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Repair: Nikkor 28mm f/2.8 Ai-S

Hello, everybody! I am currently not feeling well today because of hay fever or the cold. I hate Winter but it’s something that I need to put-up with every year. Good thing that I am using a nice heater that I bought last week. It’s very good despite being inexpensive and small. I can now heat my room and work on repairing my junk gear. Nikon made plenty of great lenses that can be had for cheap lately and most of them are small but capable. I will show you one such lens today, it’s very popular and is considered to be a classic.

Introduction:

The Nikkor 28mm f/2.8 Ai-S has acquired a legendary status and many people claim it to be Nikon’s best 28/2.8 lens. I am not sure how good this lens fares against the modern one with the ultrasonic motor but I can say that this lens does live-up to the hype. It’s so good that it’s still being made and sold new at the present in 2018! That’s almost 4 decades and not many lenses can challenge this. Just imagine this, a lens that was introduced in 1981 is still being sold new at the present, that says a lot. Who are buying them? Scientists and collectors apart from photographers. This lens is excellent when mounted in reverse for extreme macrophotography and the aperture ring is essential for this kind of work. This lens can be considered as one of Nikon’s hall-of-famers due to its longevity and design. Its optical quality is excellent despite being an older design and is still relevant today.

IMG_0386The Nikkor 28mm f/2.8 Ai-S is a very compact lens. It looks deceptively simple but it’s one of Nikon’s most advanced lenses when it came out in 1981. This lens uses CRC so that it’ll focus really close and maintain its sharpness at this distance. This is one of the reasons it is being used by videographers because 28mm is a handy focal length and the ability to focus really close at 0.2m is even handier. You can shoot small bugs at this distance!

IMG_2993The lens came to me as part of a package. It has sever fungal infestation that’s so severe I cannot see through it clearly. I don’t mind because I am going to overhaul it anyway and I am not very picky with lenses so long as I get them cheap.

IMG_0387It was so filthy that even the rubber had fungi. I scrubbed it with a toothbrush and some dishwashing liquid. It’s now very clean and I hope that it remains this way. The CRC unit is what makes this lens amazing. CRC stands for “Close-Range Correction” and is Nikon’s trade name for “floating” elements. What this does is it changes the spacing of one of the lens’ optical block as you zoom in or out, making sure that it gives optimal performance in the whole focus range. The technology was first seen in the Nikkor-N 24mm f/2.8 Auto.

IMG_2520.JPGHere is the Nikkor 28mm f/2.8 Ai-S’ predecessor. The Nikkor 28mm f/2.8 Ai/K is excellent, I love mine and I still use it occasionally. This lens is excellent and it’s very hard to exceed it so Nikon really put everything into the Nikkor 28mm f/2.8 Ai-S to make sure that it will be much better than the old optic that it will replace. They also managed to make it just a bit smaller and lighter. This in itself is a huge achievement, congratulations!

Let’s see what this lens can do. I used to shoot with this lens a lot but I don’t remember if a photo I took was using this lens or not. You will have to trust me on this, this is a good lens for general photography. The ability to focus really close is also an asset.

(Click to enlarge)

The images above were shot from f/2.8 to f/11. Wide-open at f/2.8, the lens exhibits plenty of vignetting. It improves a lot by f/4 and is gone as you stop it down further. This is not a problem if you shoot landscapes because you will want to shoot from f/8 onwards. This is just to show you how vignetting looks like with this lens and I underexposed the shot just to show you that. You won’t normally see it this dark in normal conditions.

(Click to enlarge)

I’m not sure if shooting a heap of empty oyster shells is a good example to show this lens’ performance but here it is. These were shot from f/2.8, f/4 and f/5.6 (in that order).

If there is one thing that I hate about this lens it’s the poor flare resistance. You will have to keep in mind that this lens was a terrible fungus case so that may also contribute to it but it’s generally accepted that this lens is somewhat lacking in this department. I’m also shooting in abnormal conditions just to make these things appear so you shouldn’t take this too seriously. Landscape photographers on the other hand should find this useful as the Sun is usually in the frame for most landscape photos as part of the composition.

HAW_1872.jpgThis is what I am talking about. You will normally not see the flare when you’re shooting normal conditions. A hood will be useful in preventing that from happening. The lens is not really that bad as you can see from this picture so long as the light source is closer to the middle of the frame. Notice that it’s sharp at f/2.8 but some flare is taking the contrast away. Bokeh is also decent despite being a 28mm lens. You don’t shoot this lens for bokeh!

(Click to enlarge)

Now it’s time for some real-world examples! The 28mm focal length is wide but it’s not as wide as 24mm so it’s still great for shooting people at the street. You will have to get close because 28mm will force you to really close to your subjects. I love 28mm for this kind of thing because it enables me to have a little bit more of the background in the scene and I can make what’s closer to me bigger than what’s further away.

That’s all for the introduction. You can search the net for reviews of this lens, it is a very popular lens and it has been reviewed to death by almost everyone from casual shooters to people who shoot macro photography. It’s one of Nikon’s evergreen lenses and we will be still seeing people who will have use for this in the coming decades. If you don’t have it and you are in the market for a nice manual 28mm lens then this lens is for you!

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 lens barrel itself isn’t difficult to take-apart but it’s more complicated than the usual Nikkor small prime lens because it has CRC. The one thing that you need to pay attention to is taking measurements and notes. This lens has very tight tolerances due to it having CRC and you can’t adjust it to work properly if you got just one thing wrong. Always take plenty of notes and mark the important landmarks before you remove anything. Be sure that the lens is focused to infinity while you are working on it so you will have a point of reference. This lens is not for the beginner and experienced repairers will also find this lens challenging to say the least. Just leave this to the experts, if yours needs repair then send it to a reliable repairer. This lens is not easy to service so it will cost you a bit more.

IMG_0390Nikkors of this era (smaller primes) tend to have something in common, they are usually best opened from the rear. Begin by removing these 3 bayonet screws. If you’re new, see my article on how to work with bayonet screws. Many newcomers get stuck here and I’m going to show you how not to get into that situation.

IMG_0391The bayonet mount can be easily removed just like this, be careful not to damage the lens at the rear as it’s now exposed.

IMG_0392Take note of how things look like before you proceed. I make sure that the lens is always focused to infinity while I work on it. This gives me a point of reference later when I am going to reassemble the lens. This lens has CRC and this makes things more complicated, make sure to take notes and make marks where needed.

IMG_0393This ring regulates the size of the iris and it can easily be removed. Take note that the tab should fit into a slot in the aperture ring. The tab should never be removed as it was set at the factory. If you mess around with this then the opening will not be as accurate.

IMG_0394The aperture ring can now be safely removed. Look at how dirty everything is, this lens is definitely one of the dirtiest lenses that I have worked on.

IMG_0395Make sure that the lens is focused to infinity and mark the position of the 2 helicoid keys’ edge. After reassembling your lens, you should get the same result or else you will have to reassemble it again because this just means that you got everything all wrong!

IMG_0388Time to go to the front end of the lens. There are 2 screws here that you should remove. I am not sure if there’s only one screw for other lenses but I have 2 on this lens. Once the 2 screws are gone, you can now unscrew the front barrel off.

IMG_0396You can remove the rubber grip by running a small wooden toothpick under its length to lift it from the glue that was used to stick it. Make sure that you don’t tear the rubber or you will have a baby coming. Sorry for the crude joke, I just wanted you to laugh a bit.

IMG_0398This is the tab for the CRC unit. It goes up and down along its slot as you focus. While the lens is still focused to infinity, mark where the tab is supposed to be. You should check if it’s back at this position later during reassembly.

IMG_0399Now that we have taken note of all of the important landmarks, we can now proceed to separate the helicoids. Remove the 2 helicoid keys and mark which one should go where. It’s best to put them back to their original places, notice that I made a small mark for this.

IMG_0400I would normally remove the focusing ring before separating the helicoids but the lens is a special case. There is a sequence for you to achieve this but it’s too much work so I just settled with this. Always remember to mark where the helicoids separated because they should mesh in the same orientation. If you forgot to mark it then you will be wasting a lot of time guessing where they should mesh. If you haven’t read my article on working with helicoids then please head there to read it and watch the video.

IMG_0397Now that the lower half of the lens is out of the way, you now have more space to wiggle the focusing ring and remove it. The tab for the CRC unit is in the way so you will need to find a good angle to remove the focusing ring. The focusing ring is being secured by that brass ring. Remove the 3 screws to free it and you can begin the business of removing it. Take note that this is also where you should calibrate your infinity focusing.

IMG_0401After a bit of patience, the focusing ring is now free! If I recall it properly, the front lip of the focusing ring can be unscrewed but it’s being secured by contact cement so I just left it alone. This will only soften when you saturate it with alcohol or soak it alcohol bath for some time before you attempt to remove it. It can be delicate so I just left it alone.

Remember to mark where the inner helicoid separates with the central helicoid. Always make this a habit every time you work with helicoids.

IMG_0412Time to remove the front optical block. You can remove this as soon as you can access it, I just removed it now because I don’t want to disturb the CRC unit’s orientation.

That’s all for the lens barrel. It certainly felt like a mini-puzzle when I was working on it. It took me longer to disassemble this lens because there’s so many things to consider. Do not rush it and just take your time studying how it works and taking measurements of it and you should be fine later during reassembly.

Disassembly (Objective):

The lens elements can easily be removed but just be careful with some of the elements, it may have been sealed with lacquer. This lens also has adjustable lens elements where it’s possible for you to fine-tune your lens’ element position. Other Nikkors also have this but as far as I know, this is usually found on wider Nikkors with CRC implemented.

IMG_0413The rear element can be removed by unscrewing this collar. If yours is stuck, just apply a small drop of alcohol to it’s thread to soften up the lacquer used to seal this.

IMG_0414The rear element can be removed with the help of a lens sucker.

IMG_0415Next, remove this spacer and take note of which side should be facing where. If you put it back the wrong way then you can damage your lens!

IMG_0416Time to remove the next element with a lens sucker. Note that I have marked the leading edge with a Sharpie marker to remind me which side should be facing front. The number of marks also indicates the element number so this will help me later.

IMG_0417The last element on the rear optical block can now be safely removed with a lens sucker. Again, notice that I marked it to help me later.

IMG_0418The inner element can be removed by unscrewing its housing off with the help of a lens spanner. The 2 dimples should give you a glue on which tool to use. This lens has fungus damaged but we will take care of that later! Notice that it was sealed with lacquer so you will want to apply some alcohol on the threads to soften it first. This element was sealed by the factory because you can adjust this to give optimum results. If you’re really into it, you can measure how deep this thing goes before you remove it or mark its position with a small scratch on the walls of the housing and see how far it will go when you tighten it. I don’t recall making this but my lens worked fine, I’m just mentioning this to you so you know where you can adjust your lens to get it to be pin-sharp. Many other Nikkors have this kind of adjuster. Wow, just look at how dirty this thing was.

IMG_0419You can now extract this after you unscrew it off from the objective’s housing.

IMG_0433The front element can be accessed by removing this ring. Again, if it feels stuck then drop a small amount of alcohol to soften the lacquer.

IMG_0434Remove the front element with a lens sucker. Remember to always face this thing up all the time while you work on this or else you will drop its contents to the floor!

IMG_0435Next, remove this spacer. Always remember where this thing should be facing.

IMG_0436The 2nd element can now be safely extracted with a lens sucker.

IMG_0437The same goes for the 3rd element.

IMG_0421The last element of the front optical block can be removed with your barehands. It’s not advisable to remove it from its housing, just leave it there because it is sealed.

Make sure that you clean the elements properly before you reinstall them. A lens like this had to be cleaned very well to prevent the fungus from coming back. Sure, spores will be near-impossible to kill and all you need is one single spore. Spores are everywhere so it’s also important that we keep the lens clean and use it often to prevent it from fungi.

Disassembly (CRC unit and Iris Mechanism):

I decided to combine the CRC unit and iris mechanism into one section because they are situated in the same place and it’s easier to read this article with them combined. This is going to be a bit difficult because there are many things that can go wrong here so please take as many pictures and measurements as possible. If you put the CRC unit back in the wrong manner then everything will be off-sync and your lens will not work optimally. It is absolutely important that you get this right.

The inner helicoid also houses the objective and it’s kind of common for lenses in the Ai-S era to be made this way to save cost and to make things lighter. This has a big drawback because the objective and the iris mechanism is sitting really close to the helicoid so any oil that migrates from the helicoids has a big chance to settle in the iris mechanism. This is the reason why this lens is prone to the oily iris problem. The CRC unit is also close to it and sits right above it so that’s also another source of contaminant oil.

IMG_0420Time to dismantle the CRC unit! Take plenty of notes on its orientation and positioning. It is also important to make measurements whenever prudent. Before removing the tab, be sure to mark its position very well. I mark the ends of the tab on the metal surface that it is on so I will know how to put it back. Notice that Nikon sealed it with lacquer, this is not only to make sure that it doesn’t move but it’s also Nikon’s way to see whether somebody worked on it before. It it’s gone then it’s most likely tampered.

IMG_0423Here’s where I made my marks. I only needed one, but I just wanted to be sure.

IMG_0424Mark the height of the tab for reference, this is very important so you will know how to put it back the right way later.

IMG_0425Take as many pictures of it before you remove it, this is your last chance.

IMG_0426The point of no return! Don’t worry, I made a mark to help me later on.

IMG_0427Time to to remove the CRC unit’s helicoid. Again, mark where this thing separated. If you failed to do this then you deserve the agony of finding out how to put it back properly.

IMG_0422The iris mechanism is secured by these 2 screws. These are also adjustable if I’m correct, mark them properly so you will know how to position it back again later.

IMG_0428The iris mechanism will is also sealed by this collar. Use a lens spanner to unscrew it. See the lacquer? Do that alcohol routine again here. Again, mark how deep this thing goes as I suspect that this is another adjustable part.

IMG_0429Remove it when you’re confident that you can put it back together properly again.

IMG_0430The iris mechanism can now be accessed. All that effort just to get to this!

IMG_0431It can be easily removed by pushing on it’s post from behind and lifting it off. It’s spring-loaded so be careful or your iris blades will fly to the floor, damaging them forever. The spring can now be disengaged by using a pair of tweezers.

IMG_0432Now it’s ready to be cleaned!

The helicoid for the CRC unit should only be lubricated with a very think film of grease. I will caution you against putting too much grease here because there is a very big chance that the grease will migrate to the iris mechanism. Use a light grease here, a thick grease will only make your lens difficult to turn. Remember that you will be turning 4 helicoids in all so the resistance from each helicoid will add-up. If your helicoid has dried grease, I would even use a very fine steel wool to scrub away any dirt. It’s not unusual to pick-off any dried-up grease with a sharp toothpick and you will have to do this sometimes when you find any caked gunk in your helicoids. Leaving it there will only make your lens feel gritty as you focus. The helicoids should feel smooth even when dry-turning them. If it’s rough then you will have to scrub it more using a kitchen sponge.

Conclusion:

This lens took me longer to put back because of the numerous parts involved. I also took extra time to make sure that things aligned properly before I reassembled the lens. These lenses with CRC always take extra time because you will need to test it after reassembly. I just focus the lens at infinity and check its sharpness and do the same thing on the other end. The mid-ranges will also have to be checked just in case.

There are a couple of issues to look out for such as:

  1. Sharpness should be even, if one side is sharper or in-focus then you’ll have to see if you got the elements set properly.
  2. Ugly or weird artifacts on the edges when focused on its closest focusing distance. If it looked weird, you will have to adjust the central element’s height with its adjuster ring. This can be tedious and you won’t have to do this if you took measurements of its depth early on before removing it, that is if the lens hasn’t been tampered.
  3. The lens should focus properly to infinity and be able to focus as close as 0.2m. You will have to calibrate your focus properly. If not then you have put the lens back the wrong way and you will have to reassemble it again until it this works.

Make sure that you don’t lubricate the lens too much, any excess oil will migrate to its iris or other sensitive mechanisms. As a general rule, CRC lenses should never be lubricated too much and you should use grease that’s not so thin as to make it run or a thick grease that will seize-up the helicoids. Only use good grease for this like silicone grease that has been formulated for lenses to prevent it from caking and evaporating. Evaporated oil is going to settle on the lens elements and is one of the most common causes of haze.

IMG_0442Here are all of the elements, clean and dry. I cleaned the fungus using the method shown in my very popular fungus removal article. The iris blades were individually cleaned, it’s important that you clean them very well with naphtha and carefully wipe them dry with a lens tissue. Air-drying them will leave some drying marks depending on which solvent you use. Be careful not to warp them or else your iris will never operate properly again.

IMG_0443Carefully reset the iris blades back to their position. This is easy because it only has a few blades. Just wait until you see how many blades a preset-type iris has!

IMG_0444Just look at how clean it is now! Just a couple of minutes ago this was filled with fungi!

IMG_0446The easy way to put this back is by using something to prop up the iris assembly. I use my wife’s nail polish remover (acetone) bottle because the cap is of the correct diameter.

IMG_0447Next, carefully lower the objective’s housing over the iris mechanism, very easy.

IMG_0448Once you are happy with it, screw it back together and you can now reinstall the spring.

IMG_0450Time to put the CRC unit’s helicoid back into place. See how handy the marks that I made were? This is my lens so I don’t care as much. For other people’s lenses, the marks are a lot smaller and they are made on more discreet places.

IMG_0451See how clean it is now? The brass ring secures the focusing ring. Reassemble your lens back but don’t put the front barrel back so you can access the screws of the brass ring. It is important for this lens to focus perfectly and this is where you can adjust it. Please see my article on how to calibrate your lens for infinity focusing. It may take some time but it is going to be worth it in the end. No excuses here.

IMG_0452Look at how clean it is! Even the black ink on the walls of the lens is all gone! I stripped it by soaking it in alcohol and removing the old black ink. This was necessary because the fungal infestation was severe so even the black lining had to be replaced. I use the best India ink (China ink) I can get and I repainted the walls of the lens again with fresh ink. I can now be sure that the chance for the fungus coming back again is now much lower.

IMG_2035What a lovely lens. See how clean it is now? Even the numbers look clean and whiter. It’s a very satisfying experience for me every time I restore a lens back to working condition.

That’s all for the Nikkor 28mm f/2.8 Ai-S lens! I have been getting requests to do this for a long time but I only got into the mood to write this just now. I am busy juggling my time between doing this, work, family and my hobbies. I really do not have much free time to be honest so I hope that you enjoyed this article. There aren’t a lot of things online for it, I hope that this will be helpful for people who wish to repair this lens. Again, this lens isn’t something a beginner should be working on and experienced repairers should be careful with this lens. If somebody quoted you a higher price to work on this lens then you know now that this lens isn’t of conventional design. I would say that I will ask 150% for this if somebody asked me to work on this just to cover for the time and effort needed to make sure that everything works properly. This lens is very time-consuming to say the least.

Thanks for the support! I hope that you love this article and if you did, please share this with your friends at social media and your photography club! This will help us grow, we are currently hitting around 30,000 views a month and I aim to hit 50,000 this year. This is not shabby at all considering that this blog is written and maintained by one person, it also targets a very specific audience so I need your help to turn this blog into the biggest Nikon-related blog online. Can we do it? I am sure we can! Let’s show them the power of teamwork! See you guys 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 paypal.com account (richardHaw888@gmail.com). 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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Thank you very much for your continued support!

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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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4 Comments (+add yours?)

  1. Bill Balinor
    May 14, 2018 @ 02:11:29

    You’re doing God’s work, Richard. I hope you never stop while you have your health.

    Reply

  2. whycomeimsocool
    Jul 04, 2018 @ 10:13:26

    Hey Richard ! Thanks so much for this guide 🙂 it obviously took a lot of diligent effort, and time – much appreciated. I wanted to ask if I’ve completely bricked my lens by removing all the screws and tabs you say not to remove (set by factory, etc), or if there’s a way I can meticulously & patiently get it back together again, properly calibrated. What are your thoughts? Local repair shop wants $120 to do it (just a bit less than what I paid for the lens in the first place), so wanted to give it a shot on my own first.

    Thanks again!
    -Ray

    Reply

    • richardhaw
      Jul 07, 2018 @ 17:38:36

      Hello. For that price it has to be a COMPLETE overhaul. I would charge about the same for that lens. I am not sure which screws you’re talking about or what’s going on with your lens. All I can say is that this lens is not for beginners. Ric.

      Reply

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