In this 9th Tale, I introduce an ultra wideangle SLR lens for F mount, "Nikkor 13 mm f/5.6" that has the world's widest angle of field (2 omega = 118 degrees) among ultra wideangle lenses of the ordinary projection system for 35 mm (135) format SLR cameras.
This record is not yet renewed even at this moment of 21st century.
Now we follow the changes of 13 mm f/5.6.
Nikkor 13 mm f/5.6 was released (on order basis) in March 1976. It appeared one of so-called "new Nikkor", the lens with the new outlook design, multi-layer coating and automatic stop.
I've heard that it won highest praise as "it has extra wide angle of field, and that, excellent performance", since it can obtain very sharp focus over the entire shooting distance from the infinity to the closest 0.3 m due to the adoption of "collection of close distance aberration (Nikon-special floating system) ".
Then modification of the AI coupled exposure system (automatic correction from fully-open f-stop) was applied to this "Nikkor 13 mm f/5.6" and it appeared again as "AI Nikkor 13 mm f/5.6" in June 1977.
Further in March 1982, it was changed to "AI Nikkor 13 mm f/5.6S". After that, the basic design was not changed until it was discontinued and it had been selling long, for more than 20 years.
The optical system of "Nikkor 13 mm f/5.6" was designed by Mr. MORI, Ikuo of 1st Optical Section, Optical Designing Department (then).
Mr. Mori was the right-hand man of Mr. WAKIMOTO, introduced in Tale One. The lenses designed by Mr. MORI varies from ultra wideangle Nikkors for F mount, PC Nikkors, Nikkors for Bronica, Nikkors for large format cameras to EL Nikkors for enlarging.
I have been working with him till a recent date. He was a frank and gentle person. We were always astonished at his knowledge and insight of lens designing. I introduce some of the anecdotes about his design handed down to this date.
One is a story of when he renewed the old "EL Nikkor 50 mm f/2.8" (designed by Mr. WAKIMOTO). The wizard lens designer Mr. WAKIMOTO said, "I take off my hat to Mr. MORI!" as Mr. MORI made the renewal design perfectly well.
Of course, the old "EL Nikkor 50 mm f/2.8" was an excellent lens and Mr. WAKIMOTO invented this WAKIMOTO type (EL-Nikkor type) lens with the hard work.
Mr. WAKIMOTO had no other word than "God, it's a knockout!" to Mr. MORI who made it much better than expected, though it was made at a later time when everything was advancing than before.
Another story. Mr. SHIMIZU, the originator of Nikkor Auto who was introduced in Tale 5 mentioned in retrospect, "I thought it's impossible to design that ultra wideangle 13 mm. Mr. MORI was a super designer."
Mr. MORI full of such anecdotes retired a few years ago at the retirement age.
Japanese master designers are seldom known to the public, but their course of the work can be followed via their reports, log of development, notes, patents, and so on.
It tends to be thought that "13 mm f/5.6" was designed in order to make the angle of field of "Auto NIKKOR 15 mm f/5.6" (1973) or "NIKKOR 18 mm f/4" (1975) wider, but it is not true.
Mr. MORI started to design ultra wideangle lenses with various specifications in parallel before 1970, with setting such conditions as focal lengths of 13 mm, 15 mm and 18 mm, and apertures of f/3.5 ~ f/8. In his reports of those days, original types of each lens were shown (to our surprise, he was even studying the lens with an aspherical lens).
Out of them, "15 mm f/5.6", "18 mm f/4" and "13 mm f/5.6", in that order, were selected for production models, after a few times of prototyping.
Now, let's follow his history of development of "13 mm" more in detail.
First, he proceeded the development with specifications of "13 mm f/8", finished the design in 1971 and issued the blueprint in March of the same year. Details after that is not known, but "13 mm f/8" was never produced.
The design was further improved and faster "13 mm f/5.6" was prototyped in 1973 and it was released (on order basis) in March 1976.
Mr. MORI applied the patent for the invention of this ultra wideangle lens to U.S. Patent Office in 1971 and was granted the U.S.P. (patent) in 1973. This ultra wideangle lens was judged as an invention of a new type lens.
That was the time when a large scale computer was introduced to the lens designing, but its performance was much inferior than that of a current personal computer.
It took too much time and the simulation was not sufficiently made. His contribution to Nikkor lenses was immeasurably great.