Nikkor-P·C 10.5cm f/2.5

Zenji Wakimoto (脇本善司) computed the optics for the 10.5cm f/2.5 in 1949, but the lens took the slow road to market: production drawings were only finalized in the spring of 1953, and sources split on the launch — December 1953 per the Japanese Wikipedia, late summer 1954 in Nikon’s own account. It arrived to fill the awkward gap between the 8.5cm and 13.5cm Nikkors, and its slightly odd f/2.5 aperture was no accident: in an era when Nikon counted every fraction of a stop against its rivals, f/2.5 made this the fastest lens in the 100mm class at the time. The design is a classic Sonnar — five elements in three groups, with a thick cemented triplet buried in the rear — and Wakimoto made one deliberately “wrong” choice that defined its character: he left the spherical aberration slightly under-corrected, trading a hair of clinical bite for background blur that reviewers still reach for words like “exquisite” to describe.

The gamble paid off. The 10.5cm became a best-seller — by Nikon’s own account it split the era’s popularity evenly with the celebrated 8.5cm f/2 — favored by Ken Domon (土門拳) among other photographers, with production around 22,000 units (Rotoloni, via 35mmc) making it the volume telephoto of the S system. Today it sits in the shadow of the more glamorous 8.5cm f/2, and because it was made in such numbers, clean examples remain the affordable entry into Nikon rangefinder telephotos. A Leica screw-mount version followed around 1956, differing only in its mount; Richard Haw notes the barrel itself evolved once, from early examples with two small hood-securing lugs to a later smooth-fronted version, and that the lens only ever wore the “new” chrome-and-black panda scheme — it arrived too late for the all-chrome dress of the older teles.

Its real legacy, though, is longevity. When Nikon pivoted to the SLR, Wakimoto’s computation crossed over almost intact — the rear element was shaved by roughly a millimeter to clear the Nikon F’s mirror (Haw; Nikon’s essay cites the same 1.0mm reduction), and that was essentially that. The same 1949 Sonnar soldiered on in the F-mount 105mm f/2.5 until 1971, a run of about 17 years, when Yoshiyuki Shimizu’s (清水義之) Xenotar-type (Gauss-derived) redesign — drawn up in the winter of 1966 — finally replaced it from serial 407301. Few lens designs of any era can claim their optical formula outlived the camera system it was born into.