Repair: Micro-Nikkor 105mm f/4 Ai

Hello, everybody! I’m not feeling well today so I’m going to keep this short. I hate winters because it can get too cold for me to do anything at home. I’m not as robust as I used to. I was almost immune to sickness but it looks like my body is telling me that I am officially a middle-aged person. Ob the topic of toughness, I will show you guys today a very tough Nikkor that was made a long time ago but is still worth looking at these days. Read on.


Today, I will introduce to you the Micro-Nikkor 105mm f/4 Ai lens! This fine lens debuted in the mid ’70s and it’s the first lens of its class. Back then, macro lenses needed a bellows unit for you to zoom in or out. This lens changed it all by incorporating the 105/4 bellows Nikkor lens to a real focusing unit so you can enjoy using this lens like any normal lens. It was very popular and Nikon took a long time to make a successor to this lens because it’s just so good. This lens is a favorite amongst flower photographers and if you just do a bit of searching online you will find lots of people still using this lens. The lens went though a couple of versions but the optics remained the same.

IMG_2439The Micro-Nikkor 105mm f/4 Ai lens only goes down to 1:2 magnification on its own. The Nikon PN-11 extension tube is needed in order for this lens to achieve 1:1 magnification, that’s why there’s a “PN” engraved on the focusing scale. It displays your magnification ratio when you mate it with this lens. This is a very well-made lens. It’s heavy and it’s not flimsy in any way! There’s no plastic parts used in or out of the lens and this will last you more than a lifetime if you took care of yours.IMG_2471The Micro-Nikkor 105mm f/2.8 Ai-S lens replaced this in the catalogue and it’s smaller and lighter. The optics have become a lot more complicated and CRC was also implemented. I will say that the most important improvement is the brighter maximum aperture of f/2.8. This is important because as you extend your lens for higher magnification, the light that is reaching the mirror, sensor or film is also impacted. This will give you a loss of a stop’s worth of light or even more if you have any extension tubes in your setup. This will give you a dark viewfinder and it can be difficult to precisely focus on your subject. Many will say that the Micro-Nikkor 105mm f/4 Ai is sharper and I think that’s true as well but it’s a difficult task to focus on your subject due to a dark viewfinder then this is near pointless.

IMG_2525The Micro-Nikkor 55mm f/2.8 Ai-S lens is a very good companion to this lens. They’re both Micro-Nikkors and their focal lengths compliment each other. They have different uses, I would say that if you are shooting bugs, flowers and other things where natural lighting and keeping your distance from the subject are important then you will want something that’s a little longer. The shorter focal length is great for duplication, documentation and its wider FOV is great for food photography and other types of photography where you’ll want the subject to not look so tiny because using a longer lens will compress your frame and make your subjects appear smaller.

IMG_7240.jpgThis is how long the setup can be when fully extended and with the hood deployed. It has a built-in hood which is very useful. Add some extension tubes to this setup and you will end up with a long and heavy setup.

The key to this lens’ optical performance is the very simple 5 elements in 3 groups optical design. Less is more in lens design and the simpler the lens design, the better. This is true in most cases but there are times when you would need more elements to correct for the optical flaws of a lens. Check out my samples below to see what I mean.

HAW_1231It can be a bit hard to focus on moving subjects with an f/4 lens but here’s a sample of the lens when used for general photography. The high-resolution of this lens is great and this will not be out-resolved by high MP cameras. If somebody tells you that a lens cannot or won’t be out-resolved by any sensor or film then tell them that they’re dreaming.

(Click to enlarge)

This lens seems pretty resistant to ghosts when shot with a strong light source within the frame. There is only a small ghost and you can find it around the 3rd quadrant. It’s really small and I initially thought that it was a leaf on the branch of the tree. This is due to the simple optical construction of this lens. Simple is best and less is more in lens design. The beautiful sun stars look gorgeous and will be very welcome for shooting shiny objects.

HAW_1236While ghosting isn’t much of an issue, flare-resistance is terrible with this lens! Stopping this down will not help much and I had the hood deployed here. This could be due to the poorer coatings used on this lens. I wonder if this is also the case for film because film is less-reflective. I know that the sensors’ shiny surface impacts a lens’ ghost-resistance but maybe it also affects flaring? I don’t think this is the case but who knows? The good news is this lens is sharp despite the terrible flare. If you can just zoom-in on what’s in-focus, it is obvious that the result is sharp despite the loss in contrast due to the flare.

(Click to enlarge)

Here are some more samples of the lens used to shoot more practical shots. Bokeh is nice at this magnification as expected from a macro lens. There’s just a little hint of chromatic aberration wide-open but it’s not something to get worried about.

HAW_1245Here is another sample. Notice how sharp the lens is and how the background melts into a wash of colors? I like it (and so should you)!

HAW_1243Here’s a 1:1 crop from the Nikon Df. See how nice and sharp things are? You can also find some hints of magenta casting on the bloom but that goes away when you stop-down. On the Nikon D750, this lens performed just as great despite the higher megapixel count.

(Click to enlarge)

These samples were shot from f/4, f/5.6 and f/8 respectively. It’s already sharp at f/4 and it is near its peak resolution at f/5.6. At f/8, this lens is able to give you a good balance when it comes to speed and sharpness. I do not have any samples here but diffraction starts to affect the image at about f/16. I shot the last set with the twigs to show you how this lens performs when given a background like this where it’s easier to show ugly bokeh and it’s expected that this lens failed a bit here but that’s to be expected. The positive side is this lens is very sharp as you can see from the samples. The center doesn’t really change a lot as you stop the lens down and the field is reasonably flat.

HAW_1252Here’s a 1:1 crop wide-open. Great details! You can see the very fine details at the center!

HAW_1256Here’s another sample of a picture with plenty of twigs. There’s a bit of vignetting when you shoot this lens at f/4 so if you’re bothered with it then shoot this lens at f/8. Again, pay attention at the “double-line bokeh”.

That’s it for the introduction. I hope that you consider this for your macro photography. I love this lens despite its shortcomings because this lens certainly delivers and it’s cheap. It’s a popular lens for older macro photographers because this lens was popular. Let’s go to the lens repair section shortly after this.

Before We Begin:

If this is the first attempt at opening a lens then I suggest that you read my previous posts regarding screws & driversgrease and other things. Also read regarding the tools that you will need in order to fix your Nikkors.

I highly suggest that you read these primers before you begin (for beginners):

Reading these primers should lessen the chance of ruining your lens if you are a beginner. Also before opening up any lens, always look for other people who have done so in Youtube and the internet. Information is scarce, vague and scattered (that is why I started this) but you can still find some information if you search carefully.

I highly recommend that you also read my working with helicoids post because this is very important and getting it wrong can ruin your day. If I can force you to read this, I would. It is that important!

For more advanced topics, you can read my fungus removal post as a start. This post has a lot of useful information here and there and it will be beneficial for you to read this.

About Me:

I am a photographer based in Tokyo who scours the junk section of the camera shops here on a regular basis. I started this hobby of fixing old lenses and cameras because I kept on getting scammed before when I purchase online. This turned out to be a blessing because I now buy junk lenses for a fraction of the price and then fix them to add to my now-growing collection. This allowed me to buy gear that were otherwise off-limits to me if I were to get them in better condition.

I was a scale modeller before who built models for other collectors for a very longtime, got an education as a dental prosthodontist (but didn’t pursue dentistry) and growing up in a watch repair shop gave me the useful skills that would help me in this craft. Fixing my car also contributed some know-how.

Having mentioned the above, I will tell you now that I am not a professional repairman! So please take what I do with a grain of salt and I will never be held responsible for anything wrong that will happen to you and your project. I hope that the pros would guide and teach us but nobody is writing anything.

As my collection of repair notes grew, I get requests from people with similar interests and from professionals who just needed some notes just in case. Now, I am sharing my library with you for your entertainment and reference. I hope that you find my work useful.


Taking the lens barrel apart isn’t difficult for this lens if you’re experienced with working with manual focus Nikkors. The one impression that stuck with me when I was working with this was the amount of adhesives and thread-locking compound used on this lens. It can pretty annoying really quick so I am warning you now. Having said that, this lens is probably the easiest 105mm Micro-Nikkor around when it comes to overhauling.

IMG_2440First, remove the rubber grip by running a blunt and rounded peg like a toothpick under its whole circumference to lift it from the glue and be careful not to tear it in any way.

IMG_2441The front part of the lens is secured by a tiny grub screw. Rotate the hood until the hole is atop the grub screw. Carefully unscrew it with a precision screwdriver. The grub screw’s slot can be delicate and brittle so be careful. If it doesn’t move, use a bit of solvent.

IMG_2442The front part should be safe to unscrew now that the grub screw is gone. See that small depression on the thread? That’s where the grub screw should sit when you reassemble the lens later on. If it’s not placed properly into the depression then you may break that little thing or it may not get in properly.

IMG_2466The front part comes in 3 parts. It includes the front ring, front bezel and hood.

IMG_2443The front part of the lens consists of the front ring and the hood. The front ring is used to secure objective so it doesn’t fall off. You can now safely pull the objective from the barrel of the lens. Note that the screw near the tip of the housing of the objective should line-up with the slot on the lens barrel. It’s just a guide so the objective doesn’t rotate.

Once the objective is extracted, store it in a safe place so that it will not be damaged while you work on the rest of the lens. Make sure that it doesn’t roll-off the edge of your table!

IMG_2444Next, with the focusing ring rotated all the way to infinity, unscrew 3 of these screws and take note of the focusing ring’s orientation in relation to these screws. These screws are precision adjustment points and it’s used for calibrating the lens’ focus. These screws are secured with lacquer. The lacquer also helps Nikon determine if somebody worked on it.

IMG_2445The focusing ring can now be safely removed. Note that I marked some lines on the main helicoid and the inner helicoid’s walls as a reminder that these lines should line-up later when I reassemble the lens. It doesn’t have to be big or deep but it has to be visible to you or else it’s pointless. You can use anything to make your marks, a screwdriver is also OK.

IMG_2447Now, on to the back of the lens! You can remove the bayonet mount by unscrewing these 5 screws. To make sure that you don’t mess this up, read my article regarding screws and how to remove them. I hope that my readers read my fundamentals and if you haven’t, it is now time for you to read them! I don’t spend a lot of time reminding everybody about how important these are just for the sake of fun!

IMG_2448The bayonet mount can now be safely extracted. Be careful not to damage anything like that spring for the stop-down lever mechanism.

IMG_2449The aperture ring can be removed after you have unscrewed these 2 screws. These little screws secure the aperture fork to the aperture ring. Be careful while removing these, it can be a delicate job because these screws can get rusty and brittle from sweat and oil.

IMG_2450You can now safely remove the aperture ring. The aperture fork’s screw holes are lined with a white substance. That thing is dried-up thread lock and that makes removing the screws a bit more difficult. If you want to be safe then heat these screws with a soldering iron to soften these things before you attempt to unscrew them. Notice that the inner slot is lubricated. This is too much grease and when you reassemble your lens later make it a point to only lubricate this with a very thin film of grease. This part links to the iris and it is not a good idea to oil something that’s connected to the iris in one way or the other as any oil on it can migrate to the iris. This has to be lubricated because it’s long and if you left this dry then this will squeak as you focus in or out. It’s metal-to-metal contact and it will make your lens give out a slight but very annoying sound.

IMG_2451To remove the sleeve and the grip, carefully unscrew the 3 screws on the grip. Make sure that the tip of your screwdriver is not too big or it may scar the grip.

IMG_2452The helicoid key is secured by these 4 big screws. These are all tough to remove and I will advise you to heat these up really well before you attempt to remove any of them. If they are still stuck despite applying heat then use MEK on them and leave it overnight. You’ll have to do it several times because MEK evaporates rather quick.

IMG_2454Here is the helicoid key, notice the white stuff inside the screw holes? The helicoid key is used to keep the helicoids moving in-sync. This helicoid key is very long because it needs to cover the length of the helicoids when fully-extened and this lens extends a lot.

IMG_2455Before you begin separating the helicoids, you will need to remove this actuating rod for the iris assembly. Notice how long it is? It’s long for the same reason as the helicoid key.

IMG_2456The assembly is secured by these 2 screws. Just like the screws on the helicoid key, these are tough to remove and I will do the same for these before I attempt removing them.

IMG_2467You can carefully remove this part by unscrewing these.

IMG_2457Now that all of the things that get in the way are gone, it’s now possible to separate all of the helicoids. Begin with the central helicoid. Carefully remove it and mark where they separated. If you forgot to separate yours then you only have yourself to blame. Read my article on how to work with helicoids if you are new to this.

IMG_2458Oops, I forgot to remove this thing!

IMG_2459The inner helicoid can’t be separated from the central helicoid because the helicoid stop is in the way. It can be easily removed by unscrewing the 2 screws. Notice that I made a mark just in case.

IMG_2460The inner and central helicoids can now be separated. Notice that I made small marks to remind me where they separated. This is very important because this is also the where I will have to mate them in order for them to mesh together properly.

IMG_2462These 3 grub screws secure the adjuster ring to the central helicoid. The adjuster ring is used to adjust the lens’ focusing range and it also serves as the attachment point for the focusing ring. This thing is usually glued and it can be very tricky to remove. The screws are also glued at times and old grease has fused them to the surrounding metal. You can just leave this alone if you want but since I want to remove the old grease and oil that on the inner surface of this thing then I have no choice but to remove this. I would usually soak this in an alcohol bath just to soften the glue or old grease before I attempt to work on it. It usually takes several hours to whole day and it’s better just to be patient than end up with a botched job.

That’s it for the lens barrel. The helicoids are very prominent in this lens’ construction so pay attention when you clean them and make sure that they are smooth. Remove old and dried grease with a toothpick and brush them carefully with a stiff-bristled brush. If you got it right then you will enjoy how smooth the focusing feels.


The objective is not difficult to take apart on this lens and there are only a few number of lens elements to clean. I won’t be showing you how to open the iris mechanism because I have a clean one. If yours is oily then this guide will not help you open your iris to clean it. Unfortunately, I think this lens can be prone to the oily iris problem because of the iris mechanism’s proximity to some oily parts. Just be sure not to lubricate this too much and you’ll be OK.

IMG_2463The rear baffle and the rotating collar can be easily removed with your barehands. Don’t lubricate the collar later as it doesn’t need to be oiled. The collar links to the iris and any oil on this has the potential to migrate to the iris mechanism and cause a bigger problem.

IMG_2464The front elements assembly can be easily unscrewed from the objective’s housing.

IMG_2465You can carefully unscrew this collar with your hands. It houses a lens element in it so be careful not to scratch the glass!

That’s it for the objective. You shouldn’t be spending plenty of time with this because it’s a simple design. This is nowhere near the complexity of the Micro-Nikkor 105mm f/2.8 Ai-S so don’t worry.


That’s it for this lens. Make sure that you calibrate the lens’ infinity focusing and if you’re not familiar with how to do it then you can read my guide for infinity focus calibration. It is a great lens to work on for a lazy weekend’s afternoon. I had no trouble working on it because I’m experienced with working on Nikkors. If you’re a beginner, this is still within your skill so long as you have the correct tools and if you just follow my guide carefully. I will remind you to read my lens repair fundamentals just in case you haven’t because its screws are nearly all secured with glue. There are people who would tell you that it’s OK to use any type of screwdriver for this kind of job, don’t listen to them. People like those are the reason why people end up with a ruined job. There the right way to do it and I’m trying my best to show you how. Thank you very much for following me. This is my last post for 2017 and we will look forward to a wonderful 2018! See you guys again and have a very happy new year! Peace and prosperity to everybody! Ric.

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Maintaining this blog requires money to operate. If you think that this site has helped you or you want to show your support by helping with the upkeep of this site, you can simple make a small donation to my account ( Money is not my prime motivation for this blog and I believe that I have enough to run this but you can help me make this site (and the companion facebook page) grow.

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Thank you very much for your continued support!


Helping support this site will ensure that this will be kept going as long as I have the time and energy for this. I would appreciate it if you just leave out your name or details like your country and other information so that the donations will totally be anonymous it is at all possible. This is a labor of love and I intend to keep it that way for as long as I can. Ric.


1 Comment (+add yours?)

  1. Trackback: World of F-mount Nikkors (2/3) | Richard Haw's Nikon Maintenance Site

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