Repair: Nikkor 28mm f/3.5 Ai-S

Hello, everybody! It’s the middle of autumn and the trees here in Tokyo haven’t reached their peak autumn colours yet! This is starting to get frustrating for me because this is the only time of the year that I can justify shooting Velvia! Autumn is also about the time I use my wide lenses for landscape photography and I will show you one of my favourite lenses for general photography.


Today’s lens is the venerable Nikkor 28mm f/3.5 Ai-S lens! For a change, today’s lens is not mine and not a junk as well. It was sent in for repair together with another lens. I love this lens so much that I got one from the junk shops! I know, I am too cheap for this rich man’s hobby but there is always a way around things.

img_2137The 28mm focal length is one of my favourites and I own several 28mm lenses. Here is the Nikkor 28mm f/3.5 Ai-S lens together with the Micro-Nikkor 55mm f/2.8 Ai-S lens. Both are not mine and were sent to me for maintenance only. These 2 lenses make for a good setup for general photography since they compliment each other well in terms of focal length.

As you can see from the picture above, the poor Nikkor 28mm f/3.5 Ai-S lens can’t focus all the way to infinity and stop at around 5ft only. This was the reason why this lens was sent in for repairs. The lens is otherwise close to mint despite some caked grease underneath things like the focusing ring and the aperture ring. The grease has also started to go bad and I just cannot let it degrade further so I will do a complete overhaul of the lens barrel. The optics look spotless so far and I will leave that alone, it doesn’t make sense to open that thing up just for fun since it is not my lens anyway so I will keep the mutilation to a minimum.

The venerable 28mm family of lenses for the F-mount has a very long and rich history. The first lens to be made under this family is the Nikkor-H 2.8cm f/3.5 lens and it was one of the first Nikkors sold for the Nikon F – Nikon’s first SLR camera. The 28mm family is still being developed up to this day and most are considered to be really good lenses.

(Click to enlarge)

I’m going to send this lens back soon so I took it out for a quick test this afternoon at the park just to see how this thing performs. Sharpness seems pretty good even wide-open and if you stop the lens down to f/5.6 (1 stop), the image improves significantly. Flaring is also a problem for this lens as typical for this lens family since the beginning and it can be a pain since the image loses contrast here and there. I am not saying that this lens is bad, in fact it has improved significantly and the earlier versions flare like crazy.

The images were shot at around f/5.6-f/11 since it was reasonably bright this afternoon and it made no sense to shoot wide-open anyway. The image of the lady was shot at f/5.6 and if you can click on the image you will see that it is a sharp image. I can see the details of her eyeglasses’ frame and her wrinkles as well. The image has no artistic value but I added her picture into the mix since I was impressed by what I saw. It is also worth nothing that all of the images have been massaged a bit in Lightroom by adjusting exposure, contrast and white balance except for the lady’s picture which was cropped.

Having mentioned all of the above, I would still consider this to be a pretty good lens even on high resolution digital cameras. This lens is also pretty good when used in reverse for shooting extreme macro images.

2835aisThe optical formula for this has hardly changed since it’s debut in 1960 and the optics was only revised in the late ’70s. It is still the same 6 elements in 6 groups design but as see in the image above the curvature and design is totally different from one another and you can say that it is a totally new lens. It is a classic and a true testament to the optic’s design and not a lot of lenses can boast this. Owning a copy is like owning a piece of photographic history.

img_2434Here it is together with my Nikkor 85mm f/2 Ai-S lens. One lens for wide shots and another for tele. Both lenses are excellent and they were a joy to use ergonomically.

This lens is very versatile and you can use this as a walk-around lens and if I were given an option to only choose one lens to use when I travel to a dangerous foreign country then the Nikkor 28mm f/3.5 Ai-S or any of it’s kin will be on top of my list. You can use this for street photography, in fact Joel Meyerowitz is said to like the 28mm FOV since it gives him more space to tell a better story.

img_2431Here it is with the complimentary HN-2 lens hood. The older lenses flared badly and the contrast is not something that you should look for wide-open. As better coatings are used by Nikon, this problem started to go away. This version is OK even when shot against the sun but a hood will always be welcome just in case. The lens balances really well on a small but heavy camera like the Nikkormat EL. Focusing on older film cameras can be challenging because of the dark view that the slow f/3.5 maximum aperture gives you but it’s not really that bad and you will get the hang of it.

I am obviously showing my bias for this lens and I should stop the introduction now or else I will go on and on and we will never reach the next section. Let’s begin 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.

Disassembly (Lens Barrel):

This lens is pretty basic. It has a lot in common with the Nikkor 85mm f/2 Ai-S lens when it comes to the lens barrel/focusing unit. It can get really tricky because there are 2 helicoid keys and you should align them properly. If you got it the other way around then the lens will not focus properly and you will have to open it up again. Just take ample notes and do not forget to take pictures and notes and you will be fine.

img_2268Focus the the lens to it’s minimum focusing distance to reveal this set screw. Unscrew the thing carefully and store it somewhere so it won’t get lost or damaged.

img_2269With that set screw gone, you can now unscrew the front barrel off from the lens. It can’t be remove unless the screw is gone because it’s secures the ring by sticking into the thread thru a hole that was drilled in using a pin vice, a Dremel would have been too powerful.

img_2270Now, off to the rear. Unscrew these 3 screws from the bayonet plate. If they will not come off then place some alcohol or solvent on them and wait for it to work on it before you try to remove them again. Be sure to use the weight from your elbow to apply pressure so you will not accidentally slip and damage the screw or the lens.

img_2271The  bayonet should come off rather easily since there are no springs or any mechanisms that are connected to it underneath that you can accidentally damage so don’t worry.

img_2272The aperture ring comes off just like that and is not screwed to the aperture fork inside. It is good that I got to work on this before it got worse, just look at that caked grease on the chrome. It is a sign that the grease is starting to go bad. In fact, the helicoids felt a bit dry.

img_2273Carefully remove this ring. This is what couples the aperture ring to the iris mechanism in the objective’s casing. It restricts the movement of the lever that controls how much the iris should open up. Never lubricate this part, it works great just like that.

See that screw that I encircled? That screw should not even be there and it did not fall off from any of the parts inside the lens and there is not way this thing could have come from outside since it is too big to fit into any of the openings. It shouldn’t even be there!

img_2274This rogue screw is what’s keeping the lens from focusing to infinity. It is in the way of the objective’s housing’s path and therefor the lens will not collapse to it’s shortest length. The size of the screw is a hint that it belongs to a bigger lens, it’s possible that this got there by accident in a workshop somewhere. It has the usual red lacquer that Nikon uses so it is not from the factory because if it was then it should be clean because the lacquer is applied on the screws as a sort of an indicator if a lens has been tampered and as a sort of weak thread locking adhesive. The lacquer on the screw is dry and with signs that it used to be fixed.

img_2275The helicoids have 2 keys to keep it in sync, remove the screws to remove the keys but be sure to mark which one should go where because the keys are broken-in to their slots and it’s best that they should be fitted back again to their respective slots during reassembly to ensure it’s smooth operation or else you may end up with a rough-focusing lens.

img_2276By the way, before I removed the keys I focused the lens all the way to infinity and took the time to document it’s position when the lens is at this position as a reference later on so I will know how high this thing should be as an indication that I have the helicoids in their proper position. It is very easy to get confused and swap the position of the keys because there are two of them instead of the usual one.

img_2277To remove the focusing ring, simply unscrew these 3 screws. These screws hold that brass ring in place and that brass ring acts like a kind of pressure plate to hold the focusing ring down. I know that this sounds weak and inadequate but I will assure you that it’s enough and many Nikkors have the same setup, even higher-end ones.

img_2278The focusing ring came off easily. It wasn’t glued or anything so your shouldn’t have a any trouble. Notice that I have made a few faint scratches to indicate where things should line up with the infinity dot on the chrome ring. These faint marks are more than adequate to inform me about the alignment of these parts when the lens is set to infinity.

img_2279Now, it’s time to separate the helicoids! do not forget to mark where the helicoids separate so you will know where they should mate later when you reassemble it.

img_2280And now it’s time for the inner helicoid! As with the outer one, do not forget to mark the position of where they separated, for this I even added another one to indicate how high it should be when it’s seated properly and is focused all the way to infinity.

This is kind of annoying because the inner helicoid is milled into the objective’s casing. It also makes the objective prone to oil contamination. In fact, this one is close to having it’s optics contaminated with grease. It’s a very good thing that I got to it just in time!

Disassembly (Objective):

I have mentioned previously that the optics of the lens featured looks OK but I am going to show you another Nikkor 28mm f/3.5 Ai-S that wasn’t so lucky as it was dripping with oil! It was a pain so I decided to take the whole thing apart except for the front elements group. I had to do this just to make sure that everything is OK and since the front elements group’s condition is fine, I just let it be.

img_3072After cleaning the helicoid thread properly, I unscrewed the front elements assembly off. I then placed it somewhere safe and made sure that it doesn’t roll off the table and land on the floor accidentally. If you check the front element assembly’s casing carefully you will see that it has oil here and there. That has to go so I cleaned it properly with Q-tips and lens tissue that were moistened with Zippo fluid. I had to make sure that it is free from oil!

img_3074Now that the front elements assembly is stored safely, we can now work on removing all of the glass elements that are embedded in the objective’s casing. Unscrew this retention ring with your fingers and make sure that the rear element is facing up! This retention ring is what keeps it in place so without it, the rear element will free-fall to the ground. If you are really asking for it, the 4th and 5th elements will also go straight to the floor!

img_3075Use a lens sucker to remove the rear (6th) element safely and be sure to mark the leading edge with a dot using a Sharpie. The mark doesn’t have to big so long as you know which way faces the front of the lens. I do this for all of my lens elements unless it’s obvious to me which way the element should be facing. I also give it a code by drawing a number dots that correspond to the element’s number. For example, the 4th element will have 4 dots.

img_3076Once the rear element is gone, you can continue by removing this spacer that is placed in between the rear and the 5th element. Be very careful to also mark which side should be facing where because if you got this wrong during reassembly you will end up with a ruined element because the pressure from the incorrectly mounted spacer will crack the glass!

img_3077Use the lens sucker to remove the 5th and then the 4th element and as usual, do not forget to mark their element number and direction with a Sharpie pen.

img_3078Here is the 4th element. Notice that it is very ambiguous so you should definitely mark it’s direction to save you a lot of headache later. The 4th element was also drenched in oil and I had to wipe it clean with Zippo fluid and a lens tissue.

img_3079Here are the lens elements placed in their proper order. They will be cleaned properly and I also made sure that they are dust-free before I reassemble them back to their casing.

Disassembly (Iris Assembly):

This is bad. The iris is soaked in oil and this affects the exposure because the iris is sticking to itself. This problem is prevalent with this lens because as mentioned earlier, the thread of the helicoid is milled directly to the objective’s casing. I am going to use a thicker grease for this to prevent this from ever happening again and make sure that I apply it sparingly.

img_3080Take a look at that! Not a pretty sight. Before you disassemble the iris, make sure that you made enough notes or take a picture for reference. In this lens, there is a dot that’s left by the machinist and it corresponded to a hole on the casing – how convenient!

img_3081Now, go to the other side and remove these 2 screws. This will free the iris assembly from the objective’s casing so be careful not to drop the iris to the floor and damage it.

img_3083Carefully pick the iris assembly with a pair of tweezers while being careful not to touch any of the blades in the iris itself. These are delicately thin and they will warp easily.

img_3084It’s good that the iris assembly can be removed as a unit, that makes this a lot easier for us but before you go further you have to detach this end of the spring from a hook that can be found in the rotator plate. Use a pair of sharp tweezers for this and be careful not to ruin it or you will end up with a bent spring that looks funny and your iris won’t close properly.

img_3085Now that the spring is detached from the rotator plate, you can now remove it safely. Take note the iris blades are kept in place by the oil and without the oil, the blades will drop to the floor so open it like this to prevent that from happening.

img_3086The oily blades were dropped into a clean sheet of tissue to cushion it’s fall. They are going to be wiped clean with lens tissue and lighter fluid.


Wow, in order to make this a more complete teardown, I had to use 2 separate lenses just to get the job done. The 1st lens has pristine optics while the 2nd was dripping with oil. It all ended pretty well so I guess they’re both OK.

If you have been following my blog then you will notice the similarity between this thing’s construction and that of the Nikkor 85mm f/2 Ai-S lens. Both lenses were made around the same era so they share Nikon’s engineering standards for small Nikkor primes. Will this be a good project for a beginner? I think so, so long as you have the proper tools and observe properly how things were put together and mark how and where they separate.

img_3087After a thorough cleaning, the blades were put back into it’s casing. As you can see, the oil left permanent marks on some of the blades. This is just cosmetic and it will not affect the performance of the iris in any way so do not worry.

img_3088The rotator plate is put back into place and make sure that the peg on each blade is in their proper slot in the rotator plate. Make sure that it works before you proceed.

img_3089Now, here is the tricky part. In order to save you a lot of time and trouble putting the iris assembly back into the objective’s casing, simply rest the iris assembly on something that’s can fit into the interior of the casing. In this case, I used a small enamel paint bottle to do the job. Slowly lower the objective’s casing into position and carefully put the 2 screws back to secure the iris assembly before you flip it back. Check if the iris assembly is aligned with your mark and then tighten the screws until you are satisfied that it’s secure.

img_2281Before putting your lens back together, assemble it up to the point that I have here in this picture. Focus your lens on something far away like a building further than 4km away. See if the focus confirmation dot lit up in the viewfinder of your Nikon DSLR. Once it did then you have your lens properly focusing all the way to infinity. If you made a mark previously on where the infinity line should line-up if the lens is set to infinity then that mark should be lining up properly now like what I have in the picture.

Maintain your lens in this configuration and carefully reinstall the focusing ring and make sure that the infinity symbol on the focusing is centred with focus indicator line found on the scale of the lens barrel. Test it again to see if it’s still focusing properly to infinity and once you are satisfied then you can finish reassembling your lens. If you failed, just repeat the tedious steps until you get it to work properly.

img_2282Now it’s focusing back again to infinity! This is certainly one of the weirdest project that I have done. I have never seen anything like this and I doubt that I will see anything similar. I also used a stiffer grease for this and now this thing has the correct resistance when you turn the focusing ring. It feels so good that you want to turn this thing all-day!

This is going to be tale that I will tell my friends for a very long time and I am sure that this story will entertain everybody who is into photography. I hope that you liked this week’s blog post, we will talk about something interesting next week. Love, Ric.

PS: Thanks to reader Keith Barefoot for his input.

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.


7 Comments (+add yours?)

  1. Keith Barefoot
    Nov 20, 2016 @ 20:03:50

    Hi Richard,
    Thanks, as always, for your instructive service by posting these disassembly guides.
    One note: In this one, you state that ” The optical formula for this[the 28/3.5 AiS] has hardly changed since it’s debut in 1960 and was only tweaked minimally throughout it’s very long life.”
    In reality, the optical formula changed in a major way in early 1977. The old lens was the evolution of the Nikkor-H 28/3.5, which ran from the beginning to 1977. It originally had a pentagonal iris, and despite it’s mono-coating was unusually resistant to flare from strong point light sources like the sun. Multi-coating in the early 1970’s (the .C and K era) further improved the flare performance. The present lens was an all-new design in 1977. If you are a ’28mm nut’ as I am, it is probably worth owning both, as there are fascinating differences in the look of the images they produce.


    • richardhaw
      Nov 21, 2016 @ 00:23:33

      Hi, Keith!
      Thanks for pointing that out, I will edit it. What were the changes? it seems like the design was refined somewhat. I love the 28mm 3.5, in fact I actually own all of the Nikkor-H series. I don’t know I find that they flare more than I am comfortable with. Yes, the 5 sided iris takes a little bit of getting used to hahaha. Thanks again,Ric.


  2. Keith Barefoot
    Nov 21, 2016 @ 03:56:41

    The old design 28/3.5 has a strong “old time”, optically primitive style of correction. If you can get one cheap, check it out.


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  4. John
    Nov 26, 2016 @ 03:12:45

    Do you do repairs for other people? I’ve a 135 f2 DC that is badly fungus affected and a 50 f1.2 with some starting to show at the edges. The 135 is junk to me unless (or if) I can get fixed so I don’t mind taking a risk with it if you are willing to give it a go.


    • richardhaw
      Nov 28, 2016 @ 13:49:53

      Hello, John!

      Unfortunately I rarely do repairs for other people because of my long hours at work. How bad is the fungus on the 135 anyway and how bad? AF Nikkors are a pain to work with since they are engineered like puzzles. The 50mm f/1.2 is known to attract fungus under the front element. If the growth happened under the front element then you’re in for a hard time because it seems like it is in a sealed compartment together with the 2nd element. Ric.


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