mirror up, focusing by the distance scale, and framing through an external finder riding the camera’s accessory shoe; the finder also mounts on a shoe molded into the lens’s deep rear cap, a detail collectors still check for. Sato’s essay also preserves a memorable portrait of the designer: Wakimoto was known for dangling his legs off the edge of the unfenced Ohi plant roof — and later walking along it — antics that reportedly prompted the installation of safety fencing.

The two mounts had opposite fates. The S-mount version, serials 621001 up, arrived just as the F was ending the rangefinder era: serial dating brackets its run at May 1959 to June 1960, and the confirmed span reaches only 621330 (one reported example runs as high as 621526). How many were made is genuinely unsettled, and the estimates are worth keeping side by side: 298 per a claimed factory-records figure on gigantoptik.com — a single hobby site, which itself notes ~330 examples reported from serial listings — against roughly 300 per Mikio Kuno (久野幹雄), ~330 by the serial span, and up to ~600 per NHS and Pacific Rim Camera estimates. The F-mount version, on sale from December 1959, ran nearly a decade to September 1967 across prototypes, a first series, and a late Nikkormat-fit mount revision — roughly 5,956 by serial-span arithmetic (a 7,163 figure also circulates), plus about 1,600 separately serialized finders. Per Rotoloni and the NHS, the two are optically identical except for a small modification to the rear element.

That near-identity is what makes the family the poster child for the undervalued sibling: S-mount examples trade at $3,000–6,000 while the same glass in F mount changes hands for under $500. Reviewers past and present land in roughly the same place — simple, honest distortion and real sharpness stopped down, genuine charm on film, real hazards anywhere near a digital sensor — and the cheap version delivers all of it. The expensive one delivers something else: the final, widest statement of the Nikon rangefinder system, made in its last year of life.