NIKKOR - The Thousand and One Nights No.7
NIKKOR-N 5cm F1.1
For the Seventh Tale, I'd like to discuss the NIKKOR-N 5cm f/1.1 interchangeable lens for "S" and "L" (M39 screw) mounts.
by Haruo Sato
The lens was introduced in 1956-02, just the second lens in history faster than f/1.2 (the first was the ZUNOW 5cm f/1.1, released in 1953 by Teikoku Optical Industries, later known as ZUNOW Optical Industries).
Starting around this time, the competition to develop super-fast lenses grew more intense and eventually led to lenses with performance ratings beyond even f/1.0.
It was during this period of energetic research and development that the idea of "lenses faster (brighter) than the human eye" first entered the collective consciousness of photographers around the world.
The optics of the NIKKOR-N 5cm f/1.1 were designed by MURAKAMI, Saburo, who at that time was manager of Nikon's 3rd Mathematics Section, Design Department. MURAKAMI was the right-hand man of AZUMA, Hideo, designer of the W-NIKKOR 3.5cm f/1.8, which was unveiled in September 1956, mentioned in the 3rd Tale.
Though just a handful of Japanese optics designers have attained worldwide renown, the paper trail they left behind -- patents, reports andsuch -- are available to shed more light on their accomplishments.
For example, MURAKAMI filed a patent application for the NIKKOR-N 5cm f/1.1 in 1957; he received a U.S. Patent the following year.
His design was regarded as a new invention, a totally new type of super-fast lens.
MURAKAMI devoted two years of painstaking design work and prototyping to develop the lens.
The designers back then used only an abacus and a sheet of logarithms to conduct ray tracing calculations.
The mind reels at the thought of the incredible volume of calculations and the hours it must have required to arrive at the final design.
Indeed, to succeed during that era, designers needed determination, resilience and, above all, an overriding desire to make better lenses.
I. Lens structure and features
This may come off as a bit technical like the 5th Tale, but bear with me.
First, take a look at the cross-section of the 5cm f/1.1 lens in Fig. 1..
I think it is rather obvious that this is fundamentally a Gaussian (Gauss-type) design.
Like other NIKKOR lenses, the ZUNOW 5cm f/1.1 was an extension of the Sonnar type lens.
The NIKKOR 5cm f/1.1, therefore, differed from its predecessors.
I think most agree it was the correct design decision.
A key design feature of the 5cm f/1.1 lens was the use of a newly developed type of optical glass made with the rare-earth element lanthanum (La) in three (3) convex (positive) lenses.
This provided significant improvements in spherical aberration, curvature of field, sharpness, and image flatness.
The addition of convex (positive) lens on front side and cemented convex (positive) lenses on rear sides made it possible to lower the power of individual lens elements to the conventional Gaussian (Gauss-type) design (Aberration can be reduced by using lenses with lower power, an especially attractive proposition for super-fast lenses).
It also made it more practical than the Sonnar type lens, which in effect corrects aberration with more aberration created by extremely high-powered lenses, a design that makes it more difficult to manufacture and assemble.
If you look closely at the cross-section, you'll notice it resembles AZUMA's 3.5cm f/1.8 lens design (Fig. 2.).
It appears these lenses, which were developed at about the same time, could have been designed by two like-thinking minds who shared technical knowledge and stimulated each other's creativity.
The design executions, however, are markedly different; this is the difficulty and joy of designing photographic lenses.
II. Rendition characteristics and lens performance
What about the characteristics of the 5cm f/1.1 lens ?
Evaluation is, of course, subjective, so what follows is simply a reference point and a reflection of my opinion.
Because of symmetric design, the lens achieves low distortion, small lateral chromatic aberration and high resolving power.
The shape of spherical aberration curve is almost straight.
This is very unusual for a high speed lens.
But a minimal amount of curvature of field appears.
The lens also has very small astigmatism.
Considerable coma remains on the periphery, however, and the flare causes a drop in both contrast and resolving power.
Therefore, when image quality is judged on the basis of residual aberration, the central portion has decent resolving power due to very small spherical aberration, but the large coma at the periphery does significantly degrade performance.
The drop in brightness at the periphery so common in symmetric lenses is also present; the "rugby-ball" vignetting and coma aberration when the aperture is almost fully open can cause an art-shaped vortex of blur to form (see background in Photo 2.).
This is really unfortunate, because the lens has sufficient elements needed for good blurring performance, such as spherical aberration, and a thoughtful aperture design.
The NIKKOR-N 5cm f/1.1 was designed more than 40 years ago, the first of a totally new type of super-fast lens, so evaluation based on modern-day criteria will render skewed results.
I'm compelled to point out that the genesis of the AI Noct-Nikkor 58mm f/1.2 lens (1977) can be traced to the NIKKOR-N 5cm f/1.1, which is more than two decades its senior.
I personally tested and evaluated several high-speed lenses (f/1.2 to f/0.95) from this period, including the ZUNOW 5cm f/1.1.
My conclusion ? The NIKKOR-N 5cm f/1.1 is a standout in its class.
It might even be called unique.
Let me try to explain what I mean by using some sample photos.
From f/1.1 to f/1.4, there is a slight contrast drop in the exact center, but relatively good resolving power. From the intermediate to peripheral regions, however, coma flare gradually degrades contrast and creates a soft photographic veil.
Curvature of field is strong in faraway backgrounds, so resolving power drops off in intermediate regions but improves again in the periphery. [For example, look at Photo 1., and compare the appearance of the woman with the bag at the right (intermediate region) with that of the women on the stairs at the periphery.]
As I said before, blurring can be very ugly, with a "rugby-ball" appearance that creates arcs of blur as in the background of Photo 2.
From f/2 to f/2.8, there is a marked improvement in both contrast and resolving power from the center to the intermediate region.
At f/2.8, the entire image, with the exception of portions of the periphery, is sharp, with excellent blur characteristics.
From f/4 to f/5.6, the entire image is sharp, with excellent blur characteristics.
For portraits, f/2.8 to f/4 would be best.
From f/8 to f/16, the entire image is sufficiently sharp, but contrast will be moderately high.
UDAGAWA, Kazuya, master prototyper
Now, I'll shift the discussion from designers such as Mr. MURAKAMI to master craftsmen and prototype engineers.
Engineers in the prototyping department turn the designers' visions into actual objects. For example, there's Mr. FURUKAWA of the Nikon Corporation Imaging Company Cameras Division, who was designated as one of "150 Modern Master Craftsperson in Japan".
Mr. UDAGAWA is also a top-notch prototyper, consistently offering an array of improvements and ideas that help Nikon retain its competitive edge.
The source of Mr. UDAGAWA's vitality is arguably his hobby : When he's taking a break at work, he's poring over camera magazines, gathering information about old cameras, or visiting used camera stores in search of treasures.
He has an extensive collection of items he's restored, all in beautiful condition. It is this love of fine cameras and lenses that is reflected so strongly in his work.
My own NIKKOR-N 5cm f/1.1 lens, in fact, was one of Mr. UDAGAWA's "patients." It had broken diaphragm blades, lens corrosioned and balsam glue came off. I had all but consigned it to the junkyard.
When Mr. UDAGAWA saw it on my desk being used as a paperweight, though, his eyes lit up with delight : "It's a valuable lens," he said. "Let me resuscitate it, and let's see what kind of pictures it takes !"
It was more of a total resurrection, actually. He got hold of the original design blueprints.
His able friends in the camera shops went to work on the corrosion and the balsam glue coming off.
He personally repaired each blade, one by one, then assembled and adjusted the aperture blades to perfection.
When he mounted the reborn lens on his Nikon SP, he looked genuinely happy.
I still believe that it's this spirit of happiness that makes Nikon cameras great.
The real astonishment came when Mr. UDAGAWA took some photos using the lens.
Though the 5cm f/1.1 did have some peculiarities, he fell in love with it for shooting still lifes and portraits.
A true craftsperson, a true connoisseur of fine cameras and lenses.