Nikon Ai Modifications: The Challenge.

As seen in my previous posts, the vintage Nikkor non-Ai “Auto” lenses are in most cases very suitable for modification/ conversion. The “invisible method” as described earlier, works in most cases. But there are situations where this “invisible method” does not work. Let’s see how it can work.

Nikon made over the last 60 years several iterations for the way the meter coupling tab interacts with the lens. At the introduction of the F mount, there was not even a coupling of lens with camera.

Later executions the meter coupling was established via the rabbit ear: A pin coupled the aperture setting with the camera metering and so the position of chosen aperture was “seen” by the camera and metering was adjusted depending on chosen aperture. These lenses were either Non-Ai or Ai. They had both still the rabbit ears.

Nikon later introduced the DP Photomatic Finders. This option worked with an arm/lever and only worked with Ai lenses. You could still use non-Ai lenses but to do so you had to retract the meter tab arm. In that case you would loose the metering coupling with camera.

This meter tab design was later embedded near the F-mount. A ring, moving around the F mount, with a small rectangular tab that connected the aperture setting of your lens with the camera. By moving the aperture, the ring would move and the camera was able to “read” the aperture setting. All Ai and AiS lenses operated in this way. As you could not use Non-Ai lenses anymore, Nikon provided conversion aperture rings for Non-Ai lenses for a while, basically swapping the original aperture ring with one that had the design to pick up the meter tab.

Although Nikon continued to execute the cameras with meter coupling tabs, Nikon strangely enough, never used a standard blue print for this meter tab. Size and height of this tab changed several times. This is also the reason why original Ai aperture rings are designed in the way they were: maximum backwards compatibility. Old Ai lenses still could fit the newer cameras. Film and digital.

On Nikon budget range cameras, the meter tab was removed. Communication between camera and lens was established via the chip in the lens. New lenses don’t have an aperture ring anymore. Setting the aperture is done on the camera, which tells the lens the chosen aperture.

Luckily on the more pro-ranges of cameras Nikon continued to implement the meter tab. Just to guarantee backward compatibility with vintage lenses. The Nikon Df has the ultimate design: it sits closest to the F mount (0.7mm lower compared to a D800) plus the shape of the tab is tapered. This is the reason why the “invisible methode” works so well with the Df camera for a wide range of lenses.

Getting so many request for lens modifications (and many of them are film based) the question was how to execute lens modifications for other camera/non-Ai lens combinations?

Dealing with so many great customers from around the globe gave me the opportunity to design different custom modifications for them. In the end, I want my customers to be able to use their vintage lenses being it on film or digital cameras. Using a DP11 Photomatic Finder or a digital D850: the lens modification has to be executed in the most elegant and robust way.

Changes needed for these lens modifications happen in tiny areas and are precisely executed in 100th of mm. Sometimes it is needed to place the rabbit ears slightly to the front, which includes drilling new holes and adding screw thread. Or adding a pin at the right position to pick up the meter tab. They are all executed in a robust and most elegant in keeping way.

These lenses were made with such precision and craftsmanship. So please don’t use your Dremel or flat file to quickly modify your lens so it fits your Nikon D5. Although functional, it won’t make you happy to look at and in the end your lens will disappear to the back of a cupboard never to see light again.


Please contact me if you need more information around the modification service I offer.

1 thought on “Nikon Ai Modifications: The Challenge.

  1. Jorma Hevonkoski 12th Nov 2020 — 3:31 pm

    Great and fast service. I’m glad my old 55/1,2 conversion


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