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  6. Tale 3 : W-NIKKOR 3.5cm f/1.8

Symmetric High-Speed, Wide-Angle Lens Tale 3 : W-NIKKOR 3.5cm f/1.8

"S"- mount and "L"-mount
W-Nikkor 3.5cm f/1.8 lens

The third tale discusses the W-NIKKOR 3.5cm f/1.8, our "S" / "L"-mount interchangeable lenses.
This lens, first released in September 1956, is the brightest wideangle lens in the world. The body associated with it was the Nikon S2, but this was followed by the SP the following year, then the S3 the next, so you should understand that it was developed to match the concepts and designs of the SP and S3 as well.

The optics were designed by Senior Manager AZUMA, Hideo of the Optical Design Section, and the design was completed in the winter of 1955.
Azuma was one of the teachers of WAKIMOTO, Zenji (mentioned in the first tale), and had extensive experience in designing "S" / "L"-mount Nikkor lenses.
He made an enormous contribution to improving Nikkor lenses, especially in laying the foundation for aberration balancing.
At the time he was active in the field, Dr. Ludwig BERTELE was also active in the field in Germany.
This expert Japanese designer is little-known outside the industry, but his achievements can be traced through his countless reports and patents.
He filed the patent application for the large-diameter, wideangle lens in 1956, and was granted the U.S. patent in 1959, signifying general recognition that this was indeed a new type of lens.
At that time, most 3.5cm lenses were in the f/3.5 to f/2.5 range, and this was the first lens of f/2 or faster in the world.
It took another one to five years for competitors such as Ernst Leitz to develop similar lenses.
At that time, the tools of the designer were the abacus and the logarithmic table...... a staggering amount of computation and time must have been needed.
To be a lens designer back then required enormous determination and
devotion.

1. Structure and features of the W-NIKKOR 3.5cm f/1.8 lens

Cross-section of W-Nikkor 3.5cm f/1.8 lens

This discussion will be a little more difficult, but please bear with it.
First, take a look at the cross-section of the W-NIKKOR 3.5cm f/1.8 (Fig. 1.).
It is pretty clear that this is based on the symmetric lens type.
From the left there is a convex lens, a compound convex/concave cemented lens, a diaphragm, a concave lens, convex lens, and then another convex/concave cemented lens.
The external appearance up to this point is similar to other Xenotar-type lenses, but the design utilized the totally new Lanthanum (La) -based glass convex lenses to improve spherical aberration and curvature of field, significantly enhancing both sharpness and image flatness.
The key feature of this lens is the cemented lens at the back.

Also called a doublet, this cemented lens improves the spherical aberration and coma so common in high-speed lenses.
It also provides a major improvement in correcting lateral chromatic aberration (peripheral discoloring, smear).
The concave lens closest to the film surface serves as a field flattener.
It is quite difficult to design a high-performance lens with a picture angle (angle of field) of more than 62 degrees as a simple Gauss-type lens.
And back then, it must have been astounding to produce such a large-diameter, wideangle lens. Even in comparison with the designs of later manufacturers, the superiority of AZUMA's design stands out, because other designs are still fundamentally Gauss-type.
Two or three lens are cemented together in an attempt to cancel out the aberration generated at the lens surface.
AZUMA 's design, on the other hand, it significantly advanced in terms of manufacturing ease and compactness.

AZUMA 's new lens type became the model for a host of new lenses.
At about that time the camera industry evolved to the SLR, and his designs were largely forgotten.
Alert readers will have noticed, however, that new lenses built on this basic type are appearing recently.
The very latest lens design seems to have settled on this concept, again pointing up the superiority of the design.
I am sure AZUMA would be proud to know that his invention still guided the industry 40 years later.

2. Performance of the W-NIKKOR 3.5cm f/1.8 lens

It is difficult to evaluate the performance of the W-NIKKOR 3.5cm f/1.8 lens, because so much of evaluation is subjective.
Think of what follows as a personal opinion presented for your reference.
As mentioned above, this lens is symmetrical, which means it has low distortion.
It also had very low lateral chromatic aberration, which is a key factor in assuring high definition.
The image is flat and astigmatism minimal all the way to the periphery.
There is a slight drop in contrast due to coma flare around the maximum aperture setting, but even so definition is excellent, and lines are crisp.
The aberration balance is representative of lenses decades ago.
The lens also suffers from a drop in peripheral light intensity, as is so common in symmetric wideangle lenses.
This could present a problem when using positive film.
The outstanding feature is that there is no unnatural bending of the light source.
I don't remember ever seeing a picture, even when the light source was a neon sign at night, that looked unnatural.
The defocus image around the maximum aperture periphery is very soft and nice.

Next I will touch on performance at various apertures, using sample shots.

Nikon SP, W-NIKKOR 3.5cm f/1.8,
f/2.5, 1/15 sec.
Film : FUJI Neopan 400 Presto
Developing : Microfine 1:1 dilution
Paper developer: Correctol
Paper : ILFORD Multigrade
(Grade 2 equivalent)
(C)1995 SATO, Haruo

Definition from f/1.8 to f/2 is excellent, and the expression shows a slight drop in contrast, with a soft touch like a thin veil.
With the exception of a very small peripheral region, flare is uniform and contrast compression adequate, preserving rich gradation.
Low astigmatism minimizes "stream" on the periphery, and while the periphery is a bit darker, it rarely presents a problem in monochrome shots.
Photo1. is a representative shot at f/2 to f/2.8.

Definition and contrast both show improvement between f/2.8 and f/4.
In particular, the central region is extremely sharp.
However, the soft touch is not lost.
The darkening around the periphery is improved to the point it no longer represents a problem.
In Photo 1. the focus has been set for the man's feet, floor and tiles (slow shutter speed and object motion resulted in a little blurring; sorry about that).
The defocus image of the background is excellent, and point sources show no bizarre deformations.
This range, from f/2.8 to f/4, is a good choice for indoor shots, night-time shots, and portraits.

Nikon SP, W-Nikkor 3.5cmf/1.8, f/11, 1/500 sec.
Film : FUJI Neopan 400 Presto
Developing : Microfine 1:1 dilution
Paper developer : Correctol
Paper : ILFORD Multigrade
(Grade 2 equivalent)
(C)1993 SATO, Haruo

Between f/5.6 and f/8 the sharpness and clarity are even better, with excellent rendition over the entire image area.
This balance of gradation and definition cannot be attained merely through high contrast.
This range is best for outdoor shots and scenery, I think.

The same tendency appears from f/11 to f/22.
This level can result in photographs with strong contrast, but even with Grade 3 black-and-white paper and straight development, I can't remember ever having white-out sky tones.

Photo 2. was shot at f/11, and even though it was developed straight the gradations on the corrugated sheeting are excellent.
I have never had any trouble with ghosts.
Compared to other large-diameter, wideangle lenses it has a low number of lens elements and plenty of design margin, minimizing ghosts.

The first article in the series, on the Nikkor-O 2.1cm f/4, has received excellent reviews from lens fans, therefore we picked another old lens. How was it ?
We'll switch back to a more modern design lens next time.
See you then !

Note

This issue first appeared in "NIKKOR Club Quarterly" magazine, published by the NIKKOR Club, and was revised for Nikon's webpage.
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