Nikon has a long history of producing great lenses for the 35mm format, beginning in the post-WWII era with rangefinder lenses and continuing through its many famous SLR cameras and into today's digital camera lenses. Many of the legends from the Nikon F / F2 / Nikkormat days are still great lenses because they were built so well, and they are often available at very low cost because 1) they are manual focus, and 2) they cannot safely be mounted on most cameras built after 1977 because they may damage the meter coupling system. The AI (Automatic Indexing) meter coupling tab may be bent by the straight-cut aperture ring of the older Nikkors, and the minimum-aperture sensing switch on many autofocus and digital models can be damaged as well.When Nikon introduced AI lenses they made replacement aperture rings to convert some of the older Nikkor lenses. Those factory rings are pretty hard to come by for the most popular lenses, and expensive when you find them. In this listing I offer an alternative: milling the existing aperture ring to the AI profile to duplicate the effect of the Nikon factory replacement ring.Here's the process: I remove the aperture ring from the lens and use a Dremel drill press with an end mill bit to make precise cuts in the back end of the aperture ring to match the AI profile for the particular lens model. The profile varies according to the maximum and minimum apertures available. Some of the homegrown modifications you see on lenses offered on eBay are wildly off, like they just copied the ring on some other AI lens they had; I stick to the Nikon spec for each lens. This is a full modification, not a partial modification just to create the AI ridge such as is offered on some web sites. After milling I carefully finish and repaint the bare metal, and when there is space and a flat surface I place a printed label with the ADR numbers, white-on-black like the real thing. Please view the photos for some in-process views -- immediately after cutting, a cut with the meter coupling shoe left in place, a modified ring after priming and painting, and the finished product viewed from the lens mount end.Thus modified, it can be mounted safely on any Nikon SLR (including AF and digital), although metering functions may be limited or unavailable on later electronic models -- check your camera manual for details. Also, Nikon names a few lenses which can never be mounted on certain electronic and digital bodies even with the factory conversion, so be sure to check your manual if you have an unusual lens. Many of these (such as the 55mm f/1.2) can be made safe with a small additional modification, so ask me about that. For digital users, this modification will NOT interface with the meter on D50, D70, D80, D90, or D100 models, but can be used in aperture-priority mode with D1, D1H, D1x, D2H, D2x, D3, D3s, D3x, D200, D300, D700, and D7000. Note for D40, D40x, D60, D3000, D3100, and D5000 owners: you do not need this modification. Pre-AI lenses can be used on those bodies without modification, but only in full manual mode -- manual focus of course, manual aperture and shutter speed selection.I will return your pre-AI meter coupling shoe in case you wish to re-mount it for compatibility with older cameras. Or if you tell me in advance, I can leave the shoe on the aperture ring during milling so that it will be ground even with the cut I make in the ring. If you choose this option there will be no ADR numbers added.This service is available for most pre-AI Nikkor lenses. I have modified the following:
* 6mm f/2.8 fisheye
* 8mm f/2.8 fisheye
* 15mm f/5.6
* 16mm f/3.5 fisheye
* 18mm f/4
* 20mm f/3.5 & f/4
* 24mm f/2.8
* 28mm f/2, f/2.8, & f/3.5
* PC-Nikkor 28mm f/4
* Zoom-Nikkor 28~45mm f/4.5
* 35mm f/1.4, f/2, & f/2.8
* PC-Nikkor 35mm f/2.8 & f/3.5
* Zoom-Nikkor 43~86mm f/3.5
* GN-Nikkor 45mm f/2.8
* 50mm f/1.4 (all versions)
* 50mm f/2
* Zoom-Nikkor 50~300mm f/4.5
* 55mm f/1.2 (includes lens surround modification to permit use on F4)
* 55mm f/3.5 Micro-Nikkor
* 5.8cm f/1.4 (includes lens surround modification when needed to permit use on later bodies)
* Zoom-Nikkor 80~200 f/4.5
* 85mm f/1.8
* Zoom-Nikkor 8.5~25cm f/4-4.5
* Zoom-Nikkor 85~250mm f/4
* 105mm f/4 Micro
* 105mm f/2.5
* 135mm f/2, f/2.8, & f/3.5
* 180mm f/2.8
* 200mm f/4
* 300mm f/4.5
Nikon used several mechanical designs to attach and link the aperture ring, but I believe I have seen and successfully worked most of them.Some early models and some very late (K-version) models have a smaller diameter aperture ring which needs to be built up with a small metal plate in order to engage the AI tab. I have seen this on some models of the 20mm f/3.5 UD, 28mm f/3.5, early models of 3.5cm/35mm f/2.8, and the early Nikkor-S 5cm (50mm) f/2. There may be others. I mention this as an appearance issue, and I will let you know after inspection whether your lens will need this. Photo #6 shows thisbuildup on an early 3.5cm f/2.8 lens.If your lens is not listed above, please check with me. It is most likely I still can modify it. If it is an early model, the kind with no visible screws holding on the lens mounting flange, I definitely can modify it. Naturally, if I find I cannot safely remove the ring due to its design I will return the lens and refund your entire payment (including the amount designated for return shipping). Please note: occasionally I find a lens which has been worked on before (cleaning, maintenance) and the repair shop used glue or Loctite to seal the mounting screws in place. If I can't remove a necessary screw without destroying it, I will refund the price paid but not the return shipping amount. This hasn't happened yet, but I have had to put great time and effort into removing some screws.When I receive your lens I will inspect it carefully and send you a report of any issues or problems I find, just so we both know where we are before I begin work. Little things like loose screws, misadjustments, or bent filter rings I may offer to fix (no charge) if you agree. I'm not looking for lens repair work, so I'm not going to find big "problems" which you should pay me lots extra to "fix". Of course I will tell you if I see a big problem so you can decide whether you wish to proceed with the modification.NOTE: AI vs. AI-S. Occasionally I get a request to mill the straight round-bottom notch in the lens mount that AI-S lenses have. My equipment is capable of doing that, but I won't. Milling that "divot", as I call it, won't convert it to AI-S. The divot only tells the very few camera bodies which care that it is an AI-S lens. The internal aperture mechanism is what makes it an AI-S lens -- it guarantees a linear response of the little aperture control lever on the back of the lens so that the camera knows what the actual aperture is by how far it moves that lever. Older lenses may not have a linear response, so cutting that divot will only fool the camera into making an incorrect exposure. But this actually only applies to a few film cameras from the early '80s, like the FA, FG, N2000/F301, and N2020/F501. And even they worked fine with AI or AI-converted lenses. AI-S only enabled shutter-priority and some program modes to work better. So in summary: You can't convert a lens to AI-S, and you don't need to anyway.NON-NIKKOR / AFTERMARKET LENSES: Every so often I get a request to modify someone's favorite old Vivitar/Tokina/whatever lens. Most lenses made by manufacturers other than Nikon to fit Nikon cameras do not qualify for this modification. In fact, I have never seen one which does. The aperture ring does not extend behind the lens mount surface, so there is nothing to cut to form the AI ridge. It may be possible to modify these lenses by adding a bit of metal to the edge of the ring, but I do not offer this service.About return shipping: of course it depends on the weight of the lens and distance traveled. I had to put a weight and service because eBay requires it. It will cover most lenses for conversion; many are less and a few are more. I charge actual shipping for UPS or USPS options. Most lenses are only $5 - $10. Winning bidder please tell me which lens(es) you are sending and I will send an eBay invoice for the total. You may ask in advance of bidding if you want to factor shipping cost into your purchase decision.DISCOUNTS: I offer a discount for multiple lenses in one order. For two lenses I provide FREE (domestic) return shipping. Additional lenses over two are $32 each. You can get an even better price if you are handy with small tools and want to remove the aperture ring yourself and send it alone. Ask for details and instructions.International buyers: shipping can be expensive, but you should not have a problem with Customs duties and taxes since you already own your lens. I am careful to mark the Customs form as "Returned Merchandise". Also, consider removing the ring yourself as noted in the previous paragraph -- very inexpensive to send, and no risk of shipping damage to your lens.It is my intention to provide turnaround time no longer than 4 days, but don't hold me to a strict schedule. Occasionally, business trips or personal events may cause a small delay.So take advantage of great prices on those wonderful older lenses! There's a bunch of superb glass available for low prices on eBay which can be used on all the newer cameras with this inexpensive modification.