Repair: RF-Nikkor-P.C 10.5cm f/2.5

Hello, everybody! It is Father’s Day today so I will greet all of the fathers who are reading my blog today a very happy Father’s Day! I was admitted to the hospital today because of my blood pressure but I am OK now but the most important thing is I spent time with my family. I spend so much time at work and maintaining this blog that I often times find I’m neglecting my family. Speaking of fathers, I am going to introduce to you a very special father this time because this father started a long line of excellent descendants!


Today, we are going to talk about the father of this venerable lens family that we started talking about in the previous articles, the RF-Nikkor-P.C 10.5cm f/2.5 lens! This lens made it’s debut in late 1953 and was made to fill-in the gap between 85mm and 135mm. Some people find the focal length odd but it makes a lot of sense if you are carrying a 50mm in your bag because 85mm just isn’t too different from 50mm and 135mm may be too long for many people. The f/2.5 maximum aperture may also be unusual to many people who aren’t familiar with Nikon’s history but the f/2.5 maximum aperture was also used on the W-Nikkor 3.5cm f/2.5 RF lens. Back in the day, Nikon was in a contest with everyone else so even a small lead counts! This was the fastest lens in the 100mm class, imagine that.

IMG_3765This lens looks gorgeous with all those shiny chromed parts. You will sure to get plenty of stares when you shoot with this lens! I know some people who treat cameras as jewelry. I know it sounds weird but who are we to tell them otherwise?

This lens was designed by the legendary Wakimoto Zenji, a giant in the Japanese optical industry and it the predecessor of the famous Nikkor-P 105mm f/2.5 series of lenses. The design was very long-lived and it pretty much stayed that way until the early 1970s when it was given an update by the disciple of Wakimoto Zenji.

sonnarGaussHere is a simple comparison between the original 5-in-3 formula the later 5-in-4 formula. While the formula shown on the left is for the Nikkor-P 105mm f/2.5 lens for the F-mount, the difference is negligible since the rear element was only reduced by about 1mm just to make clearance for the Nikon F’s reflex mirror so you can think of it as the same formula used on this lens if only for the sake of having a visual reference to give you an idea.

The design can be thought of as an enlarged RF-Nikkor-P.C 8.5cm f/2 lens, also designed by Wakimoto Zenji. The original optical design served as a template for this lens and it worked pretty well! I shoot with both lenses and I can say that the characteristics of both lenses are similar in many ways because of the shared “Sonnar-type” lineage.

IMG_3766This lens was sold as junk because of some coating damage by a previous fungus attack. I also noticed that it will not focus all the way to infinity and the shop wasn’t aware of this.

This lens comes in 2 subtle versions and the lens shown in this article is the latter type. It is just updated with a different way of putting on the lens shade where the original one has 2 small lugs to secure the hood and this one has none, resulting in a smoother front barrel that will not snag on anything accidentally. The differences are insignificant that you can almost treat the 2 versions as identical in many ways. This is all I am aware of.

IMG_4257Here it is compared to the F-mount version. They are different in every way but you can consider them to be identical since the optical design wasn’t changed much. Some people claim that the rangefinder version is better because the rear is closer to the film plane so there were a few interesting optical artifacts like the glowing highlights are absent on the F-mount incarnation of the lens. I cannot verify this and I will update you when I do.

IMG_4256Here it is with the rest of the family! From the first one on the left from 1953 all the way to the last one to the right which ended production around the new millennium. If you’re a new Nikon photographer and you don’t know what this lens family is about then I will advise you to read my articles and get to know these better! They are all magnificent.

Second from the left, we have the Nikkor-P 105mm f/2.5 lens and the next one to the right is the updated optical design, the Nikkor-P.C 105mm f/2.5 lens. I will continue writing for the rest of the family when I have the time but for now, all I have written is for the first 3 lenses and maybe a comparison if I really have some time on my hands.

IMG_3807It looks great on my Nikon S3. The 35mm, 50mm and the 105mm is the trinity set for the Nikon S3 because it has frame lines for these 3 focal lengths. Very convenient!

Compared to the other telephoto lenses that Nikon made for the rangefinders, this lens is relatively new that it ever only came in the “new” look of chrome and black. While older telephoto lenses like the RF-Nikkor-Q.C 13.5cm f/3.5 and RF-Nikkor-P.C 13.5cm f/3.5 came in all-chrome first and then the two-tone “panda” version like we see here.

(click to enlarge)

Here are some sample shots that I did as soon as I finished overhauling this lens. The pics have no creative value since I usually shoot a roll to test the lens and see if I got the focus coupled properly to the rangefinder and to see how this lens performs. See how creamy the bokeh is? You can also see that the lens is indeed sharp wide-open and it will improve a lot when you stop it down to f/4. You can also see that large polygonal blob when shot against the sun, this has more to do with the lens’ outdated coating than the design of the optics. A flaw set by the limitations of it’s time.

(click to enlarge)

Now for some colour photographs! Somebody who shot this lens on digital suggested that I shoot this in colour film and so I did! Very nice lens to use with colour film. The results are also full of character as you can see in the transition from what’s in focus to what’s out of focus, very organic and natural. The look is outdated but in a very good way.

I hope that this is a good enough introduction for you. Now, let’s 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’ll find my work useful.

Disassembly (Focusing Unit):

First, we would like to separate the objective from the focusing unit to prevent it from any accidents. This should be standard procedure every time you work on any lens but some will not come off easily just like this. Rangefinder lenses are simpler and so you can just remove it with your bare-hands. It was engineered this way by Nikon so you can change the focusing unit to Contax, Leica or even the Nikon F-mount fit! Nikon sold the F-mount focusing units separately, this much is confirmed by old catalogues but the Contax/Leica fit were definitely sold from the factory as-is. Interesting, huh?

IMG_3767The objective can be easily removed by unscrewing it from the focusing unit. It may take some effort because it may be glued or old lubricant may have bonded it together.

IMG_3768Be careful not to damage or lose this brass shim. It is used as a washer and also to help it focus to infinity. These are pretty much unique to each lens and were selected from a box of spares by the person who’s in-charge of calibrating it’s focus.

IMG_3769Remember that this lens was sold as junk because it will not focus all the way to infinity? Well, this is the cause! I do not know how this thing got inside but it was preventing this lens from collapsing all the way. Don’t ask me where this came from, I want to know,too.

IMG_3770See, now it collapses all the way! I can really make a good living repairing lenses. Maybe I should do it in my retirement? It is a very time-consuming endeavor that’s all.

IMG_3771Remove the focusing ring by unscrewing the 3 screws that secure it to the inner helicoid.

IMG_3772Take note of the position of the screws before you dismantle this lens any further. Taking notes is essential but people just don’t listen and message me when things go wrong.

IMG_3773This screw prevents the helicoids from rotating outside of the lens’ focus range. Carefully remove this as these can be delicate because the neck of the screw is thin!

IMG_3776Again, take notes and pictures before you dismantle! This shows the focusing cam’s inner mechanism. The screw slides within the slot as you focus the lens in and out. The cam on the other side pushes on a lever in the camera that operates the rangefinder. This is how the rangefinder shows you what’s in focus.

IMG_3777This is how much the helicoid will extend before the screw is removed. I took this so I’ll know later if I reassembled it correctly or not. Do these now before you go any further!

IMG_3778Separate the helicoids and never forget to mark where they separated! If you forgot to do this then you will spend plenty of time guessing where these should mate later since you will have to mate them in the same position as where they separated.

IMG_3779This decorative sleeve can be removed after getting rid of the 3 screws holding it down. I believe that this is overkill since the scale can be engraved into the main barrel anyway. I almost always find oil underneath this so maybe this was implemented to somehow help with keeping oil from seeping out of the lens barrel, who knows.

IMG_3781Let’s go to the rear this time. Remove this set screw so you can remove the retainer ring. It is there to secure the ring from accidentally being moved.

IMG_3782The retention ring can be unscrewed by using a lens spanner. Look at the picture and see that there is a groove on the thread. This is where the set screw used to be. Remember to rotate it exactly to how it was before you remove it before you put the set screw back.

IMG_3783Once the ring is gone, you can take out the focusing cam mechanism with your fingers.

IMG_3784To remove the cam’s collar, unscrew this carefully and be sure not to lose it. This screw is in charge of keeping the cam in-place as well as keeping everything together.

IMG_3785Once the screw is gone, everything comes apart. That spring is responsible for pushing it out so it comes into contact with the rangefinder lever all the time.

IMG_3786You can remove the collar on the mount if you wish but it won’t help with anything with regards to repairing this lens apart from removing old junk trapped underneath it.

IMG_3787This is how it comes off. Again, there is no real benefit in removing this.

IMG_3788If your lens doesn’t sit properly to the mount on the body then you can use your hands or a pair of pliers wrapped in rubber to bend these a bit. This is a delicate operation and I’ll advise you not to do this unless you know what you are doing because the problem may not be on the lens but on the flanges on the camera’s mount itself. Just forget about it!

I doubt that many people will have problems with the focusing unit of this lens but there will be people who will want to take it apart due to grease migration or a dry helicoid or worse, a seized helicoid. I make it a habit to do this on all of my lenses because I just do not trust what’s there and I do intend to keep these things forever.

The helicoids have been thoroughly cleaned with naphtha or benzene with an old but clean toothbrush. It was wiped and brushed with a soft pig-hair wheel brush on a Dremel and then wiped some more until the tissue wipes clear of anything. I am very meticulous when it comes to this step because I do not want old grease to contaminate the new one. Use a light grease for this because the internal helicoid on the camera body will add some resistance to the focusing ring. Don’t apply too much grease or you will end up with an oily lens.

The cam on the end and the spring under it were also lightly lubricated with the same grease used on the helicoids. This will prevent it from squeaking. If ever you find any rust on the spring, just clean it off using a fin steel wool or WD40 and be sure to clean it up thoroughly to leave no residues before lubricating it lightly and putting it back to it’s assembly.

Be careful with the Dremel! Only use a very soft organic brush to polish anything related to the threads in your helicoids! A steady hand is needed whether you use it with a drill stand hold it with your hands.

Disassembly (Objective):

The objective is so familiar to me since I have worked on this lens family pretty often. It is simple enough and the elements are huge so handling them is easier. There is nothing I’ll have to warn you about this thing but just the basics, take notes and be careful!

IMG_3789The front elements cell can be removed by unscrewing it from the rest of the objective. It neatly comes off as an assembly as you can see here. Be careful not to scratch the back of this thing as it is exposed and can come in contact with anything inside the casing.

IMG_3790The front (1st) element can be removed by unscrewing the front barrel. This may fall all the way to the ground if you are not careful so do this while it is facing the ceiling.

IMG_3791The front element can now be extracted using a lens sucker.

IMG_3805The 2nd group consisting of the 2nd,3rd and 4th elements (a triplet) comes off when you unscrew the collar securing it on the other end of this assembly. Both ends are accessible without removing it from the case so you can clean it just like this unless there’s fungus or serious “schneideritis” on the sides of this group which very rarely happens.

IMG_3806I am removing this just in case somebody is curious. These are usually snuggly-fit so do not force it or you will risk damaging the glass. Do you want that? Of course not!

IMG_3792The rear and last element (5th) can be accessed and cleaned thoroughly by removing this collar. You may have to place a drop of alcohol to soften the lacquer that Nikon applied to these things to secure them. This rarely happens on really old lenses but who knows?

IMG_3793You can extract it by using a lens sucker. At this point, I will place a dot with a Sharpie to help me identify which side should be facing forward. The curvature of this element is a bit shallow and it can be difficult to tell which side convex or not for some people. I have worked on this lens family long enough to know that this is concave on the surface that’s facing the camera. Just do this as a precaution, a simple permanent marker works well.

That’s it for the elements. People who just want to remove fungus or dirt will only take it apart up to this point. If you are hardcore, continue to the next section!

Dismantling (Iris Assembly):

The iris assembly on rangefinder lenses aren’t as delicate as the ones found on automatic lenses (SLR’s mostly) so having a bit of oil in them is tolerable. I will clean this one just to show you how if it bothers you. The oil will evaporate eventually and it will settle on the surface of the elements and ruin the coating. Of course, this is bad but it’s your call if you want to spend this much effort on cleaning the iris assembly or not. Better having an oily iris then having one named “Humpty-dumpty” since you can’t put it back together again.

IMG_3794Begin by removing this screw but mark the position of the aperture ring first.

IMG_3795The aperture ring is only being held by 3 small set screws. See the dimple on the collar in the picture? That is where the set screws sink into. You must put this ring back together again the same way as how it was so the mark we made in the previous step will help.

IMG_3796Now, remove this brass ring to remove the rotator cup that is securing the iris blades or leaf. You may need a sharp pick for this and it may take you some time to get it out. Once this is gone, everything can fall off so be careful!

IMG_3797If you haven’t unscrewed this then do it now!

IMG_3798Carefully remove the rotator cup with your fingers.

IMG_3800The collar can now be removed by unscrewing it off. Do note the original position of this thing before you remove it. Some people count how many turns it takes to unscrew it but I use measurements and orientation instead. Do whichever you are comfortable with.

IMG_3799See how intricate the iris is? Just seeing this is enough to scare me just thinking about the time and effort it takes to put these things back together. They are more difficult than the ones found o most SLR lenses because there are more of them and they are all overlaying with each other. The good thing is they are usually heavier so they stay will put.

IMG_3801Drop the iris blades into a soft and clean lens tissue and be careful not to warp them. The iris blades are very delicate and a damaged one will result in an irregular-shaped iris or worse, an iris that doesn’t close or open properly!

IMG_3802Carefully wipe the iris blades with a lint-free tissue such as a lens tissue and use naphtha to dissolve the lubricant and help soften any rust that has formed. This one is easy since the blades don’t look symmetrical. The rule is to have the pin on the rounder end of the blade connect to the hole on the housing. The rounder end makes clearance for the iris to move. Putting it back the wrong way will result in an iris that will not stop-down properly. You will know it when you see it!

IMG_3803After al the hard work, here it is! There are many techniques to do this, mine is to slide a blade under the one on top and then push it into place by using a pair of tweezers. Only handle the pins and never the blades itself!

IMG_3804Sorry for the mis-focus but I am sure you can see that the iris is now perfectly installed.

I hope that you got yours back together after this. Don’t worry, it will take a few attempts before you learn how to do this. If you really want to practice how to do this then do it on a cheap Russian rangefinder lens sold as junk for parts. No need to ruin a good lens just for the sake of learning a new skill. Nikkors are family heirlooms!


As far as lenses for the Nikon rangefinder system goes, this is still pretty standard and it has a lot in common with the other telephoto lenses in terms of engineering so I was not even worried about this thing when I worked on mine. In fact, this took me less time to overhaul than expected because there aren’t many parts to take care of. Of course, I am saying this from the point of an experienced Nikkor repair hobbyist. I put the emphasis on Nikkor because I do not trust myself with lenses from another brand.

IMG_4348This is one that comes in metric! Sold this to somebody else but I wish I didn’t because its rarer. I rarely sell my lenses and if I do, I usually sell them to people I know. I may buy it back one day, nobody can tell.

This is a simple lens for somebody who is willing to study the Nikon rangefinder lenses. I would not advise that you ruin one as an experiment because these aren’t cheap like the majority of the F-mount lenses due to their scarcity and age so only attempt doing this if you trust your hands enough to work on delicate objects like these.

The only troublesome part of this lens is the iris and I doubt many people will even try to attempt taking it apart but if ever you have the need to then this is how to properly do it. Some people will just saturate the iris with naphtha and wipe away the gunk but that is not the proper way to do it and the problem will soon come back. I will admit that I also do it sometimes (very rare) and I am ashamed to say so but that is only for the lenses I wasn’t able to open up completely due to the lack of tools are the delicateness of the lens. I would rather have a lens with an oily iris than a lens with a damaged element!

Here we are again at the end of another article. I hope that you liked this one and if you benefitted from this, don’t be shy and donate some to my blog. I’m considering updating this account again and it will be very helpful if you can help me with the upkeep so that I can keep this thing running and also keep the files on another server to help with all that bandwidth because my blog is obviously very picture-heavy. Thank you guys again, 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.


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