Repair: Nikkor-T 10.5cm f/4


Today, we are going to look at the Nikkor-T 10.5cm f4 lens! There is very little information on this lens outside of its history so I hope that I can shed some light into this lens and its characteristics when used in real-life applications. This lens was made when the Nikon F was rocking the charts in the very early ’60s. There’s a rumor that this lens was made for Nikon’s rangefinder cameras but it was also repurposed as an F-mount lens to cut cost. It can be hard to confirm this rumor but it’s easy to see where it came from. It looks goofy and is more in-line with ranegfinder design than a proper F-mount lens. it’s a preset-iris type lens like the Micro-Nikkor 5.5cm f/3.5 and the PC-Nikkor 35mm f/3.5 but unlike these lenses, this lens doesn’t have a real reason for being a preset-type lens. A preset-type lens is where you manually close the iris before shooting because the camera doesn’t do it for you automatically. This weird design and the preset-type aperture are the 2 features that define this lens but there is another thing and that’s “cheapness” and it’s something that many people overlook. You see, this lens was designed to be made as cheap as possible. It was a bad marketing decision because people buy Nikkors for their quality. This lens had a reputation of cheapness that it hurt its own sales and that lead to its very low numbers, making it rare. Fast-forward 50 years and its rarity has made it a collector’s item and the price of this lens has inflated so much that it became a rich man’s toy. Luckily, I was able to find one for cheap. It was sold at a much lower price because of the wear and the old owner made a terrible repair job. It was so bad that even the screws didn’t match! I had to replace the screws with the ones I have in my scraps box! Needless to say, it was a very expensive junk but it has been one of my dreams to introduce this lens to!

IMG_6416The Nikkor-T 10.5cm f4 looks very odd. It’s small and thin but it flares at its base so that it can accommodate the wider throat of the F-mount bayonet. Despite being short, the lens can extend almost 3cm when you focus it to its minimum focusing distance. If you want a lite setup for a leisurely stroll around town then this lens is the one to take with you. It also has a very nice nickname, “Mountain Nikkor”. It got that name because people were linking it to the “Mountain Elmar” of Leica which is an optic that shared a few attributes with this lens. Needless to say, they were both ugly lenses.This lens only has 3 elements. It was popular for lens manufacturers to make 3-element lenses (triplets) for the low-end market and these lenses are usually cheap because they only have 3 elements and their construction is usually revolved around cost-cutting. This was at a time when Nikon was already known for its quality control and performance so this lens was really a misfit. It hurt the company image so much that Nikon stopped this economy-driven nonsense and only did it again in the ’80s with the Series E lenses but it never used the “Nikkor” tradename this time around. There was a magazine article titled “Why Can’t We Sell This Lens” in a Japanese Nikon magazine back then and it detailed its unfortunate sales history and why nobody wanted one back then. The answer was clear, the lens have the overall impression of “cheapness”. It felt like it was made by somebody else and people would just save-up to buy the excellent Auto-Nikkor-P 105mm f/2.5 that’s a lot better and is popular with everybody back then. Needless to say, this poor thing was only sold for a very short time. Branding is very important and this is just one example.

The S-mount version of this lens sold even less because people were transitioning to the Nikon F and there’s also an existing 105/2.5 for the S-mount that it made very little sense to purchase this. Having said that, the S-mount version is even rarer and costs almost 2x the money these days compared to this lens. I hope to find a cheap one in the future.

IMG_6450The lens looks very odd on any camera because it has a thin profile. Even if it’s mounted on a rangefinder camera (S-mount version) it still looks off in some ways. Operating this lens on an SLR with automatic diaphragm action felt weird because you should open and close the iris manually but you will soon get used to it.

Using this lens can be awkward because of its narrow profile and the fact that you have to stop it down manually. If you haven’t shot with Nikon rangefinders the it can feel alien to your hands when you grab this lens because all F-mount lenses are stouter than this.

IMG_6493It sure looks better on the Sony A7. An ugly lens can make a good match for an ugly Sony. Both are ergonomic horror stories and they belong together, a kind of “how to make ugly gear” theme. Operating them together made more sense to be honest because mirrorless cameras don’t benefit much from the automatic iris actuation feature because the finder will brighten up the display anyway when stop this lens down. It’s a feature that’s unique to mirrorless cameras which makes them great for using old non-automatic lenses.

Despite the weird handling, this lens also has equally weird characteristics that I’ll show you in the sample pictures section. This is unique lens in the Nikkor lineup and the next few sets of pictures will show you why it’s unique. It’s not mainstream!

(Click to enlarge)

This lens flares a lot! I don’t know what contributes to this, the only thing I can think of is the coatings (or lack of it). I am sure that it’s coated because mine exhibits a bluish hue so I’m  guessing that it has some form of coating. How good the coatings are is beyond what I know about this lens but my tests shows that it’s near useless. I never saw anything like this even on Nikon’s very early lenses from the rangefinder years and my oldest Nikkor’s made in 1949 or so! Could the very low element count contribute to this? Despite this, it’s obvious that the lens is sharp if you zoom-in on what’s focused.

(Click to enlarge)

If you think the previous set looked ugly then wait until you see this set! It reminds me of my baby’s ultrasound pictures! Just look at that pillar of light! It’s just the sun outside the frame. Look closely and you will notice that the curtain of light doesn’t go past the frame. It looks like it was cut at its source near the edge of the frame. What could that be? I don’t know but I will ask some optical engineers the next time I meet one and I will tell inform you guys. You can use this as an effect if you wish, it certainly looks trippy to me. Maybe I can develop something from this flaw and use it to my creative advantage.

(Click to enlarge)

More samples of the flaring problem but not as bad this time. One thing that can cause it is the shiny metal front ring. I was using this lens without any shade and the reflection is probably the one causing all these ugly artifacts to surface. I don’t have the hood and it is not a common item, I will just be patient and maybe I can find one in the future.

Now that we saw the ugly attributes of this lens, it’s time to balance it by looking at these photos that were shot in real-world scenarios. The lens has a redeeming quality and you can judge it for yourself! Click on each picture and examine them to see what I mean.

(Click to enlarge)

The lens is sharp wide-open! It also has a nice 3D-like effect going on despite only having f/4 as its widest aperture. The very low element count contributes to this, giving it a nice character. Contrast is average wide-open but picks-up bu stopping it down to f/5.6 and it’s starting to look really generic by f/8. I’ll only shoot this lens at f/4 because this is where all the magic is and at f/5.6 if I really need to. The bokeh is so-so but is on the pleasant side. It is nothing special to be honest but you can sttill make good use of it.

HAW_0813As usual, here’s my picture of leaves and twigs because these subjects are great examples for showing bad bokeh. I can see some smudging and “double line bokeh” but it’s not that terrible though the overall impression was “cheap”. The lens is sharp and I think that it’s the most important thing for amateurs (the target market for this lens).

HAW_0840Here’s another sample. Not the best lens for shooting bokeh balls at night to be honest.

HAW_1358The 105mm focal length is good for portraiture. It’s apparent in this picture that f/4 is not what you want if you need to hide an ugly background. I would like to point out that the separation of this lens is very good. See how the subject looks very “3D-like” and how she is separated from the background really well. The details on her cloths look great, too. It was shot at f/4 and I wasn’t expecting much but this exceeded my expectations. The very low element count is what’s giving this picture such a pleasing and organic feel.

HAW_1340Here’s an example of the lens shot at infinity (well, close to it). When I magnify it to 1:1 in my monitor, the details look very sharp and it felt like this shot was taked at f/5.6 despite being shot wide-open. I also can’t sense any visible distortion. Impressive!

(Click to enlarge)

Here are some sample pictures using Fujifilm Superia 100. As usual, it’s more forgiving to shoot with film but I wanted to show these to you because this lens was designed back in the days when all we had was film. Showing these to you gives it a better context and you can appreciate this article better now that you have seen how this lens behaves in digital and film. The results aren’t remarkable but they look decent enough. Also note that this lens doesn’t have a lot of vignetting. I remember stopping the lens down a bit here so that should probably explain the lack of vignetting on the picture to the left but the other one was shot wide-open if I recall it properly. There’s just a hint of vignetting and that’s all.

By the way, Roland Vink has this to say:

“The blades have an odd shape though, the edges have strong curvature so when stopped down a little the opening has a star or saw-tooth shape. Only at smaller apertures or near wide open is the aperture a regular 9-sided polygon.

Since the optical unit is very compact (front to rear) and the focal length is moderately long, there is very little mechanical vignetting so illumination is relatively uniform even wide open. (So this explains the lack of vignetting. Thanks, Roland!)

One nice feature of this lens is the 0.8m close focus limit so it is handy for closeups. This is much closer than the 1.2m limit of the Nikkor-P 105mm f/2.5 Auto from the same time period. It also has a classic Cooke Triplet optical design which is relatively symmetrical so close performance is pretty good.

Flaring is probably due to the simple coatings and the optical design which tends to send reflections onto the image plane rather than elsewhere. The chrome filter ring does not help either, so using the little hood is useful.”

With this introduction, I hope that I gave you a good insight on how to use this lens and if you really want to have it or not. This lens deserves to be used more and not rot inside a cabinet on a collector’s house. I have fallen inlove with this lens and I have learned how to work around its flaws. Is this lens for you? Only you can answer that question! Let’s go on to the main repair article!

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.

Disassembly (Lens Barrel):

The construction of this lens isn’t conventional. On our typical F-mount lenses, we would normally begin by removing the objective of a lens and it’s just a question of where we’ll be opening it from (front or back). This lens doesn’t fall into this pattern and you will see it for yourself soon. This is a nice refreshing experience because truth be told, I’m getting bored at opening the usual Nikkor lenses. For me, this is a nice learning experience and I hope that you will find this just as amusing as I did. I call this lens “Ajahn Lens”. Ajahn is a Thai Buddhist term for teacher and if something taught you a lesson then I think it is a good reason to honor it. Thank you, Ajahn Lens.

IMG_6422Remove the baffle by using a lens spanner or better yet, use a rubber stopper and simply use friction and try to unscrew the baffle. This is safer because rubber will not scratch it.

Take note of the 2 encircled dimples. Those are the slots for the retention ring. You must first remove the baffle before removing the retention ring to prevent damaging the ribs on the baffle. The retention ring is the only thing holding the lens together so remove the retention ring with caution so you won’t drop the front part of the lens.

IMG_6425Here is the baffle. It’s a big piece of milled alloy and it serves as a light seal. It also hides the inner parts of the lens so they’re protected from dust.

IMG_6423Remove the retention so the front part of the lens can be separated from the main barrel.

IMG_6426And make sure not to leave the retention ring inside!

IMG_6419The focusing ring is secured by these 3 screws.

IMG_6424Removing those screws will allow you to remove the focusing ring.

IMG_6430The grip is secured by these grub screws. Carefully remove these with a precision driver and make sure not to scar the surrounding metal. If you observe it carefully, you can see that it’s not aligned to the center. The idiot who worked on this lens made a poor job.

IMG_6431It can be lifted from the throat of the lens just like this. See the actual depression where it should have sunk-in? It was actually trying to dig into the metal and created new marks just beside the proper hole. I know I “khao pek” too much but who won’t!?

IMG_6432The bayonet mount can be removed by unscrewing these 3 screws. Make sure to read my article on working with screws if you’re new to this to prevent any damage.

Very early versions of this lens have a groove for the locking pin. This one doesn’t have it despite being an early model.

IMG_6433The bayonet can now be safely removed. Make sure that you remember it’s orientation. I got a bit confused when I was putting this back together because there aren’t any other features to remind me except for the slot for the locking pin. It should sit exactly at 9:00 on every F-mount lens.

IMG_6435Time to remove the base cover. This covers the screws on the lens and makes it look nice. I doubt that it’s glued so you can just use your hands to unscrew it. If it won’t move, just use some alcohol or solvents to soften the glue before you attempt to remove it.

IMG_6436Removing the cover should reveal these 3 screws. These hold the sleeve to the lens’ base. Mine looked corroded and disgusting. Well, the whole lens was disgusting so I saved it!

IMG_6437The sleeve can now be pulled from the main barrel. Notice that there’s a brass shim. The brass shim looked out-of-place but it’s there. I think it acts more like a gasket to prevent any oil from running out from this place. A more sensible use for it is it’s used as a rail so that the rotating tube under it has a smooth surface to come in contact with.

IMG_6434This screw is there to prevent the lens from focusing past its range. You can remove it or you can just leave it there because it won’t prevent you from separating the lens further. I chose to unscrew it so I can clean it thoroughly.

IMG_6438Curiously, this lens doesn’t even have a proper helicoid and it uses a cam to focus. I know that this lens was made with cost-cutting in mind but this is ridiculous. Cams are used if you want a non-linear extension. This made a lot of sense with the GN-Nikkor 45mm f/2.8 because its focusing can be synced to its iris and it has a non-linear iris. Inverse square is also reason for using a cam because light doesn’t decay in a linear fashion. In this case, it looks like the came method was chosen because it’s cheaper to manufacture.

To separate the telescoping tubes, carefully unscrew this and be careful not to crack that nylon-like thing. I remember that this thing consists of a spindle and that nylon-like thing and to put it back again, you will have to screw the spindle back first before you press-fit that plastic thing back into place. It can be scary to do because this part can easily crack.

IMG_6439Once that thing is gone, you can now separate the sleeve where the focusing ring used to be connected to. Make sure that you don’t misplace that brass ring.

IMG_6440The inner tube can now be removed. This is where the thing that we just removed a few steps back used to be screwed into. Just lightly grease the inner tube’s outer surface. Too much grease will only make this sloppy or hard to focus.

That’s simpler than what I was expecting. The simple construction of this lens shows how Nikon was trying to make a cheap lens by cutting corners where they can. A helicoid will make your focusing smoother but this cam worked just as well and to be honest, I cannot even tell any difference. The only thing that I’ll caution you is to be careful when turning it because that only thing that’s between you and ruining this lens is a small screw and a plastic part. If you over-turn it then this part may break under stress. Seeing the insides of lenses can tell you a lot about how to care for them. Proper care will assure that these lenses will give more decades of fun and not end up being junks (sold for parts).

Disassembly (Front Barrel):

I decided that I will condense the sections for the iris assembly, objective and front barrel into a single part because the lens is simple and I think that it makes more sense this way instead of having them in separate parts which can just confuse you. This is unlike your usual F-mount Nikkor because it’s a preset-type lens and so our usual layout won’t work. Again, use the correct drivers for the job and you should be fine.

IMG_6420This screw comes in contact with another screw inside so the aperture ring will not turn past its range. Remove the screw so you can turn the aperture ring all the way, this will help you position some of the parts inside while you remove it.

IMG_6449This is the screw that it comes into contact with. Don’t bother doing anything to this thing and just leave it be. You can disassemble the lens without removing this thing.

IMG_6421The preset iris ring can be removed by unscrew 3 small set screws around it. Notice that I still have it mounted onto the main barrel in this picture. I did this so that the lens will have something connected to it while I take this picture.

IMG_6428This sleeve can now be removed. It’s just screwed to the front barrel assembly. It’s there to protect the lens from dust and also to make the lens presentable. I am not sure if there is a screw that’s securing this thing but in my sample, I found no screws connected to this part at all. However, there is a hole on one side and what that hole does is unknown.

IMG_6429The preset iris ring can be unscrewed and removed just like this after you have removed all of the screws on it.

IMG_6441The inner ring for the preset iris couples to iris via this screw. Remove this screw so that you remove the ring. This screw can be brittle so be careful when you remove it.

IMG_6442The ring should come off easily once the screw is gone. Please pardon the poor focus.

IMG_6443This bigger screw should be removed in order for you to advace.

IMG_6444Now that the screw is gone, you can now remove this brass spacer.

IMG_6445The rear optical cell can be unscrewed just like this. You should do this earlier, as soon as you have access to this part. I don’t know why I only removed this now but here it is. Put it in nice and secure place so it’s protected from hard and it won’t roll-off the table.

IMG_6446To remove the front element, you simply have to remove the name ring with a spanner. I would advise that you first use a rubber friction cup to remove this part first before you try doing it with a spanner. This is a prominent part of the lens and a metal tool might be able to scratch it if you are not careful. If this is stuck, just place a drop of alcohol and let capillary action do the rest of the job. That will soften any glue that was used here.

IMG_6447You can now remove the name ring.

IMG_6448The front element can be removed by using a lens sucker. Do take note about where this should be facing. It’s obvious that the convex part should be facing forward but I want to warn you in case you’re ignorant about this. Use a Sharpie and draw a small dot on the wall of the lens to remind you where this thing should be facing.

IMG_6467The 2nd element is secured by this collar. Mine was secured with lacquer so I just placed a drop of alcohol onto the hole beside the collar and let the alcohol soften the lacquer. If this won’t work and the collar is still stuck then you should probably use a rubber glove to give you some extra grip. Don’t use a lens spanner on this as it’s not needed.

IMG_6455The 2nd element can now be extracted using a lens sucker. Again, don’t forget to make a small dot on the wall of the element to remind you where this thing should be facing.

IMG_6456The rear element is secured by a collar just like the 2nd element. Repeat what you did to the 2nd element but use a lens spanner this time. Be careful not to scratch the surface of the glass when you do this.

IMG_6451The rear element can now be extracted with a lens sucker. Not the 3 dots that I drew on its wall. These 3 dots signify that this is the 3rd element and the dots are placed near one side of the lens. This side faces forward so the dots were drawn closer to that side. Simple but very effective way of keeping track of things.

IMG_6457The front ring can be difficult to remove because it was secured with plenty of glue. Look at my picture to see what I mean. You can saturate this part with MEK and let it sit for a few hours. Repeat when every 30 or so minutes until you can unscrew this part with the help of a pair of rubber gloves. It took me a very long time to remove this so don’t rush it.

IMG_6453Once the front ring is gone, you can now separate the objective’s housing even further. It is important that you clean this part very well to remove any old grease or oil. The spring is sandwiched in between 2 brass rings. This spring pushes the aperture ring forward so it automatically clicks back into its own place.

IMG_6459Time to dismantle the iris. The rotation cup is being secured by this brass ring. Remove it by using a small precision screwdriver to pick it out.

IMG_6458The cup can now be safely removed. This cup rotates every time you turn the preset iris ring. I simple used my fingertips to remove this thing since my nails were long enough to reach down into it. You can also use a pair of tweezers and lift it by its walls.

IMG_6452This is our dirty iris. This can be frustrating to reassemble and if you are new to this then go read my article about working with preset iris type lenses. Note how the iris should be reassembled by studying this picture.

IMG_6465The iris can now be taken apart. I just dropped the iris leaves into a soft surface. You can remove it one-at-a-time but that’s time-consuming and may even be more dangerous. Use naphtha to clean the blades and wipe them carefully with a lint-free tissue. If you air-dry these then you’ll just leave some drying marks. I also noticed that these are thinner than average so handle these with care to prevent bending anything.

That’s it for the front barrel. The most difficult part for me was removing the front ring. I spent plenty of time on it just to remove it. I wasn’t even sure how it should come off and where I should start but I will spare you all the trouble so I’m showing it here on my blog to prevent you from doing costly mistakes. When reassembling this, never oil anything. It is the 2 ring that you turn that should be oiled and by that you only need a very thin-film of grease on the threads just to make it feel smooth. The slots on the inner surface of the aperture ring should also be lightly oiled so that it clicks without much resistance. If you lubricated these too much then the grease will just end up migrating into your iris and its leaves, this is just going to cause you trouble in the future and you’ll have to open it again sooner or later. Clean everything very well before you even begin to reassemble this.


I enjoyed working with this lens a lot. Its weirdness is a good break from the usual lenses in the Nikkor lineup. To be honest, I would like to overhaul another in the future. I hope I can get my hands on an S-mount version because I want to see how different that version is inside and out. Weird lenses like this keep me going because I learn new things and see new concepts just by working with them.

IMG_6461What an ugly lens but it’s now working smoothly and I have replaced all of the parts that needed to be replaced such as screws and other things. It’s really good seeing the fruits of your hard work! Good job, Richard!

Thank you very much for supporting the blog! I hope that we can have a broader base in 2018 so if you liked my work, please share it to your photography group! This is the only site on this planet that shares information on things that not many people talk about and this article is just one example. Nobody else makes a repair article for this lens and this is a welcome addition to our repair database! See you again next time, 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.

Buy me a roll of film or a burger?

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.


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