Repair: Auto-Nikkor-P 105mm f/2.5

Hello, everybody! I am currently very tired and stressed from work and all this repairs and camera blogging thing that is a huge part of my life. We all strive to perfect ourselves with practice and research. Nobody is born a master and we must all pass through these hardships in order to reach our goal. While we can argue that nothing is perfect, we can all agree that there are many in our universe which we can consider to be near-perfect. I know of one Nikkor lens family that can claim to be near perfect and that is our subject this week on this blog, a lens family so perfect that it has become a timeless classic!


Today, I am going to introduce to you the amazing Auto-NIkkor-P 105mm f/2.5 lens! This lens is spectacular and it is one of my favourite lenses! I do not know why it took me so long to write this article. One reader messaged me requesting for an article to guide him on how to fix his lens (a later one) and clean the oily iris. While this is not the same lens for that, I feel that I need to write about this before we go to that particular lens so it will make things easier to read and comprehend for our viewers who aren’t familiar with the 105/2.5 lens family.

IMG_0733Look at that beautiful piece of optical glass! This is one of the legendary Nikkors of old so if you are into collecting Nikkors then I assume that you already own of these lenses in your collection! If not, then you should go out and buy one!

IMG_4257.JPGThis lens first appeared as a lens for the Nikon S series of rangefinder cameras. The lens was designed by no other than the genius lens-god Wakimoto Zenji himself! The optical formula has largely remained the same (Sonnar-type) between these 2 versions except that the F-mount versions had their rear element shortened by about 1mm in order to accommodate the reflex mirror of the Nikon F. The performance remained largely the same according to the 1001 nights articles of Nikon so you can take it as official. I had the chance to overhaul both versions and I can tell you myself that this is indeed the case.

IMG_4256This lens family ran from around 1953-2005 where it finally ended production. In the pic above, you can see the major cosmetic variants of this lens family. Although there’s many minor variations in between these such as having different iris blades number and other smaller details, this is basically it. The only lens I am missing here is the rarer “tickmark” version of this lens. While it resembles the one in this article, it is not identical in many ways cosmetically since the position of the screws and construction is different. Maybe I will get lucky soon and find one for a bargain!

(Click to enlarge)

The lens looks OK externally but closer inspection reveals that this lens has an oily iris so this has to be fixed! Oily irises are merely a symptom of a much larger problem and it is prudent that you should overhaul the lens when you see it.

The video above shows what an oily iris can do. A clean iris will snap shut as soon as you have actuated the stop-down lever but an oily one will retard a bit because oil is slowing the iris down. It should be really snappy on a clean iris mechanism. Please ignore what is playing in the background, I live on a small home and I share the same floor/room with the rest of my family.

IMG_1705Here it is together now with its sibling! The later one has a different aperture ring. These were made with many small variations so collectors love this lens line! There are some small differences between the two such as the position of the screws and the height of the grip but in general, you can think of them as the same lens. By the way, this lens also comes in cm (10.5cm) for the earlier ones.

 (Click pictures to enlarge)

Here are some sample pics from around the minimum focusing distance to around the 2-3m mark. You can see how good this lens is at these distances. The aperture was set to its widest (f/2.5) here to show you how the bokeh is. This lens is very SHARP wide-open and the rendering is exquisite! While modern lenses will certainly out-do this when it comes to sharpness, I can say that very few lenses will come close to this when it comes to the way it renders images. The latest Nikkor 105mm f/1.4E lens can definitely top this but for less than 1/10 of the price, this old lens from the early ’60s is hard to beat! If you are still unconvinced, the most famous example this lens family has ever made is no other than the famous “Afghan Girl” photo. It used the later version with a different optical design but I still bunch them up since they perform very similarly as far as I can see.

(Click pictures to enlarge)

Here are some pictures shot from the mid to the far ranges of the lens, around the 4-40m mark. For me, these are the distances where this lens is unique. This family of lenses is exceptional at these middle distances because these lenses (the 105/2.5 family) can still give you great subject isolation at these distances (specially below 5m). You can literally focus on a subject that is 20m away and still get the foreground blurred a bit (f/2.5) and the transition will still be smooth between what is in focus and what is on the other end of the range. Sure, there will me many lenses in this range that can do exactly this but in my opinion – this lens is hard to beat specially if you consider the price and performance factors. It it sad that Nikon did not continue this lens line beyond the Ai-S version.

Shooting this lens at infinity doesn’t make much sense to me so I don’t know much about how it performs at that range but I suspect that this lens should perform great when you shoot it from f/5.6 to f/8. I believe that this is not the lens for that but of course, this is just me and many people will have a use for it in landscape photography.

IMG_4258.JPGThe optical formula largely remained untouched until the introduction of the P.C. (coated version) in the early ’70s. The optical formula was perfected by Wakimoto Zenji’s prodigy and the original design, the “Sonnar-type” design was modified to a “Xenotar-type” design that’s widely known now as the “Gauss” version. The later “Gauss” version can easily be identified by the difference in lens barrel design but most importantly, you can identify which one is which by simply looking at the rear element.

The earlier “Sonnar-type” has a smaller rear element when compared to the later “Gauss” version. The coating is also not the same as you can see from the picture above.

Both versions render images almost identically but there are some subtle differences if you care to look for them and I will write an article about that in the near the future. I’ll tell you now that there is not much difference between the output of the 2 so don’t worry.

Let’s now start with the teardown!!!

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 growing now 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.

Dismantling (Lens Barrel):

This lens to me is very easy simply because I know this lens in and out very well. Just like the Micro-Nikkor 55mm f/3.5 series of lenses, I have opened and overhauled these lenses more times than I can remember. This lens is simple to service and can be worked on by a novice who has become proficient or familiar with the basic skills needed to service a lens such as working with screws and helicoids. The construction is simple but you will have to be careful with the order in which you remove the components, so pay attention!

Just like most small Nikkor primes in this size and category, you need to first separate the objective so that you can safely work on the lens barrel without worrying about ruining the glass accidentally. This step is easy but you must pay attention and not drop anything to the floor! Again, use the right tools! I always say this but nobody listens.

If all you want is to clean one or two elements then you do not need to open the lens like this just to access the said elements but use your common sense and study how you can get to those elements without having to do this. The minimum that you need to do is to get the objective out of the lens barrel.

IMG_1664First, remove these 3 screws from the focusing ring. These screws hold it in place and be sure to use a screwdriver that properly fits the slot on the screw to prevent damaging it. The screws are so prominent and it would be a shame to see these scarred or stripped.

IMG_1665The focusing ring can come off once the screws are gone. Be careful not to damage that nice chrome sleeve as you pull the focusing ring off the lens, it is easily scratched.

IMG_1666Now that the focusing ring is gone, this tiny set screw can now be accessed. Use a smaller precision screwdriver for this. These screws are easily damaged so be careful.

IMG_1667Once the screw is gone, you can remove the front barrel by unscrewing it from the lens. I left my set screw in place for now but I will store it somewhere safe later. Notice the hole inside the circle. The set screw sinks into it and this is how it secures the front barrel to the rest of the lens. When you reassemble the lens, make sure that the set screw is placed properly into the hole or else your lens will not focus properly or it will seem rough. Also do not over-tighten this screw, you may damage it or the front ring will be offset a bit.

IMG_1668Next, remove the 3 screws that secures the aluminium grip/sleeve. Again, be careful not to damage these screws because they are a very prominent feature of the lens.

IMG_1669The sleeve should come off easily. notice the oil and gunk underneath it.

IMG_1670The moment I saw these marks, I knew that somebody had been here before. These were made by the repairman who worked on this previously and these marks just shows how these parts should align when the lens is collapsed and focused all the way to infinity. It’s very important to make these marks as reference so you will know how things should be when you reassemble you lens later. As much as possible, work on a lens while it’s in the configuration above (infinity) so that you will have a clear point of reference.

IMG_1672You can do this before the previous step and maybe you should! Carefully remove these screws from the lens so you can pull the objective off from the lens. Never do this while the lens is pointed down or the objective will free-fall to the floor! You will have to focus the lens closer to reveal these screws.

IMG_1674Be careful about the objective’s orientation as you pull it out from the lens barrel. Once it is gone, you should focus your lens back to infinity.

IMG_1675Before you remove the aperture ring, remove the screw found on the other side of all the numbers first. That big screw serves as a pin to connect the aperture ring to the aperture fork mechanism found inside the lens. Sorry, but I do not have a picture of that screw but it should be easy to locate since it is the only big screw found on the aperture ring.

IMG_1676Now that the aperture ring is gone you can now access these screws securing the bayonet mount. Use a screwdriver that fits into the hole because if you used a driver that’s even a a small fraction of a millimeter larger then it can ruin the threads surrounding the screw hole. You should also flush it out with naphtha or benzine to reveal the screws’ heads so you can properly fit the drivers to the slots. There is lots of gunk in here so be prepared.

IMG_1678The bayonet mount/plate should come off just like this. Remember, do not force your way or you will damage this part. There is also a spring connecting the stop-down mechanism and be careful not to pull this part too far or it will overextend the spring. if the spring is damaged then it holds no tension, a useless spring by any account. Use a sharp tweezer to remove the spring first before you can totally separate this from the rest of the barrel.

IMG_1680Now, it is finally time to separate the helicoids! Remove these 2 flat-headed screws to free the helicoid key. The helicoid key keeps the helicoids in sync as you rotate the central one and makes it possible for you to achieve focus as it goes up and down the slot. Just make sure that you use the correct-fitting drivers for these because it is going to be trouble just trying to remove these after you have stripped the head.

IMG_1681Here is the helicoid key once it has been extracted. You will have to clean this thing really well before you reinstall it. Always clean away all signs of the old grease before you put them beck together or else it will just contaminate the fresh grease.

IMG_1682Now, this is where the central helicoid and outer helicoid separated. Notice that the guy who worked on this previously really loves to make marks, which is great but he was too enthusiastic and these could have been more discreet. It was convenient,though.

Never forget to do these marks so you will know how these things should mate later. You will have a terrible time figuring this one out if you do note take notes, you don’t need to make your marks as big as the the one in my picture, though.

IMG_1684Next, separate the central helicoid and the inner helicoid. Again, there were marks made ready for me by the person who worked on this previously and they were unnecessarily big again! This guy sure doesn’t want to miss anything!

IMG_1685Now that the outer helicoid is free from everything, you can now access what’s inside the barrel. This rotation ring and aperture fork part simply screws off when you turn it to the left (counter-clockwise). Notice the hole on the retention ring, that hole is where a screw from the aperture ring connects. It serves as a pin for the 2 to work in sync.

IMG_1686And here it is, be careful when handling this so you will not damage the delicate threads on the rotation ring. I once accidentally damaged mine in one of my lenses and it was a terrible experience just to make it work smoothly again! It involved plenty of careful and precise sanding with a very find sandpaper.

Dismantling (Objective):

Now, we can finally work on the objective! This lens is prone to the oily iris syndrome so I advise you to hold back the use of grease for this lens. If your iris is oily, then there is no better way to clean it but to open it up and clean it the proper way. Short-cuts are OK but if you got this far, why won’t you just go the extra mile to ensure that you made a proper job? The iris is being controlled by a series of rotation rings and plates and those needs to be cleaned as well. If oil got it’s way to the iris blades then you can bet that oil also has contaminated these parts. If these parts are not clean you will get an uneven and rough feeling aperture mechanism every time you turn the aperture ring. I got lazy once with a Nikkor-H 50mm f/2 lens and I ended up opening up the lens again just to clean the iris. So that was a lesson for me to learn.

It is also safe to say that the construction of the objective is very similar to other Nikkors of the time so there aren’t any surprises or clever gimmicks used on the objective. All we need to be careful about is the huge chunk of glass in the front elements cell. If you really have to remove the heavy glass doublet (2nd&3rd elements) then push it from front and go slowly at it. This part is usually very snuggly fit so that it creates a vacuum if you did not remove the front element. Also be careful not to damage the cementing in any way.

IMG_1689The rear assembly can be removed simply by unscrewing it with your barehands. If it’ll not move at all, simply drop a a small amount of acetone or alcohol on the seam and let capillary action take the solvent into the thread. Never flood the seam with solvent!!!

The screws (encircled) secures part of the iris mechanism, you don’t have to remove them now just like in the picture. I don’t know what I was thinking that time but it is what it is!

IMG_1703The front elements cell can be unscrewed from the objective’s casing. Notice all the glue in the exterior of the assembly’s casing? If yours won’t budge a bit then it was glued, simply do the alcohol routine again and let the solvent work on the glue before you try again.

Store this big and heavy part somewhere safe where there is no danger of it rolling off or getting damaged from anything.

IMG_1690The rear plate of the objective can be unscrewed just like this. If it won’t move, just use a pair of rubber gloves for extra grip.

IMG_1691Remember the screws I showed a few steps back? Those 3 screws hold this part in place. I made a mark to make sure that the orientation of this part is correct once I put the part back again during reassembly. Notice that the front element cell is still attached in the pic above so please ignore this from now on since you removed it a few steps back.

IMG_1693Here is another view of the iris mechanism before I dismantle it. Be sure to take plenty of  notes before you take apart anything. I highlighted how the spring should be here in the picture above. Remember this when it’s time to put this back together. This part is easily damaged so be careful! This ring fits tightly because Nikon’s tolerances are a bit low and the quality control is very high. I will tell you that other manufacturers are sloppier or a bit more forgiving when it comes to quality control. This is why I love Nikkors!

IMG_1696The ring was pried out of the casing using my fingertips. it can be a really snug fit so use some force but don’t lose too much of it or else you will send this flying into pieces! I do not recommend using any tools for this because you may accidentally damage the blades underneath it. As far as automatic irises go, a damaged blade will make the iris useless.

IMG_1698To further dismantle the iris, you must first remove this tall-headed screw (pillar screw). This part connects to the aperture fork so it can move the iris to move the limiter inside.

IMG_1699Now that the pillar screw is gone, you can just pull this brass rotation ring from the iris assembly. This part keeps the iris assembly from falling apart so do this with the objective facing down to prevent the iris from falling into the floor!

IMG_1700Here it is, the moment of truth! There is no going back after this!

IMG_1701Simply remove the rotation plate by pressing on it’s tab from outside the casing. The tab is the silver part on the 6 o’clock position in the picture. The tab is connected to the stop-down mechanism on the bayonet mount and it actuates this part so that it will open and close as you press the shutter button. This part should never be greased and if you think you need to lubricate yours then use only pure graphite to do so but do not put too much of it. To be frank, this thing is designed to work without lubrication.

The rotation plate has slots in it for each iris blade so rotating it will open or close the iris as the pins on the iris travel up and down the slots on rotation plate. You try doing it for yourself just to see how this mechanism works.

IMG_1702And this is our oily iris! Notice how a small amount of oil is enough to retard the iris and its actuation. I have worked on oilier ones myself. This lens is prone to this problem and I suspect that the oil travels from the stop-down lever and into the iris mechanism. If your lens shows some oil on the blades then it is a symptom of a much bigger problem and it’s best to overhaul the lens rather than just fixing the iris alone.


Whew! That’s another lens saved! As far as I am concerned, this is just a simple routine. I have service this lens numerous times in the past and I still have a few here waiting to be fixed. This lens can be fixed by a beginner if you followed my steps properly but you will have to be very confident with your hands and use the correct tools. It is also advisable to work on cheaper lenses first as practice to get yourself familiar with the skills needed in this craft before you work on a valuable lens such as this. If you think you are not up for this then just leave it to the professionals to do it for you. A properly serviced lens is going to last more than a lifetime so long as you take good care of it by not exposing it to water and dust – things that will surely foul the grease on the lens.

It took me the whole afternoon to work on this but I can work faster if I am not taking all of the pictures for this blog. I am so familiar with this lens now that I rarely take notes at all and I just rely on the small marks that I make as reference.

IMG_1704Here are the blades now! Cleaned the blades individually by wiping the oil away using a lens tissue soaked in naphtha. The iris assembly is simple compared to other lenses but it can be frustrating if this is your first to fix one. Putting back the last blade is always hard so go at it slowly. Be careful when handling the blades so you won’t damage them, a very common form of damage is a bent or warped blade.

To prevent the oil problem from ever happening again, I applied the grease sparingly so I am sure that excess grease will not migrate to places that they are not welcome. It is also very important that you store the lens pointing up so that gravity won’t make the grease migrate towards the middle where the iris is housed. Prevention is always the better way to make sure that your equipment will last you a very long time.

IMG_3889Here are some more Auto-Nikkor-P 105mm f/2.5 lenses. This time, it’s the even earlier one with the rounder 9-bladed iris and cm used instead of mm so Auto-Nikkor-P 10.5cm f/2.5 should be a more accurate name for these. These lenses came from one of our readers, I wish they were mine!

That’s it for this week! Did you enjoy this teardown? For such a popular lens amongst the Nikon user community and beyond, I wonder why I didn’t make this one earlier. This is one of the most requested lenses as far as requests for me to do a teardown goes but it seems that I am too familiar with this lens to write about it. I apologize for that and I will follow your requests even closer in the future. This blog after all is meant to help people save their lenses or at least educate them enough so that they will know if somebody did a botched job on theirs or just conning them out of their extra cash when the job is easy enough to achieve in an hour’s time.

Thank you again for your support! If you enjoyed this article then please share this with your friends on social media so that more and more people will follow this site. I am now hitting almost 14,000 visitors a month and according to a friend, it’s a decent number for a small site that’s maintained by somebody on his free time. Thank you very much, Peter of Nikon Rumors because you are helping this site gain some more exposure. See you all again next time and I will again post something that you will not find anywhere on the net! Please do not get tired of sharing and reading my blog. Love, Ric.

Help Support this Blog:

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.

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.


3 Comments (+add yours?)

  1. Trackback: Internet Nikon Repair Resources – My Take on Photography and Diving (Underwater Photography Mostly)
  2. Trackback: Repair: Auto-Nikkor-P.C. 105mm f/2.5 | Richard Haw's Classic Nikkor Maintenance Site
  3. Trackback: Repair: RF-Nikkor-P.C 105mm f/2.5 | Richard Haw's Classic Nikkor Maintenance Site

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