Nikon F-Mount: 60 years from Auto to K(aizen)-Lens.

From early 1960 up to 1974 the external lens design of Nikon Nikkor lenses was basically the same. All the parts were made out brass, aluminium, and of course glass. Small design changes were made in construction, and many of these design changes had to do with bringing down the cost and quality up.

Looking at a so called ”Auto” lens (nothing to do with autofocus) you can clearly see this at the bayonet mounting ring. Nikon started with a screw-less design. The bayonet ring was fixed basically invisible: 3 screws from the side, covered by the aperture ring that had to be screwed on. The next generation, the bayonet was fixed by 4 or 5 slotted screws. The aperture ring was simply placed onto the lens barrel and the bayonet was screwed onto the barrel, locking in the aperture ring. This construction was far more simple and surely cost effective: gone was the need for fine screw thread on the barrel of lens and aperture ring. Easier assembly, reducing assembly tact time.

With the introduction of screws, Nikon also introduced glue to secure the screws. It was a measure to improve quality and robustness.

In later models, the slotted screws were replaced by Japanese cross head screws (JIS type). These screws are easier to handle, less prone to damage and therefor speeding up the assembly and reducing cost of operation.

Nikkor F mount Auto lenses: 3 generations from 1960 till 1973

By 1974 Nikon Nikkor introduced the so called K-type lens. This lens is recognisable by the rubber focussing ring, replacing an aluminium extruded part that had to be precisely machined and coated. Beside this, new coatings were introduced and some faster lens designs.

In marketing terms the Nikkor K-Lens offered: reduced weight & no cold fingers anymore. But in reality it was a significant cost saving for Nikon’s operation. Beside significant material reduction, the whole manufacturing process could be simplified, meaning less process steps, less material handling and reduction of non conformity products. Quality remained still key. This was a real great example of a Kaizen: Change for Better.

At start of roll out of these K-lenses back in 1974, Ai (Auto Indexing) still had to be introduced. This happened in 1977 by the introduction of Ai-lenses. It was a mechanical connection between lens and camera for metering purposes. Followed in 1981 by Ai-S lenses.

Ai and Ai-S lenses have an aperture ring that picks up the metering tab located on the camera. Nikon introduced a service to replace the non-Ai aperture ring for an Ai-aperture ring, and so guaranteeing their customers compatibility of old lenses to be used on newer type of cameras. Even today, a significant part of the Nikon camera line-up still has the same metering tab. As such, these old Ai-lenses can still be used on modern DSLR without any problem. This type of product support and compatibility you don’t see that too often these days with some new products having a maximum lifespan of 3 years (or less).

Nikon eventually stopped the service to replace the Non-Ai aperture ring for an Ai-ring, and so conversion by users was introduced. Most of the Auto lenses prior to 1977 can be converted to enable metering by the camera. The material thickness of aperture ring of early Nikkors allows great invisible conversion as you can see on my other blogs. Some of the K-lenses can also be converted, however slightly different, depending on the diameter of the aperture ring and type of camera used. But main thing is: they still work.

Nikkor 300mm f4.5 K-lens conversion

With the introduction AF (autofocus) and Digital camera’s, the function of the aperture ring was slowly taken over by electronics in camera’s and lenses. Current G-lenses do not have an aperture ring anymore to select aperture. Aperture setting is now done by a selector on the camera.

This year, it is 60 years since Nikon introduced the F-Mount. The significant amount of lenses introduced by Nikon still all work on modern DSLR’s and even on their new mirrorless camera’s although with a necessary adapter.

The fact that Nikon still keeps supporting this F-mount, 60 years after introduction, should really be more appreciated and perhaps more celebrated.

Nikon F-mount

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