Repair: Nikkor 50mm f/1.2 Ai-S

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.

The following pictures were shot using Fujifilm Natura 1600 with the Nikon F4. I got them from the lab scanned so the quality may not be the best, I suspect that these are just 6MP images and I lost plenty of details that were otherwise clear on the negatives. Please view them to see what this lens is capable of doing.

(Click to enlarge)

Check the pictures above for some distortion-related samples. The pictures shot with this lens has plenty of distortion, I would say that this was unexpected since lenses from this class usually have lower-than-average distortion. It can be annoying if you have lines at the far-edges of the frame and see them curved.

FH000009The lens is more than capable of producing sharp images. This was shot at f/2.8 or so and I love how the negative looks like under a magnifier. It also produces nice sun-stars and I can’t believe that it did it at such a big aperture, I swear that I shot this at about f/2 – f/2.8.

(Click to enlarge)

It was difficult to focus this lens given that my subjects never stood-still for me and I was using a waist-level finder but you can take sharp pictures with this lens even wide-open or at least faster than f/2 or so. This lens is capable of producing 3D-like pictures and the rendering is very smooth and refined.

FH000006I was focusing on the noodles being shredded but the cook looked my way and smiled. It was a disaster because the framing and candid feel of this scene is now gone. If you look at the noodle and the board you can see just how nice and sharp this lens is. Look at the background and you will notice just how smooth everything is, the rendering is exquisite to say the least and this will make you want to shoot this lens at f/1.2 despite the difficulty in focusing this lens with such at aperture! Framing and recomposing can also be tricky with this lens because of the paper-thin plane of focus but that’s the best thing we can do if we want precise focusing when using a camera with a split-prism.

(Click to enlarge)

Here are some more examples, this lens just begs to be used at night. While sharpness is excellent, you can notice some magenta cast on white-colored objects that aren’t focused and just before or behind your focus plane (maybe within 3m?). This is gets less obvious as you stop the lens down to something slower than f/2 so if you absolutely want a clean picture then just shoot it from f/2 and above. You can otherwise use this to your creative effect if you wish to do so as it adds the “dreaminess” factor to your image. This can also make the skin “bloom” and will be nice for portraits. People who complain about this just don’t know how to use this effect to their advantage. This is the reason why people shoot more and more with older lenses these days because these optical flaws bring so much to an image and it makes them unique in some way.

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.


6 Comments (+add yours?)

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