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

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.

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.