Sunday, February 9, 2025

Nikon’s AI Manual Focus Lenses Refer to “Auto Indexing” not “Artificial Intelligence”

 



 

I have been following the new wave of new cameras, some using film, others digital but looking like vintage cameras.  The latter seem to follow the periodic nostalgia humans have to fashion, the arts and perhaps values. Interestingly, some of the “new retro” looking cameras is advertised as having the feel of vintage ones.

I have never owned a digital camera, but did try a few my friends strongly suggested I should experience. I have always returned to my black boxes with a few shutter speeds. The reason has been two-fold: partnership and feel. Like any artist or artisan using a tool, creativity is undeniably related to the joy of using that tool. And sometimes, it is the journey through that partnership that provides the satisfaction and pleasure, no matter the outcome.

So, as I was reading that some of the new cameras are now made in metal not “plastic”, I looked at the shelves where my cameras are organized by maker, rangefinders separate from SLRs and medium format TLRs, including the section where non-functioning cameras and partially dismantled ones are displayed. The latter have been my “organ donors” to repair ones that suffered untimely ailments…

In the Nikon section, my eyes fell upon the 1982 FG. I had bought it to complete my collection, but the moment I handled it almost a quarter century ago, I knew it will not be the tool that would be my partner in creativity, nor provide the feel during the experience.

But, over the years, I have periodically pushed myself to give it a second chance, ignore the un-nikonness of it, pretend that the film advance lever was a smooth as a Nikon F3, that the metering was revolutionary, and that it fit in my hands like gloves made of Peccary leather.

I used it last a year ago (https://liveingray.blogspot.com/2024/07/prescott-arizona-2024-july-4th-frontier.html) but as always, I put it back on the shelf, knowing that I will again get the urge to find a reason as to why I own it.

A few days ago, reading about new cameras, I wondered how it will feel and use a 1970s all-metal and glass lens that was at least 3 times heavier than the FG itself. And that lens was the first version of the 1970s Vivitar Series1 70-210mm zoom made by Kiron, made for the Nikon F. I had used that lens decades ago on my 1968 Nikon F to take school soccer game photos. I recall, even then, a few parents wondering what kind of prehistoric camera I was using. So, it has been sitting on the shelf since.

Here is the Vivitar Series 1 lens



And its imposing presence!



But with the urge of using it on the FG, I went downtown Prescott to test the new contraption.

The zoom range is certainly not suitable for street photography, nor is the size/weight of the lens for quick handling. And, forget about candid shots when people see that massive tube in front of my face! However, I managed to take a few shots using the FG’s aperture priority mode at f11 aperture. The photo at the top of the page is my favorite, and I will discuss it later, but given the history of the lens, a few words about the evolution of Nikon SLR camera mounts seems appropriate.

A quick history of Nikon lens mounts

The first Nikon F camera was produced in 1959 and had a patented “Nikon Bayonet” mount. The lenses made for that bayonet mount had an aperture coupling prong (sometimes called rabbit ears) coupled with a small lever on the external Photomic light meter unit and, after a full rotation by the photographer of the aperture ring, the rabbit ears “told” the camera what aperture the lens was so the light meter can indicate the appropriate speed in the viewfinder.

It was not until 1977 that Nikon introduced to the bayonet mount a structure leading to a new way of coupling the aperture ring to the light meter. It was called AI or Auto Indexing AI lenses have a ridge that catches a feeler on a ring surrounding the lens mount on the camera.

While non-AI lenses’ rabbit ears had to couple with the light meter lever and the photographer had to rotate the aperture ring to inform the light meter about the lens, now AI lenses had an internal mechanical structure that immediately upon mounting the lens, informed the camera about the maximum aperture of the lens allowing the light meter to get ready for the correct metering using that specific lens. So, from 1959 to 1977, not only all Nikon SLR lenses were Non-AI (sometimes also called Pre-AI) but there were third party lens manufacturers who produced a plethora of Non-AI lenses. None of these lenses had the quality or performance of a Nikon, but many stood out with their creativity and surprisingly impressive results. The first Kiron made version of the Vivitar Series 1 70-210mm was among those that shined (there were 6 versions of that lens but none achieved the performance of the first version, the only one that was Non-AI).

Nikon continued the tradition of the rabbit ears, to visually identify them as AI. But more importantly, the AI lenses could still be mounted and used on the older F-mount cameras.

Finally, given the sublime built and performance of Non-AI lenses, Nikon (and others) made upgrading rings with that famous groove to allow Non-AI lenses behave like AI lenses on the post 1977 Nikon mounts. These metamorphosed lenses are called AI’d allowing seamlessly the use historic Nikon lenses on newer Nikon cameras.

Visual difference between Non-AI and AI lenses

The original rabbit ears for the Nikon F bayonet mount are solid metal. Here is the venerable 50mm f1.4 Nikkor-S Auto from 1964.

 


All professionally AI’d lenses had the new ring added to the lens and perforated rabbit ears. The new conversion ring added a second, in smaller numbers, set of aperture numbers to the lens. These changes can be seen on my 1971 Nikkor- P 180mm f2.8 lens.

 


And then there are non-professional conversions. These are the most creative ones (when they work) and shows how much owners cared about their old lens and wanted to continue using them post 1977. I have seen quite a few such creative conversions, but the one done on my Vivitar 70-210mm is the most unusual but it works! Whoever did this was a minimalist – he added a home-made T-clip to the existing aperture ring to catch the new groove of the Nikon mounting base and make the 1972 Vivitar Non-AI zoom lens AI’d!  Perhaps it is fun to use this lens just for this peculiar characteristic?

 


Why did I go into this long explanation? First, hopefully some readers will find it interesting as a historical overview, but also because I have many of those AI’d lenses that continue to provide the vintage look to photography none of the modern Nikon lenses can. Perhaps to the avid B&W photographer, they would provide a unique experience.

But, the photo at the top of this page says otherwise. I was genuinely surprised by the sharpness of the result as I took the photo handheld, at full zoom and f11 from about 50 meters of the memorial statue. The contrast is low, as expected, even with the makeshift lens shade I made. But with no zoom creep, the focusing is very reliable and the sharpness of the lens is truly surprising. Here is a cropped section of the inscription on the memorial, which was the spot I focused on hoping that, the two gentlemen (and the dog) sitting a few meters in the background will be more blurred. Too bad I did not have the chance to take a second shot at f4….

 


I knew that the heft and width of the Vivitar lens felt just right in my hands and I was able to remain very steady, something I had never managed when using the FG with smaller and lighter lenses.

Is it possible that, after 25 years, I have found the right lens-camera combination for the FG?

 

February 9, 2025

© Vahé A. Kazandjian, 2025

 

PS/ I realise that many young photographers have not seen or used a Non-AI lens fitting the Nikon F, nor perhaps the AI lenses that made the Nikon 2 and Nikon 3 milestones in photographic history. Yet, I find it a timely retrospective trip to see what the term AI once meant to those who ran miles of film pellicule through their cameras and spend endless hours in makeshift darkrooms to burn or dodge a 5x7 or 8x10 photographic paper under the faint light of an enlarger.

And, what AI means today to those who have all the technology in their hands and can see, the instant it has been taken, the photo on the screen back of the camera. And, in full sunlight, they can edit those photos with AI.

For me, washing the printed paper with cold water in the darkroom sink, surrounded with the lingering aroma of the Stop Bath solution (for those who still remember what that is), is a pleasure I am not ready to forego.