Repair: Nikkor 50mm f/1.2 Ai-S (Dust Removal)

Hello, everybody! I am currently busy studying Unreal Engine this holiday and weekend so I do not have a lot of time to write a lengthy post. My baby is also getting bigger and bigger and she now requires more attention as she is now capable of walking fast!

Anyway, a couple of people have talked to me regarding today’s problem and this is how I solved mine.


The Nikkor 50mm f/1.2 Ai-S is a fine lens and needs no introduction. I love mine a lot but it has a tendency to accumulate dirt in the middle elements and for some reasons the inner surface of the front element tends to be prone to fungus.


Fortunately, my lens is pretty new and no fungus been seen growing in it yet. The specks of dust and debris are pretty big and can be seen with the naked eye. I suppose that these will not affect image quality but will be visible in bokeh balls when underexposed. This is unacceptable to me so I am going to open up mine to blow these nasty things away. If you have a dusty Nikkor 50mm f/1.2 Ai-S then this is how you can clean the middle elements painlessly. Fortunately, dust seems to accumulate here more then anywhere else.

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.

Essential Tools:

Fortunately for us, we do not need any special tools to open this and blow away the junk in the middle elements where it tends to accumulate. I’ll show you why this is the case later.


All we need are:

  1. small precision screwdriver (-)
  2. JIS screwdriver (+)
  3. bulb blower
  4. flashlight
  5. acetone/solvent

Always work on a clean surface whenever you can. For the people who follow my blog, I am sure that you have noticed that I am not working on the floor this time around. For safety, I placed a kitchen towel on top of my table in case a screw fell so that it would not bounce on the wooden table and break something or gets lost. I am very careful with my lenses but you cannot be too careful and the kitchen towel will prevent any scratches to the elements or worse. A rubber mat would be better but I do not have one at the moment.

As you can guess from the lighting, it is pretty early in the day and I do not want my wife to see me working on a lens on the kitchen table. That is her territory


This is a pretty simple routine because we do not need to work on the focusing unit. All we need to do is access the objective (optical assembly) , open it up and close it again.

IMG_2469First, turn the focus ring until you see this tiny set screw. Remove this set screw and store it somewhere safe where you cannot lose it. These are delicate and using the wrong driver or twisting from the wrong angle could ruin the slot! I hate these things.

IMG_2470Once the set screw is removed, you can now remove the retaining ring/front ring from the rest of the lens. Be careful not to scratch the front element!

IMG_2471The objective can easily be pulled out from the lens barrel. Be careful not to drop this thing as they could free-fall into the floor by the virtue of their weight alone. You do not want to have a “Mr. Bean” moment when working with anything as delicate as these.

IMG_2472As you can see from this picture, the hole in the iris assembly leads all the way to the glass inside. This is one of the causes for the dirt accumulating in the middle elements. Lenses back in the days were not weather-sealed, this thing only came about when camera makers start to incorporate electronics more and more into their products.

IMG_2473Unscrew the (3) screws to separate the front assembly from the rear assembly. It should not take a lot of effort to take them apart and if yours felt stuck then just place a small drop of acetone into the seams and let capillary action take it into the rest of seam. Just wait for a couple of minutes to let the acetone work and you should be able to separate them with no effort at all.

Simply blow the junk away using the bulb blower and reassemble your lens again once you are satisfied. A flashlight can help you see the dust better. Just flash the lens from behind and look at the lens from an angle and they should easily be seen.


This should be an easy fix and it took me less than 30 minutes to finish mine. Putting the objective back into the lens barrel will take you some time because the insides of this lens is so cramped and there is no place to manoeuvre those big chunks of glass inside it.

Be careful on the whole process as you do not want to accidentally damage your lens. Just go about slowly and you will get there eventually. This is something that you might do on a regular basis (maintenance) so please be patient.

Thanks for reading this blog post and I hope that you have enjoyed reading this one even if this is shorter than my usual blog posts. Please keep one supporting my blog and until the 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.

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.


4 Comments (+add yours?)

  1. Trackback: Repair: Noct-Nikkor 58mm f/1.2 Ai-S | Richard Haw's Classic Nikkor Maintenance Site
  2. Trackback: Internet Nikon Repair Resources – My Take on Photography and Diving (Underwater Photography Mostly)
  3. Trackback: Articles Index | Richard Haw's Classic Nikkor Maintenance Site
  4. Trackback: World of F-mount Nikkors (1/3) | Richard Haw's Nikon Maintenance Site

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