Repair: Micro-Nikkor 5.5cm f/3.5 (2/2)

Hello, everybody! We are finally going to see the second part of the Micro-Nikkor 5.5cm f/3.5 teardown post! We were side-tracked a couple of weeks ago when I featured a teardown of the venerable Nikkor 35mm f/2.8 Ai but we are finally going to resume this series.


I can even make a third part but that will be too long and I am sure people will get bored with this so I am going to stay with the original plan of having just 3 parts.

Disassembly (Iris):

I am going to show you how to dismantle the iris assembly properly in this section. Please read part 1 as a refresher before you proceed so you will not get confused as to which part I am working on and how it got that way.

This part is pretty straight forward except for the iris assembly so please pay attention as this is going to show you something that I have never featured on this blog as of this post.

IMG_1900The rear element can simply be removed by your bare hands as it is just screwed to the end  the objective’s case. Ignore the fact that lens barrel is shown in the picture. I took this pic as I was disassembling the lens barrel earlier.

IMG_0147.JPGThis part will look different if you have the 2nd version of this lens but it should be similar enough. The pic shows the 1st version with the recessed filter ring while the lens that was disassembled in part 1 is the 2nd version with the raised filter ring.

IMG_0148The front element is simply screwed to the front cup and removing it is pretty effortless.

FullSizeRender 12As you can see from the picture above, the objective itself is tiny compared to the lens. Be careful not to damage any of the glass element when you handle it. You will also get your hand dirty with grease so be very careful not to touch any of the glass elements or else you will contaminate it with dirty decades-old grease which will take some time to remove and the alloy filings in it is course enough to abrade the coatings when you wipe the mess off!

FullSizeRender 6Remove the rotator cup from the objective and you can now access the iris assembly. Look at the picture carefully and you will see that my iris is contaminated with oil! This is not a good thing as you shall see later.

FullSizeRender 14Carefully remove the retention ring to remove the rotation plate from the iris assembly. It is the finely milled part with all the slots in it to guide the pins of each iris blade.

FullSizeRender 10Once the rotation plate is gone, the iris blades are free so be careful not to drop any or you risk damaging it and that is going to be a bigger problem for you and you may end up with a useless macro lens that will not stop-down properly.

The iris blades were so oily that it came off nicely in one piece. This looks interesting and it reminds me of a car transmission’s clutch part.

FullSizeRender 2Yuck!

FullSizeRender 11Not only were they oily but they were also rusty as well! Notice that the iris blade’s shape is not typical for SLR lenses. These L-shaped iris blades were pretty common in the preset aperture lenses used for rangefinder cameras,etc. Some of Leica’s lenses use this kind of iris blade shape like the Summicron if I am not mistaken. This lens was made during a time in Nikon’s history where they were transitioning from rangefinder cameras to the mighty SLR system that they will be known for eventually so it is an interesting link to Nikon’s rangefinder heritage. I do not know the merits of using this kind of iris type so please tell me anything you know about this and I will happily add that tidbit in this blog.

FullSizeRender 9The iris blades are now clean! As usual with iris assemblies, the last blade that you need to attach is the most problematic one as you need to slip it under the others. This problem is made more complicated with this type of iris blade shape. This is very frustrating and I had to spend plenty of time just to get this thing right.

It does seem that Nikon prefers to use this kind of iris blade shape for the preset lenses on the F-mount line. I am not sure about this so please do not quote me. I just came into this conclusion as another Nikon preset lens that I have opened has iris blades of this type,too.

FullSizeRender 3Oh, thank goodness it’s all done. Carefully reinstall the rotation plate and be careful about it’s orientation. Check your notes as to how it should be oriented before putting it back as removing the rotation plate may disturb the iris blades and you will have to put the pesky blades back together again. If you are a masochist then you would probably have a grand time with this. I am not, so I am warning you.

FullSizeRender 8When putting it back together, be careful of your tolerances. Always check your pictures or notes and you should be fine. You can record measurements as well if you are into that sort of thing.

Achieving Infinity Focus (Bayonet):

This lens was made in an era where Nikon had just made their first camera with the now legendary F-mount. Similar lenses of this era (late 50’s-early 60’s) will have the same issue as this lens because the engineers just cannot foresee what the future holds as well as the engineering challenges it brings as new cameras are designed and new concepts are presented. I will only discuss one issue on this post as it is the only thing that affects the use of this lens on modern autofocus Nikon cameras.

One such issue is the collar of the aperture rings from Nikkors of the same era. People had to grind away the obstructing part in order to make the lenses fit the Nikkormat family of budget cameras because the Nikkormat’s bayonet mount had a wider outer diameter than the one in the Nikon F (Nikon’s 1st SLR). Doing this ruins the aesthetics of the camera as  many were improperly modified or done using crude methods and tools.

55f35presetMount.jpgThe illustration above will give you an idea of what I am talking about.

On the above illustration (A), our lens is mounted on a modern Nikon camera. These Nikons have wider outer diameters on their lens mounts and thus, will prevent our 5.5cm Nikkor lens from mounting properly when the lens is focused to infinity. The inner diameter of the focus ring of our lens is just too narrow to accommodate the mount of the camera. You may successfully mount the lens to your modern Nikon camera but you cannot focus past the 1m/3ft mark because it is just impossible. Notice the green gap in the illustration, the 2mm gap is there and we need to bridge the gap if we want this lens to focus all the way to infinity when mounted to a modern Nikon camera.

The illustration to the right (B) shows this lens mounted on older manual Nikon cameras such as the F3/FM3A and earlier cameras (except the Nikkormat). Notice that there are no gaps in between the male and female parts of the bayonet and the lens fits properly. This is how it was designed to be anyway.

IMG_0789This picture clearly shows the problem when you mount this lens on a modern Nikon body without modifications made. Notice that you cannot focus all the way to infinity.

IMG_1886To bridge the 2mm gap, you need to mill a spacer for it. I milled one from acrylic as a test and prototype. This was sufficient and the acrylic spacer is still OK as of this date so I will just leave it there as milling one out of aluminium will take considerable effort.

IMG_1876When milling the spacer, take into account the raised ridge in the bayonet. Check the pic above to see what I am talking about. The stainless bayonet mount has a 0.5mm ridge in the inner diameter. This is probably used to catch stray light from entering the setup.

I drilled the 3 holes using a bigger bit than the original 2mm. This is to give me some room to position spacer. This was only intended to be a prototype/template so I needed freedom to adjust the position of the spacer and tolerances are a bit sloppy for now.

We also need to replace the 3 bayonet screws with longer ones since the whole thing was extended by around 2mm-2.5mm. This was easy for me as I have a box full of spare screws.

IMG_0790.JPGAnd here is the spacer in action. I currently do not have any intent to mill a new one out of aluminium but in the future, I may ask a friend to mill one for me since he has the proper machinery to do this. I would like to add some knurling into the new permanent spacer for a better grip. The guy has a machine shop so this should be an easy task for him.

Achieving Infinity Focus (Objective):

We managed to add a spacer in the previous step, now our focusing ring can now be turned all the way to infinity but the optics does not behave the way that it should because all we did was add a 2mm extension ring. To remedy this, we need to offset the rear elements by moving it around 2mm forward (towards the film plane). It would be ideal if we could just move the whole objective as a unit but this will require a lot of modification on the front cup and on the base where the objective is secured. I do not want to spend so much time and resources into this so I went with the easiest and most economic way that I know.

IMG_0150.JPGThis picture above shows that we can now rotate the focusing ring all the way to infinity. At this point, we still cannot achieve true infinity focusing since the optics are still off.

55f35preset2.jpgPlease take the time to study the illustration above.

The illustration to the left shows the original configuration of the rear element. We moved the whole lens forward by around 2mm so we need to get that 2mm back or else our lens will not focus to infinity properly because the optics were not designed to work like this.

The easiest way to do this is to simply loosen the rear element from it’s position and move it back by around 2mm give or take. Mount the bayonet back again and test it on a digital Nikon camera to see if the focus indicator dot would light up when you focus on a distant object like a building 2 or more kilometres away. Adjust the rear element’s position until you get it right (a solid dot on the focus indicator inside the viewfinder). This is a tedious step and it took me 2-3 tries before I got it right.

Once you got the position right, you can tighten and secure the rear element by using nail polish on the threads or a locking compound like Loctite. Never ever get careless and use super glue (cyanoacrylate) on this part or anything that has to do with optics as this will fog the glass up and your lens will be useless!

If you want to take it to the next level, you can use a brass, aluminium or a teflon washer to secure the rear element firmly in place. Just make sure that you get the correct height and diameter or it will be useless. Start by getting something that is just a hair taller than what you need and then sand or file it down to the correct height. For instances like this, having more material is better then having less. You can even use multiple washers to achieve the desired height. Combining multiple washers may be a better way to achieve this. It’s up to you on which route you wish to go.

IMG_1879It is also worth mentioning that the bayonet mount of this lens can be substituted for the one used in the M extension rings. Neat,huh? I got my first Micro-Nikkor 5.5cm f/3.5 with a screw mount instead of the proper F-mount. Somebody went bananas and made this mod. The previous owner probably wanted this lens so much that he adapted it to work with his system (probably Pentax). Nobody wanted the lens because of that and it was waiting there on the shelf for the right person, very much like the legend of King Arthur and the sword on the stone. I know it’s corny but a little ego-padding isn’t really that bad isn’t it?


I hope that you have enjoyed and learned from this post. I tried my best to condense all the information that I have so that I will not have the need to make a 3rd post but we still end up with a long article.

Some may argue that moving the rear element out of position will affect the image quality of this lens. That was also my initial thought so I did some tests on infinity and 1:1. What I got were sharp images and as far as I can see, no drastic change in the image at all. There is going to be some changes as the position was modified, that is for sure but whatever effect it has is negligible enough for me not to notice any degradation in my images. Again, your mileage may vary since I am not a pixel peeper and I am more for the overall usability of a lens. Modify your lens at your own risk, I will not be held responsible for anything.

IMG_1954.JPGThis post is important to the photography community as it discusses and dissects one of the rarest lenses made by Nikon and those who do own one do not usually go out and open their’s up for all to see or modify one to focus to infinity. The post has become a little bit technical so I hope that I did not confuse you. If there is something that is not clear, please feel free to ask me through the comments sections and if you have any useful input, you can share it there as well and I will update this post.

Until next time, please enjoy your Nikkors and we will be discussing another Nikkor in the next couple of weeks. Love, 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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2 Comments (+add yours?)

  1. the solitaire
    Jun 12, 2016 @ 14:28:47

    Very interesting write up and tear down. Excellent modification as well. Lenses are just far more fun when you can actually use them without getting out of your way to do so.

    The L shaped aperture blades allowed the diaphragm opening to remain rounded at all apertures. This certainly is true for the preset lenses Nikon released


    • richardhaw
      Jun 12, 2016 @ 14:58:05

      Thanks! the L-shaped aperture also gives me star-shaped bokeh-balls. Some Leica lenses have more than 10 blades if I am not mistaken. That must be frustrating to overhaul.


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