Nikkor 13mm f/5.6

The obvious story about the Nikkor 13mm f/5.6 is that Nikon kept making its ultra-wides wider — 18mm, then 15mm, then 13mm — and the obvious story is wrong. Haruo Sato says so explicitly in Nikon’s own house history: Mori Ikuo had been designing ultra-wide lenses at 13mm, 15mm and 18mm, at apertures from f/3.5 to f/8, in parallel since before 1970. His design reports from those years show an original layout for each, one of them using an aspherical surface. Three of the set were eventually judged worth making, in the order 15mm f/5.6, 18mm f/4, 13mm f/5.6. The widest was not the culmination. It was the one that took longest to become manufacturable.

Mori first finished a 13mm f/8 and issued the drawing in March 1971. That lens was never built. He applied for a United States patent on the ultra-wide type in 1971 and was granted it in 1973 — the office treated it as a new type of lens, not an improvement on an old one — and the same year prototyped the faster f/5.6. Release, on an order-only basis, came in March 1976. Shimizu Yoshiyuki, who had designed the 105mm f/2.5 and the 6mm f/2.8 fisheye, said afterwards that he had thought the 13mm impossible.

What the patent bought is a diagonal field of 118° in which straight lines stay straight. The construction is sixteen elements in twelve groups behind a 115mm front barrel: a negative group ahead of the stop acting as a wide-angle converter that shrinks the image, and a positive master group behind it developed from the triplet and the Tessar. The back focus runs to more than three times the focal length. Sato’s account is blunt about why so much glass is needed — the front groups exist to unwind the master lens’s distortion without wrecking close-range performance, and designing an ultra-wide, he writes, is in a sense a battle with distortion. Close-range correction by floating elements holds the correction down to the 0.3m near limit, which is where an ultra-wide is most often used. The result is a lens with less distortion than many 50mm lenses and, except at the extreme edge, little lateral chromatic aberration.

None of that made it a product. It was built to order for twenty-two years and Roland Vink’s serial blocks account for 36 pre-Ai lenses, 15 Ai lenses and 302 Ai-S lenses — 353 in all, which is where the familiar figure of about 350 comes from. The distribution is the interesting part: five sixths of every 13mm f/5.6 in existence is an Ai-S made after 1982, and the Ai version, on sale from June 1977 to March 1982, is recorded fifteen times. A collector looking for the pre-Ai New Nikkor is looking for one of thirty-six.

Almost everything about the commercial side of the lens is unrecorded. Nikon has published no production figure, so the counts above are arithmetic on serial numbers volunteered by owners. The release date is not settled: Nikon says March 1976, Vink’s serial dating says December 1975, and nothing reconciles them. The only price in general circulation, US$8,229 for 1979, sits in a Wikipedia infobox with no source attached, and no Japanese list price has surfaced at all. Wikipedia also gives 175055 as the first Ai serial — a number that falls inside the pre-Ai block — where Vink gives 175501. For a lens this closely watched, the ledger is remarkably thin.