Repair: Nikkor 50mm f/1.8 Ai-S

Hello, everybody! It has been a busy week at work so I haven’t got the time to update this blog for 8 days. It is pretty difficult striking a perfect work/life while working here in Japan as the working hours tend to be long and can sometimes encroach on weekends and by the time you got home, you are left with just enough time to clean yourself up and read your email. All that plus the expenses of rearing a child makes things difficult for the average person working here in Japan – No wonder people here prefer to be single all their adult life!

Having mentioned all that, I am still grateful that I have a wonderful family who supports me in the profession that I chose and for encouraging me to write this blog. With what was left of my time this week, I am going to post a short but interesting tear down of a popular Nikkor lens that has become a favorite due to it’s small dimensions and the amazing cost to performance of this little gem – the Nikkor 50mm f/1.8 Ai-S.



I had a Series E version several years back and sold it a long time ago and since then I have always wanted a small pancake-like manual focus prime for my Nikons. I could buy myself another Series E lens but decided to get the Nikkor version instead since they usually cost the same in the used market so there is no sense in buying the Series E for me if you can get something better for the same price.


As you can see from the picture, the lens has a very low profile and the only thing shorter in Nikon’s lineup would be the two 45mm’s. It is also surprising that Nikon has packed so much in such a compact lens that the performance of the Nikkor 50mm f/1.8 Ai-S rivals the output of much bigger and more complex lenses like the Nikkor 50mm f/1.4 Ai-S. This unique feature has earned this lens a spot in many Nikon photographer’s heart.


This is the perfect travel and street lens if you want to be discreet. I actually find that the subjects that I shoot did not even notice me shooting at them even if I was just a meter or so away from their faces. If i were to do this with the Nikkor-S 50mm f/1.4 (which is twice as big) then my subject would easily notice my camera and drop their heads as quick as they can and I would miss a potential shot. The fast f/1.8 maximum aperture is also helpful for creating an artistic rendering or for shooting in low light situations.


I got this lens in a pretty decent state, the glass was clean with the usual amount of dust present inside as expected from a lens of this vintage, the focusing was smooth but stiff. I can live with the dust inside the lens but I have to do something about the focusing. I take pictures everyday and manual focusing with a stiff focusing lens will tire you eventually because you need to apply more torque when you twist the focusing ring as well as run the risk of damaging the rubber on the focusing ring while doing so.

Having fixed similar lenses before and knowing what to expect, I decided that I should give this lens an overhaul it deserves.

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 (Main Barrel):

The main barrel of the lens is simple enough but the cramped internals may be a bit intimidating for people who are new to this. Being and Ai-S lens, Nikon has employed lots of clever short-cuts in this lens to cut cost and make this lens compact. It should be common sense to take as many notes as possible since this is more complicated as compared to your usual prime lens from decades past. Read on!

IMG_1324First, remove the 3 screws that secure the bayonet mount to the rest of the lens…

IMG_1325and bayonet mount and the aperture ring should come off easily. Be careful not to bend the aperture claw that comes in contact with the aperture assembly on the objective.

IMG_1326Next, turn the focusing ring until you see this tiny set screw. Loosen it just enough so that it does not come in contact with the screw thread underneath it. You really do not want to remove this from it’s screw hole if you can help it.

IMG_1328Get a rubber stopper and turn the front barrel counter clockwise to loosen it and make sure that the tiny set screw mentioned in the previous step is loose enough to allow you to twist the front barrel off.

IMG_1329The front lens element is exposed once you got rid of the front barrel so be sure not to damage it.

IMG_1330Now, back to the other end of the lens. Remove the screws securing the chrome grip and it should come off just like this. Sometimes, Nikon would apply an adhesive to this part and you would have to apply acetone to this area to loosen it up before you can remove this.

And as you can see from the picture and if you have been following my blog you will see that the chrome grip also acts as a helicoid stop just like the one on the 85mm f/2 Ai-S that we had on our previous lens tear down.

IMG_1331This step is very important so please mark where the infinity mark is in relation to the rest of the lens. Be sure that the lens is focused all the way to infinity when you do this.

IMG_1332In order to remove the outer helicoid from the rest of the lens, you will have to remove these 2 helicoid keys. Be sure to mark one of them so that you know which one should go where when it’s time to reassemble your lens. If you accidentally jumbled them up then you might end up with a rough focusing lens since helicoid keys are broken in to their own respective slot.

IMG_1333Carefully remove the rubber grip and make sure not to tear this part since it is made of soft rubber and this one is thinner than most rubber rings from Nikon. Once the rubber grip is gone, you can now loosen the set screws holding the focusing ring to the outer helicoid.

IMG_1334This is the reason why I told you mark where the infinity mark is on the lens, this whole thing is just being secured by 3 small set screws! If ever you fouled up your infinity focus, this is where you can adjust it so that your lens can focus all the way to infinity.

IMG_1336You can now safely separate the helicoids from each other but just be sure that you mark where they separate or you will have a hard time figuring out where they should mate.

IMG_1337The innermost helicoid also serves as the objective for this lens. Nikon has to do this in order to save production cost and space. This also means that this lens is prone to grease migration if you are not careful.

Be careful when cleaning this part because you do not want to accidentally contaminate the insides of this assembly with dirty solvent or lighter fluid. The other parts of the iris assembly are also exposed (like the pins of the aperture blades) and you want to stay clear of these as well when cleaning this part. Just clean it enough to get the old and dirty grease from the grooves. If you really need to clean it thoroughly in the case of a really bad fungal growth then you should tear this thing apart.

Disassembly (Lens Elements):

Taking apart this lens to access the lens elements is pretty straight-on but you should be careful at handling the lens elements or you risk damaging any of them. You will not have to use any special tools to access anything here apart from a rubber cup or a lens sucker. A lens sucker can be made from a toy pistol’s bolts.

IMG_4851The front elements group can be separated from the casing by unscrewing it. To get to the front element, you should use a rubber cup to unscrew the retainer ring. Just be careful not to drop the front element to the floor and do this while everything is facing up! Nothing is securing the lens element at this point!

IMG_4852A lens sucker is the safest way to extract the front element…

IMG_4853The 3rd element is glued to a housing and it can be unscrewed. The casing of the 3rd element also secures the 2nd element so be careful not to drop the 2nd element! Just have everything facing down just like in the picture  and you should be OK.

IMG_4854The bulbous 2nd element can now be safely removed with a lens sucker.

My apologies! I forgot to take pictures on how to remove the rear elements! I was too occupied with working on the lens. I will just elaborate on it here without using any pictures so I hope that you have a good imagination! Be careful and have everything facing down while doing this or your lens elements will drop to the floor!

  1. Remove the retaining collar by unscrewing it. It may be glued in place so put a drop of alcohol or 2 to soften the glue or lacquer.
  2. Use a lens sucker to remove the rear element and to be safe, use a sharpie and make a small mark to remind you which side should be facing forward.
  3. There is a metal spacer in between the rear element and the one in front of it, I would suggest using a a pair of tweezers to pick that out from the casing. This is not symmetrical so please mark which way should be facing forward.
  4. The inner elements can now be accessed. Use a small lens sucker that would fit inside the diameter of the housing. Again, be careful not to drop anything!

That’s all there is for now. This is still pretty basic compared to the more complicated designs. I would not worry too much about this.


This lens was easy enough to service that you can overhaul this little gem in under 2 hours. While putting the lens back together, you have to be careful about the focusing ring and where it should be positioned so that you can get precise focusing to infinity.

IMG_1338This lens also has a reputation for stiff focusing and the reason for this is partly due to how small this lens actually is since the helicoids are made thinner but the actual reason for this is people tend to forget to lubricate the aperture column as well as the helicoid keys. This lens is so small that small things like these will all add up, resulting in a stiff focusing lens that squeaks. Just make sure that you do not put too much grease on these parts or else you will end up with oily aperture blades!

And finally, do not forget to add a thin strip of double-sided tape on the focusing ring just before you put the rubber grip back or else your rubber grip will slide when you turn it.

When serviced properly, this little lens should provide you with many more years of fun. The lens itself is fragile compared to other Nikkors of the same vintage with the focusing ring as weakest part. You should not use too much force on the focusing ring anyway since you can focus this lens with only one finger and this should not be a problem unless you abused this lens.

On my sample, I did not have the need to clean the optics since it is still clean but if you need to clean yours then this lens will not be too much of a trouble because the elements and the assembly do come apart easily. The only thing that you have to be careful of is accidentally dropping any of the glass elements since some of the lens elements were not secured with a ring any adhesives. To prevent this, always open this lens facing up so that gravity will keep these in place.

I hope that you have enjoyed this article and if you did, please do not forget to share this. Clicking on the ads that appear on my blog will help a lot so that I can get the initial cost of paying for a domain name back.

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.


21 Comments (+add yours?)

  1. doc a
    Feb 19, 2016 @ 07:15:44

    Ang galing naman..salamat sa pag share uli..


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  3. Fadion
    Aug 06, 2016 @ 19:54:53

    I have a 50mm 1.8 AIS that had some fungus and a loose focus ring. It looked like an easy job, so I opened and cleaned the optics. Didn’t like the loose focus ring, so I disassembled the helicoids too. Unfortunately, I saw this article after I messed up. Didn’t mark the focus position and I have no idea how to realign. Any suggestion will be immensely useful.


    • richardhaw
      Aug 07, 2016 @ 03:55:56

      Hello, Fadioni! Unfortunately, you will have to find that out for yourself. You can check the other guides online and see where their helicoids lineup and try to guess it yourself. Ric.


  4. fadioni
    Aug 06, 2016 @ 19:55:33

    I have a 50mm 1.8 AIS that had some fungus and a loose focus ring. It looked like an easy job, so I opened and cleaned the optics. Didn’t like the loose focus ring, so I disassembled the helicoids too. Unfortunately, I saw this article after I messed up. Didn’t mark the focus position and I have no idea how to realign. Any suggestion will be immensely useful.


    • scott
      Oct 09, 2016 @ 11:12:32

      Ive made the same mistake not marking before separating helicoids. Driving me crazy, trying to find some footage of re assembly. There must be a method approach?


      • richardhaw
        Oct 10, 2016 @ 10:26:47

        Hi, Scott!

        Unfortunately, there isn’t. You rally have to mark where they separate. You could guess where they mate by rotating one of the helicoids the other way and hear a slight audible click. That click where the helicoid would mate. Looking at the thread also helps. If something like that happens to me, I would look at other people’s assembly notes to find some clues. Check my post on helicoids, it may have something. Ric.

  5. Trackback: Lens Repair (2): Major Parts of a Lens (Manual Focus) – My Take on Photography and Diving (Underwater Photography Mostly)
  6. Trackback: Internet Nikon Repair Resources – My Take on Photography and Diving (Underwater Photography Mostly)
  7. Carlos Fernandes
    Feb 19, 2017 @ 18:54:54


    Need some help, at least just to know if the following has even happened to you.
    I have followed your post and have disassembled a nikkor 50mm 1.8 e-series ( silver version) . It is a bit different from this post but allowed me to have a direction and the necessary advice.

    Anyway, I had a problem while putting the lens back together.
    I have stiff, very stiff focus. It is almost has the helicoidal don’t fit any more.
    It is if the plastique male helicoidal and the female aluminium do not fit any more.

    Has this even happened to you ?
    If so it there a solution ?

    Thanks for your help.
    Carlos – Portugal


    • richardhaw
      Feb 20, 2017 @ 05:37:19

      Hello, Carlos!

      I think I may have made a mistake there, I checked and the helicoids are indeed both made of metal, they only look like plastic so that tricked me.

      As for stiff focusing, be sure to check the helicoid keys and see if they are seated properly. Sometimes, they may not have been seated properly. What I do is before I tighten the screws of the helicoid keys, I focus the lens in and out to see if it’s OK and then I tighten the screws. Good luck, please message me when you have problems. Ric.


  8. Carlos Fernandes
    May 01, 2017 @ 16:17:14

    Hello Ric

    Thanks, You were right, I have taken the lens apart again, and very carefully followed your “instruction”. Its working very very well.

    I have a slight problem but I will ask on another thread.

    Thanks one again.



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  10. Chul
    Sep 20, 2017 @ 15:24:11

    Hello Richard,

    I’ve just acquired one of these lenses. It has two main faults: the corners are very soft up to f/2.8, and when you turn the focus ring back and forth, the image shifts slightly, I’m guessing due to a loose helicoid. Can you please advise, is there anything I can do to remove the slop in the helicoid? (I have not yet taken the lens apart.) And is there anything I can do about the corner softness?



    • richardhaw
      Sep 22, 2017 @ 01:22:36

      As you focus in and out, sometimes the framing would change. This is called focus breathing and is normal with many lenses.
      I am not sure about the corner sharpness. Very hard to tell unless I have the lens with me. Best thing to do is look for a similar lens and then try that. If that lens is OK then yours is probably not. Ric.


  11. chulerino
    Sep 20, 2017 @ 15:24:37

    Hello Richard,

    I’ve just acquired one of these lenses. It has two main faults: the corners are very soft up to f/2.8, and when you turn the focus ring back and forth, the image shifts slightly, I’m guessing due to a loose helicoid. Can you please advise, is there anything I can do to remove the slop in the helicoid? (I have not yet taken the lens apart.) And is there anything I can do about the corner softness?



  12. S. Staten
    Nov 18, 2017 @ 22:59:18

    Hi Richard, I just got this lens from Japan and it had a sticky focus ring. I disassembled and re greased the outer helicoid which fixed the problem, you tutorial was invaluable. Thank you so much. One thing you might want to add is that the outer helicoid separates without warning. I was ready to mark it for re-assembly but by the time I realized what had happened I was too late. I ended up trying each starting position methodically until I reached the right one… a long afternoon and evening. but the lens is so much smoother now. Thank you so much for these tutorials. I did the Micro Nikkor Auto 55 3.5 from your tutorial too. I looked for the Nikkor 85 1.8 H Auto from you but alas you don’t have this one. However I did find something in the end…. All the best. and many many thanks again for this valuable resource. Steve.


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