Killing a Nikkor AF-D lens cpu: whats behind a Micro-Nikkor 105mm f/2.8 AF-D internals?

This is a short Dunning-Kruger tale about an attempted repair of a Nikkor AF-D lens that was misreporting its max aperture and somehow killing the CPU - the dead CPU means that the DSLR body no longer recognises a CPU enabled lens which means no autofocusing (even on motor-enabled bodies), no metadata and no body controlled aperture - only dumb manual focus operations available.



How did it happen? I don't know and it shouldn't have happened as I've worked/repaired with fragile electronics for over 3 decades but yet here we are. A story of interest and what makes up the mechnical-CPU enabled internals of a Nikkor AF-D lens.

Cleaning Optics of a Micro-Nikkor 105mm f/2.8 AF-D

The 105mm macro lens has its origins in the 1960s and 1970s with the legendary 55mm macros and eventually deliverying its 105mm f/4 and f/2.8 variations from the lates 1970s into the mid 1980s . As with lenses of that era they were only capable of 1:2 reproduction ratio, even with the 1984 105mm f/2.8 AI-S. Work on the AF macro lens started in 1987 with full redesign (including optical rework) completed and release in 1990 with a priority to support autofocus and push the maximum reproduction ratio from 1:2 up to 1:1 (life-size) and eventually in 1993 the AF-D was released, with changes for the distance encoder

As with many old lenses cleaning of the optics might be necessary and the following appears to be only source to document front, middle and rear elements.

Bargains No More in HKG

Tokyo and Hong Kong were once a great place for hunting vintage Nikkor lenses but over the last few years this status seems to have shifted in terms of expectations towards inventory and pricing.

Junk Vintage Lens Hunting in Tokyo

Japan still seems to be a treasure trove for vintage Nikon cameras and Nikkor lenses but it may not be the same level of surplus that it once was, especially for junk items. Central Tokyo's normal outlets have started to get more recognition for tourists and locals alike hunting for bargains and heres a few of popular stores.

Sleeping Legacies: Nikkor AI/AI-S Cult Classics

Many new comers exploring Nikkor's vintage F-mount AI/AI-S lineup are usual presented with the same set of legendary lens, but its often worth considering the rest of the expansive Nikkor catalog. Whilst there are poor lenses in the historic Nikkor lineup, there are other lenses which are often overlooked by the mainstream and they exist with their own cult statuses.

Lazy tooling: Magick Image Annotations

Preparing various images of different sizes for a standardised dsiplay can be hugely time consuming and manual. How can we be lazy about this?

Short Tele, Alternative Legacy: The 85mm f/2 AI-S

When discussing short Nikkor telephotos or classic portrait lenses, a number of lenses come to mind: the 105mm f/2.5 AI-S and the 85mm f/1.4 AI-S. However there was another: the 85mm f/2 AI-S.


^{85mm f/2 AI-S sitting between a 105mm f/2.5 AI-S and 50mm f/1.8 AI-S pancake}

An economical wide alternative: 28mm f/3.5 AI

The 28mm f/3.5 has a long history reaching back to 1960, with the Auto-H, and cumulating in the Nikkor 28mm f/3.5 AI/AIS of the late 70s/early 80s. All variations had a 6/6 design although the Auto-H and the AI/AI-S having different optical formula. By the time the AI/AI-S was released in 1977/1981, it was already seen as the economical 28mm with its slower f/3.5 max aperture with the f/2 K and f/2.8 K/AI making its debuts in 1975 and 1974 respectively.

The f/3.5 AI-S was sunset in 1983 by which time the very well regarded 28mm f/2.8 AI-S had been released. Over time, the 28mm f/2.8 AI-S reputation (and its long production run) keeps it in conversations but if you were to consider a manual 28mm, is the slower f/3.5 worth considering?

A joyless jaunt: 135mm f/2.8 AI Repair/Service

The 135mm f/2.8 AI was produced from the 1977 - 1981 and lived in the shadow of its faster f/2 sibling and also had competition from the 105mm variants. Its a compact rugged lens but its not a lens I'd seek out myself except to rip it apart for curiousity

Reverse the macro trend: the Nikon BR-2A Macro Adaptor Ring

Getting into macro photography has its challenges, typically given the need for a suitable lenses. However, there is another option with reversing ring such as the Nikon BR-2A that can be used your existing lens.

Widely Regarded: Nikkor 20mm f/4 AI

The Nikkor 20mm f/4 AI (and its near identical predecessor, the K) was the optical successor to the very well regarded Nikkor-UD 20mm f/3.5 Auto. The K was produced from 1974 to 1977 and the AI released for a short period after til the start of 1978, at which point the Nikkor 20mm f/3.5 AI had been released. Both the f/4 AI and f/3.5 AI lenses had good reputations - with the f/4 AI lens' reputation enhanced by well respected nature photographer Galen Rowell's recommenation - but how good are they really?


^{Nikkor 20mm f/4 K with factory AI conversion aperture ring}

Precision Macro: Using the Nikon D300 with LiveView and Focus Peaking on Linux

Macro photography is a game of millimeters. When you are shooting at 1:1 magnification, the depth of field is so thin that even the slightest movement or a poorly calibrated viewfinder can ruin a shot.

The Nikon D300, while a solid workhorse even more than a decade and a half later, lacks the modern "Focus Peaking" found in mirrorless cameras. However, with a Linux machine, some open-source tools, and a custom Python script, we can give legacy liveview enabled DSLR real-time focus assistance.

The Designated (JIS) Driver

The general guidance for vintage Japanese lens repair is to use JIS drivers to avoid stripping the screw heads so what and how many do we need?

Serv(ic)ing A Micro legacy: Micro Nikkor-P Auto 55mm f/3.5

The Micro Nikkor 55mm f/3.5 series of lens has had a long history with the first iteration arriving in 1961 and lasted nearly 20 years with the same optical formula, cumulating in the Micro Nikkor 55mm f/3.5 AI. Of course, the 55mms prior to the AI version were all pre-AI although Nikon provided factory AI aperture ring conversions and its reasonable rare for still find a pre-AI factory converted 55mm. I found a late edition (1969-73) factory converted P-Auto and give it a service and here's what I found.


^{Micro-Nikkor P Auto 55mm f/3.5, with factory AI conversion and non original rubber grip}

Nikkor 20mm f/3.5 AI repair / service

I've loved this lens for a while now for its a ability to resist flare like no other vintage Nikkor I've used, but I've put off servicing this lens since theres been NO online repair resources/service manuals available, not even from the usual places that may have alerted us to identified gotchas. In the end, I decide to attempt the service regardless given recent successes in servicing other Nikkor AI/AI-S lenses.

Old school shade - vintage lens hoods

Rick Housh's archived Geocities Lens hood page was the bible for helping us finding the right lens hood for our vintage Nikkors - whilst this is archived on OOCities.org I've found it a little slow and tempermental. Rick's original domain http://housh.net has long gone sadly and it reminds us that the internet is very much fragile and we hope other resources such as Roland Vink's phenomenal Nikkor lens db is maintained - Roland's pages list the official lens hood for each lens but without hood dimensions etc.


^{Nikon HK-6 for 20mm f/3.5 AI}

Commodity old school 35mms

The 35mm focal length was a classic "candid" lens, for street photography/photojournalism etc but for me it was always a compromise: neither wide enough or long enough, preferring either a 28mm or a 50mm/85mm/105mm. These 35mm still command a decent price on the used market and I was able to obtain a 5/5 element/group 35mm f/2.8 AI-S and a 8/6 35mm f/2 AI for a short evaluation.

Cleaning, Repairing and Servicing a 50mm f/1.4 AI

The 50mm f/1.4 AI and its optical formula was inheritted by its successor and beyond which meant it was in production from the late 70s to 2025 so this lens as an option comes with a well known optical performance and can be found a slightly lower cost than its succesor. The f/1.4 AI ran from 1977-1981 so servicing is a must, with my copy having sticky and unusable focus as well as being very dirty.

Just One More: 50mm f/2 AI

Having serviced and owned a number of Nikkor 50mm I asked myself how many 50mm do we actually need? It turns out that just one more in the shape of a 50mm f/2 AI.

Helicoid Grease options: Japan Hobby Tool #10 and NPC FC-4 / BC-13A

Helicoid grease is a specialist item that is difficult to source and suitable options are limited. Even with options, the lens manufacturers do not disclose their greases and there are a very limited number of trusted resources that have reviewed various the greases. Two greases that are under consideration are Japan Hobby Tool #10 and NPC FC-4 (reportedly the grease used in some Nikkor lenses)