W-Nikkor·C 2.8cm f/3.5

The W-Nikkor·C 2.8cm f/3.5 began life as an f/4. Masaki Isshiki (一色真幸) submitted the design report for a symmetrical Orthometar-type wide-angle — six elements in four groups — in January 1952, with production drawings issued the same month; by March 1952 the lens had been reworked to f/3.5, and the f/4 prototypes are believed to have been scrapped. Nikon’s own retrospective suggests the last-minute speed bump was likely competitive pressure — a rival Serenar 2.8cm f/3.5 had appeared exactly a year earlier — and notes that Isshiki’s design carried enough margin in its aberration correction to absorb the extra speed without significant degradation. Released in September 1952, it became the widest lens in the S-mount catalog, a title it held until the 2.5cm f/4 arrived the following year.

Roughly 10,000 were sold, across serial blocks that run 346xxx–349xxx before jumping to 712xxx and beyond. The barrel followed the familiar arc of the early wide Nikkors: heavy chrome-over-brass at first, lightened construction as light-alloy parts came in from July 1956, and eventually a black-barrel facelift — Camera no Naniwa’s figures put the spread at roughly 97 to 142 grams depending on finish. The S-mount version takes 43mm screw-in filters and focuses via the body helicoid; the Leica-thread version, with its own helicoid and infinity lock, takes 34.5mm.

That Leica-screw-mount version is confirmed, but its production count was never published — and unusually, it seems never to have had a run of its own. The known LTM examples amount to three pre-production lenses plus copies interleaved within the early chrome batches (346001–349220); the later 712xxx batches are S-mount only. Per NHS and Rotoloni, only one lens in the system — the 3.5cm f/1.8 — ever received its own LTM serial sequence. And Nikon’s essay concedes the design’s one fault, the very thing nearly every modern reviewer notices first: peripheral illumination ran a little lower than its classmates’, so the pronounced corner darkening that defines the lens’s look today was there from the very start.