NIKKOR - The Thousand and One Nights No.12
NIKKOR-H Auto 2.8cm F3.5
The 10th and 11th Tales discussed telephoto lenses, the AI Nikkor 180mm f/2.8 ED and the NIKKOR-H 300mm f/2.8.
This time I discuss about a wide-angle lens, the NIKKOR-H Auto 2.8cm f/3.5.
This lens was put into the market in March 1960, one year after the introduction of the Nikon F SLR camera. Although the specification is nothing but common one with rather slow in f-number at this time, the lens had been a high-specified wide-angle lens in those days. Moreover, this lens played a quite important role that the SLR camera was recognized as a multi purpose camera.
by Kouichi Ohshita
I. Little lens, Big step
Although various kinds of SLR cameras were went on sale from various companies about the time of introduction of the Nikon F camera, SLR cameras weren't immediately recognized as a multi purpose camera. Speaking of the multi purpose camera of those days, there were rangefinder cameras, capable of exchanging lenses, represented by Leica and Nikon S series cameras.
Accordingly, SLR cameras were thought to be a special purpose camera for shooting telephotography or close-up photography, which were difficult subjects for rangefinder cameras.
No wonder wide-angle lenses for SLR cameras of those days were very few in kind and not satisfactory with very poor in their specifications and optical performance.
As you may know, a SLR camera has a mirror box equipped with a reflex mirror in the body.
Accordingly, a camera lens for attaching to the SLR camera is necessary to have long back focal length in order to avoid hitting the reflex mirror with the camera lens. At that time, a lens type having far longer back focal length than the focal length was not established, so development of a wide-angle lens required a completely new lens type.
On the other hand, in the rangefinder camera, various wide-angle lenses had been developed because of no restriction of back focal length, resulting in the irresistible superiority to the SLR camera.
Under these circumstances, the Nikon F camera released in 1959 was planed to be a multi purpose camera capable of corresponding every shooting condition surpassing the rangefinder camera.
Therefore, it was prime task to develop a high quality wide-angle lens in order that the Nikon F camera became a multi purpose camera.
"Do develop 28mm wide-angle lens having optical performance superior to the W-NIKKOR 2.8cm f/3.5 which had an established reputation for the Nikon S series camera." It was Mr. WAKIMOTO, Zenji, appeared on this series of tales, "NIKKOR -– The Thousand and One Nights", who took the order to take charge of development.
At that time, various companies had been competing to develop wide-angle lenses having a reversed telephoto type (a large diameter concave (negative) lens is arranged in front of an ordinary lens) for SLR cameras with the release of a RetrofocusTM 35mm by Angenieux (France) as the start.
However, satisfactory optical performance could not seem to be obtained without changing the lens construction of known reversed telephoto type including the Retrofocus when the focal length was shortened to 28mm.
Thus, Mr. WAKIMOTO, Zenji found a new reversed telephoto type as a result of trial and error. This is the NIKKOR-H Auto 2.8cm f/3.5 shown in Fig. 1.
As shown in Fig. 1., the lens configuration is a reversed telephoto type (nowadays, this type is called "retrofocus type" turned from the product name) composed of:
- a concave front lens group having a convexo (positive) lens and a concave lens and;
- a ordinary (convexo) rear lens group composed of four lenses having in order of a convexo lens, an aperture stop, a concave lens, a convexo lens and a convexo lens.
The characteristic of the new lens configuration according to Mr. WAKIMOTO is that the lens configuration of the rear lens group is changed from "convexo-convexo-concave-convexo" having been used by conventional reversed telephoto type to "convexo-concave-convexo-convexo".
In conventional retrofocus type, the front lens group is composed of a convexo lens for correcting distortion and a concave lens for increasing the back focal length. However, the original lens configuration of the rear lens group of "convexo-convexo-concave-convexo" could not skillfully compensate coma produced by the front lens group, so it often happened that too much flare was produced at full aperture resulting in unsatisfactory optical performance.
By changing the lens configuration of the rear lens group to that of "convexo-concave-convexo-convexo", Mr. WAKIMOTO drastically improved coma produced on the periphery of the frame, which had been the weak point of the retrofocus type. Thus, a 28mm lens with high optical performance exceeding the W-NIKKOR 2.8cm f/3.5 of an orthometar type (one of symmetrical configuration types) was accomplished.
Although this change of the rear lens group was deceptively simple, the discovery of the lens type was not limited to this lens type. The discovery of the lens configuration of the rear lens group of "convexo-concave-convexo-convexo" broke a way of designing a wide aperture, wide-angle lens for SLR camera with the focal length shorter than 24mm, which was thought to be extremely difficult.
In reality, innovative wide-angle lenses such as the NIKKOR-O Auto 35mm f/2 (1965), the NIKKOR-N Auto 24mm f/2.8 (1967), and the NIKKOR-UD Auto 20mm f/3.5 (1968) had been developed one after another since the development of the 28mm lens expanding the shooting field of SLR cameras.
Please, look at a cross sectional view of a wide-angle lens shown in the current brochure of the Nikkor Lenses. You may easily understand that the lens configuration of the rear lens group of "convexo-concave-convexo-convexo" is included in every AF Nikkor Lenses from the AI AF Nikkor 14mm f/2.8D ED (2000) and the AI AF Nikkor 28mm f/1.4D (1994) down.
Moreover, there are those lenses such as the AI AF Nikkor 28mm f/2.8D having the same lens configuration (6-group, 6-element) as the NIKKOR-H Auto 2.8cm f/3.5.
This happens not only in Nikon. It is not an exaggeration that most of all retrofocus lenses currently sold in the market are modeled on the NIKKOR-H Auto 2.8cm f/3.5.
It would be fair to say that the retrofocus type introduced by Angenieux had really been completed by the NIKKOR-H Auto 2.8cm f/3.5. Although the lens was small in shape, the significance of the development was really great.
II. Lens performance
Let's take a look at how this lens performs with reference to the examples.
The lens with an established reputation for its performance does not yield to any existing lenses. The performance that clearly images the detail of a subject has razor sharpness and power with the aperture fully open. The reputation of Nikkor lenses having sharp and crisp contrast may have established by this lens.
The secret exists in the smallness of coma flare. Even if you take a night view or a star photograph with the aperture fully open, no serious coma flare can be seen. That's the reason why the lens has been habitually used by star photographers.
With the aperture fully open at f/3.5, the entire frame from the center to periphery is sharp and the sharpness and uniformity increase with stopping down the aperture. However, because of sufficient contrast with the aperture fully open, change in image rendition with respect to the aperture is hardly noticeable. As a result, this lens is very easy to use.
(Example 1.) is shot with the aperture stopping down at f/8. You can easily notice that the image is very sharp and distortion commonly associated with a retrofocus type wide-angle lens is very small.
(Example 2.) is shot with the aperture fully open. Since this lens is a wide-angle lens with relatively slow full aperture f-number of f/3.5, large defocus images cannot be expected even at full aperture. However, I like its mild defocus images very much.
At the aperture fully open, brightness of periphery of image field slightly decreases, but it is hardly recognized in the example.
Although the wide-angle lens gives quite faultless images as described above, the only weak point may be the relatively long closest-shooting distance. The lens cannot approach a subject closer than 60cm (2 ft.) from the film plane.
There may have been a prehistory.
Since the lens had very high optical performance with perfectly corrected distortion, the degradation of optical performance according to the closed shooting distance, which is inevitably accompanying to the retrofocus type, was more conspicuous. Therefore, they reluctantly limited the closest shooting distance of the lens to 60cm (2 ft.) .
The closest shooting distance of 60cm (2 ft.) was a little higher performance in comparison with a wide-angle lens for rangefinder camera. Unfortunately, the merit of a SLR camera suitable for shooting at closed distance without parallax could not be put to practical use by the specification.
The user's demand for shooting by a wide-angle lens with getting close to a subject had gradually become strong. The demand led to the development of the NIKKOR-N Auto 24mm f/2.8 equipped with a close-distance-correction mechanism. However, I would like to tell you this story at some other time.