Nikon’s Roots Vol. 07 – Nikon Auto 35

The final lens-shutter SLR model

The Nikon Auto 35, released in 1964, was Nikon’s last lens-shutter SLR. As a fixed-lens shutter single-lens reflex film camera, it clearly belongs to a series of products starting with the Nikkorex 35, but this model was the only one released under the trade name “Nikon” (the export version was called the Nikkorex Auto 35). In later years, the final model in the Nikomart series was also the Nikon EL2. Is there a rule that the product name representing a popular Nikon model changes to Nikon when it is the last model in the series?

However, in the case of the Nikkorex, as mentioned earlier, it had a bad reputation for having many breakdowns, so perhaps there was an intention to break free from that curse.

Viewfinder turned into a pentaprism

In any case, as the last Nikon lens-shutter SLR model, it was the result of efforts to somehow solve the problems that had been pointed out up until then. First, the Porro mirror finder, which was a major feature of the Nikkorex 35, was abolished and replaced with a regular pentaprism finder. The reason is probably the viewfinder magnification. By using a pentaprism, the optical path length of the eyepiece can be shortened, increasing it from 0.6 times with a porro mirror to 0.82 times.

By using a pentaprism, the top surface of the camera body is flat, rather than having a sharp head like a regular SLR camera. In other words, both shoulders of the upper cover (warship) are raised to the top of the pentaprism. The space on the right shoulder (winding side) is used to store a large ammeter and meter-pressing aperture control mechanism, but the left shoulder (winding side) is completely empty. The rewind knob and film counter mechanism have been raised with pillars to accommodate the raised upper surfaces of both shoulders. The rewind knob is also designed to pop out when in use, making it easier to operate. The shutter button is difficult to press if you’re tall, so it’s placed on the front of the body so you can press it diagonally.

An example of using a pentaprism with a flat top surface is the Pentina of East Germany, but it is not often seen. Was there something that the designer was particular about?

Quick return mirror

One thing that Nikkorex series lens shutter SLR cameras lagged behind others was the adoption of a quick return mirror mechanism. A quick-return mirror is already a common feature in focal-plane shutter SLRs, and it was realized in the Topcon wink mirror released about six months after Nikkorex 35, and rival Canon also introduced the Canonex in 1963. They are releasing a quick return mirror lens shutter single-lens reflex camera. As a successor to Nikkorex 35II, it was essential to adopt a quick return mirror.

However, it was not easy to implement a quick return mirror in a lens-shutter SLR camera. When the camera receives a signal from the shutter mechanism that the exposure is complete, the key that prevents the mirror from moving down is released and the mirror is lowered. The spring force of the shutter blade drive is used to signal the end of the exposure. I just couldn’t find the strength to remove the key properly. A focal plane shutter can pick up a signal of sufficient force from a strong spring that drives the rear curtain, but a lens shutter does not have such a strong spring because it only needs to move the shutter blades lightly. Therefore, the start of mirror down tends to be unstable. The Ultramatic, the successor to West German Voigtlander’s lens-shutter SLR Vesamatic, incorporated a quick return mirror, but the fact that the improved version of the Ultramatic CS returned to a specification in which the mirror was raised all the time made it difficult. It tells a story.

As a countermeasure for this lack of power, the Nikon Auto 35 seems to have used a type of mechanical amplification device, which is equipped with a separate spring to unlock the mirror down, and charges it in conjunction with the winding.

Shutter speed priority Auto Exposure

The first half of the 1960s was a time when automatic exposure began to become popular. The technology mainly used in lens-shutter cameras is called the “meter holding method” or “step cam method.” The position of the pointer of the exposure meter is detected by a stepped cam, and the aperture is adjusted at the position where the cam touches the pointer. It was a decision. Single-lens reflex cameras equipped with this type of automatic exposure appeared from the lens-shutter Kowa H (1963) and the aforementioned Canonex, and later spread to focal-plane shutter cameras.

Following this trend, the Nikon Auto 35 also incorporates shutter speed-prioritized automatic exposure using a meter press method. This camera was the first Nikon camera to have an automatic exposure system, and the only one to use a meter hold-down system.

Newly designed photographic lens

The shooting lens is the newly designed 48mm F2, which is brighter than the Nikkorex 35. The configuration is a Gauss type, built with 6 elements in 4 groups. Like the Nikkorex 35, telephoto and wide-angle front conversion lenses are available, and when attached, the lenses become 85mm F4 and 35mm F4, respectively. Adapters for close-up lenses and microscope photography were also available, but the most interesting one was the binoculars adapter. The composite focal length is the value obtained by multiplying the magnification of the binoculars by the focal length of the photographing lens, so the idea is to easily enjoy the super telephoto effect, but it is rare for single-lens reflex cameras. However, it is questionable how practical it was.

The end of the lens shutter SLR camera

In the 1970s, 35mm lens shutter single-lens reflex cameras disappeared. One reason for this is that focal plane shutter cameras have become relatively easy to manufacture with the advent of unit shutters like Copal Square, but lens shutter SLR cameras are also prone to failure due to their mechanical complexity. It must have been a big deal. Just as the Nikkorex had a bad nickname due to unreliability, I heard that the Nikon Auto 35 was given the unfortunate nickname “Nikon Out 35” because of its frequent breakdowns.

With the Nikon Auto 35, Nikon also gave up on lens-shutter SLRs and moved to the Nikomart line as a popular model.