Repair: Nikkor-N 24mm f/2.8 Auto

Hello, everybody! How are you guys today? I am sure that you have noticed some of my personal things creeping into this blog such as my work-related stuff. I work as an artist but I also do lots of technical stuff that’s a bit closer to engineering. There will be times that I’ll have to devise clever solutions to a problem, this is what’s keeping me sharp. I am comfortable working with both scenarios, that makes me a generalist of some sort. Speaking of being a multi-role professional and using clever gimmicks, I will showcase today an innovative lens that utilizes a really clever solution to a problem, making it flexible for more than one purpose. This lens is legendary in its own right, I shall explain to you why in this article.

Introduction:

We’ll talk about a very influential lens this time so let me have the pleasure to introduce to you the Nikkor-N 24mm f/2.8 Auto. It’s the first lens to utilize the innovative CRC (Close-Range Correction) mechanism. The CRC system is used for altering the spacing of the elements as you focus in-or-out. This is a creative and efficient concept because up until that point, most, if not all of the other lenses use simple rack-focusing wherein the objective only moves in-and-out as a single unit. With CRC, rack focusing is coupled together with another movement wherein one or more optical assemblies move closer or further in relation to the film plane to give you better results when the lens is focused up-close and the corners look better, too. In this lens’ case, CRC is used for making it achieve an impressive 0.3m minimum focusing distance. It also ensures that the image remains sharp through-out the frame at 0.3m. This was hard to achieve back in the day for a lens this wide, it also helped make this compact while giving it a reasonably-fast maximum aperture of f/2.8. Retro-focusing techniques were used on wide-angle lenses of the day, it was yet to be perfected because the technique is known to produce terrible corners at very close ranges. This is the reason why the Nikkor-H 2.8cm f/3.5 Auto only has a so-so 0.6m minimum focusing distance. CRC enabled this to overcome that since a wide-angle lens that couldn’t focus close is limited in its use. You don’t exclusively use a wide-angle lens to get things in-frame in tight spaces, this is one thing many beginners get wrong.

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The Nikkor-N 24mm f/2.8 Auto is a lovely lens. This is dense and compact, it balances really well on most cameras. This lens is also great for people who shoot videos because 24mm is pretty good for videography. You can use this for storytelling, making your subjects appear more important since they’re going to appear larger in your composition as they get closer to the camera. Of course, you can also us this to get more things inside your frame.

The CRC gimmick is widely-used on many lenses that require it and is used on the Micro-Nikkor 55mm f/2.8 Ai-S and the Micro-Nikkor 105mm f/2.8 Ai-S to name just a few. Macro-lenses benefit from it since they have to perform perfectly at high-magnifications and still required to do a good job when it comes to objects that are further into the frame. Nikon implemented it with many premium Nikkors, without CRC we won’t have legendary lenses such as the ground-breaking Nikkor-N 35mm f/1.4 Auto.

This is named Nikkor-N 24mm f/2.8 Auto because “N” stands for “nona” (or 9). There’s 9 lens elements in all and Nikon used to name their lenses using latin names for numbers to show how many elements were used. As lenses got more complicated, the element count got more and more, this practice became impractical so it was dropped. The design is a then-new 9-elements-in-7-groups one, it’s a complex lens for its time so I imagine that this was an expensive lens when it came out in 1967.

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Here it is beside the smaller Nikkor-S 35mm f/2.8 Auto. It is just a bit bigger, if you consider that the Nikkor-N 24mm f/2.8 Auto has more things going on inside you’ll appreciate all the efforts made in designing this little gem. It’s a ground-breaking lens for its time, getting this wide with an SLR lens wasn’t something easy and some lenses require you to shoot with mirror-up so it’s not easy to compose or frame your scene accurately. This, and the amazing Nikkor-UD 20mm f/3.5 Auto helped change the game.

Knowing how your lens performs is key to maximizing it. You will know its strengths and weaknesses, this will help you decide when to use this or not. These were taken from f/2.8, f/4, f/5.6 and f/8, we will see the most changes happen with these apertures and I’d imagine that people will want to shoot with this at the mentioned values. The tests aren’t scientific, they’re merely based on my observations and should be treated more as my impression of how this lens performs. I took these with my Nikon Df.

Flare and ghost resistance is pretty bad compared to later lenses with better coatings but this was what we had in 1967. See the pictures below to see it.

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These pictures should give you an idea of how it performs when it come to flare and ghost resistance. The photo to the left was shot at f/2.8, You can see that this will give you ugly artifacts when the sun is in the frame. The photo to the right was taken stopped-down, the ghosts turned into polygonal blobs but the ugly rainbow went away. This was shot with the sun just outside the frame so a hood may have been helpful here. Contrast remained relatively high which is good.

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These photos should give you an idea of how bad the distortion is. This was released in 1967 to put things in-context so I wouldn’t knock it for this but I won’t be using this for architectural photography or for things that requires accurate reproduction of lines in your scene.

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Here is another sample of the lens in real-world use. I shot this on purpose to show more lines. You’ll observe the orange line dips a bit and the awning is distorted but that is probably because I was shooting a scene with plenty of lines on purpose. If you look at the track at the bottom of the, you can see that this will give you a shallow bell-curve-type profile if you’re not careful framing the lines in your scene.

(Click to enlarge)

In real-world use, the distortion isn’t that noticeable unless you look for it or get fussy. The important part is this is sharp, contrasty and vignetting is well-controlled. I observed that it has a cooler-than-normal cast but that is normal for a lens of this vintage, the lenses made in that era were made for use with monochrome film. Many older lenses exhibit this slight, bluish tint and it only becomes an issue when shooting color film. It’s easily-fixed with white balance on digital cameras.

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Here are more examples, just frame your scene so that the straight lines are not parallel or near the edges and you’ll be fine.

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This lens is probably too-wide for general photography but it can give you interesting opportunities to play with your angles and foreshortening. This can be very useful for storytelling, that is why many cinematographers like using wider lenses to give their frame and subject a sense of where they are and how important they are to the story.

(Click to enlarge)

One of the most important features is its ability to focus really close. If you look at the bulb you can see that the filaments look sharp. The picture to the right was focused at the hen but it is a bit blurry due to my shaky hands so I missed my focus. When shooting this at 0.3m, it is easy to make your subject stand-out due to its wide angle. A little strawberry on top of a cake suddenly looks larger-than-life and its significance has been showcased. There are no strawberries on my photos but you get what I mean. This trick could also be used on wedding rings or figurines on a wedding cake. If someone told you that a 28mm and a 24mm lens is too-similar, tell them that’s not true. With a wide lens, each millimeter counts so even a 1mm difference will give you a different coverage, the effect is amplified as the lens gets wider.

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It’s nice for general photography, it’s also handy for travel photography, too. Just use this with a 50mm and 135mm lens and your kit is now complete.

This was originally designed for use with film so it’s only fair that we judge this with its intended medium. It’s difficult to simulate the look of film with a digital camera because of grain. It reacts to light differently and it’s not as reflective compared to a digital sensor so it can hide certain artifacts. I shot these with a Nikon F3 and a Nikon F4.

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I think this was shot wide-open and the focus is on the green sign. You won’t get plenty of background blur with a lens this wide but it is enough to blur some parts of it.

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This was taken at about f/5.6 using a fast shutter speed of about 1/250s with the setup mounted on a tripod. The Nikon F4’s mirror-slap is strong and you should use the mirror-up mode to prevent blurry shots like this.

You’ll want to use a faster film with it for indoor photography since f/2.8 will not be enough. The good news is you’re able to use slower shutter speeds so shooting at 1/15s is an option.

Leaning against a wall will help stabilize your setup, it took this at 1/15s and it’s still useable.

Shooting at 1/8s is probably the limit when you’re hand-holding your setup. This isn’t bad at all but you’ll want to use a faster shutter-speed as much as possible to prevent blurry photos.

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Let us now see some long-exposure pictures. These were taken using slower speeds from 2-4 seconds with it stopped-down to smaller apertures like f/8. Coma isn’t a problem at these apertures so you won’t see that here.

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Sharpness is nice so far even to the far-edges of the frame as expected. This film isn’t fine-grained but it looks nice when viewed with a large monitor. A fine-grained film is better for these kinds of photos where you will want to resolve every bit of detail.

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The sun-stars look good despite being 6-sided instead of the more-appealing 7-sided ones that’s common in most later Nikkors.

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Here are more photos that I took with film. These should help give you an idea on the potential uses of this lens. You can take photos of restaurants if that’s your thing but a lens with less distortion is probably what you’ll want to use if you’re a modern-day professional. If you’re just shooting for fun, it will give you plenty of nice photos that you can share with your friends. It’s even better if you shoot them with film since this lens works nicely with it.

I’ll say that this is still pretty good despite its age. The later versions of this lens are much better due to better coatings. The final evolution of this lens is the AF-Nikkor 24mm f/28D lens which has autofocusing capabilities while still maintaining the CRC mechanism. It’s a very good lens as well and it is a testament to how good this lens family is from the first version down to the last. Cropped-sensor camera shooters will love this because it’s closer to the classic 35mm FOV on a 1.5-crop sensor and you can use it as such. I like the 24mm focal length so this is going to be in my bag for travel and landscape photography. With that said, if you are looking for a nice sample on the net just make sure that you get one that has the Ai-ring so you can use that with newer Nikons. The non-Ai ones can damage your camera if you mount them to Nikons that only supports Ai lenses. They’re a bit more expensive but it’s important that you get the ones that have have them. People who enjoy and prefer shooting with older gear should get one, for those who just wanted a nice manual-focus equivalent then the Nikkor 24mm f/2.8 Ai-S should be an even better option, it has a new 9-elements-in-9-groups design, the coatings are better as well. That will cost you quite a bit but it’s a better lens overall.

Before We Begin:

If this is your first attempt at repairing a lens then I suggest that you check my previous posts regarding screws & driversgrease and other things. Also read what I wrote about the tools that you’ll need to fix your Nikkors.

I 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 novice. Before opening up any lens, always look for other people who have done so in Youtube or 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 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 and it will be beneficial for you to read this.

Disassembly (Lens Barrel):

Just like working with most lenses, you will want to separate the optics from the lens first in order to store it safely while you work on the rest of the lens. This lens is no exception but you will have to be a bit careful because it has a CRC unit. It’s a precise mechanism so be careful when working with it. Due to this very same reason, I will not encourage those who have no experience in repairing lenses to tackle this as their first lens. You will have to be experienced enough to work on this because of the CRC unit or at least be confident with your techniques as a repairman. You won’t need any special tools for this but you’ll want screwdrivers that will fit the slot properly or else you will risk ruining the screws. I enjoyed working with this historically significant lens and I must say that this lens really is an engineering feat back in the days for Japanese precision manufacturing.

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Remove this set screw first. This secures the front bezel of the focusing ring.

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The front part of the focusing ring can now be safely unscrewed from the focusing ring.

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Now that the bezel is gone, you can now access this small set screw that secures the front barrel to the rest of the lens. Be careful not to damage the head of the screw.

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Now that the screw is gone, you can go ahead and unscrew the front barrel.

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The objective can now be pulled out and stored in a safe place. It is very important that you pull this out carefully and not disturb the alignment of anything in the objective. This is a CRC lens lens and things are oriented in a very precise manner. If you look at my lens you can see that somebody else has scribed a line along the center of the lens. It’s a mark made for reference so that you will know how things should be oriented later when you reassemble your objective. Also not that I’m doing everything the lens is focused all the way to infinity. Always work like this so you have a reliable reference point.

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Now, on to the rear of the lens. To remove the bayonet mount, carefully unscrew these 5 minus screws. Note that the screw on the 12:00 position has been stripped by somebody else who worked on this before. It may be hard to see but you can see that it’s shiny.

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A stripped screw head can only be safely removed by using a screw extractor. Please see my guide on using a screw extractor to know how to use one. Never follow what ever you see on the internet, most of the advises given will only make the problem worse!

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The bayonet mount can now be safely removed from the rest of the lens.

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To remove the aperture ring, you will have to remove this screw. This screw serves like a pin to couple the aperture ring to a mechanism inside that’s connected to the iris.

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Next, the aperture ring is being secured by this retainer ring. You will need a spanner to remove this. See the slots that I encircled? These should tell you which tool is needed.

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It may be difficult to unscrew it off due to some gunk or glue so be careful.

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The aperture ring can now be safely removed.

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Going back to the front of the lens, remove these 3 slotted screws so you can remove the focusing ring. These screws secure the focusing ring and this is also where you should be looking at to adjust your lens’ infinity focus. These are usually secured with lacquer, glue or some thread-locking agent. Use some acetone or heat to soften whatever is there so it’s easier for you to remove these screws in case they are hard to remove.

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As mentioned in the previous step, this part is where you adjust your lens’ focusing. You will want to make a mark to help you remember how it was originally oriented so that it is going to be easier when it’s time to adjust your lens’ infinity focusing.

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This brass ring is a shim and you will never want to lose or damage this thing.

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Be sure that you don’t lose this and store this in a safe place.

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To separate the helicoids, you must first remove this decorative sleeve with the scale and grip that was beautifully machined into it. These 3 screws should be removed so that you can remove the sleeve to expose what’s concealed underneath it.

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The sleeve comes off just like this. Gunk tends to accumulate under this thing so I always make it a point to clean these parts very well before reassembly. Just look at that thing!

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With this thing still focused at infinity, scribe a line along the center to remind you that this is is how the helicoids should line-up properly. As you can see, the guy who worked on this lens previously did exactly that. This is a common practice in lens repair.

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The helicoid key on this lens is a bit different compared to other Nikkors of the same era. It’s situated at the base of the inner helicoid. The helicoid key keeps all 3 helicoids in sync as you rotate the central helicoid via the focusing ring. Without this thing you lens won’t extend or collapse because the helicoids aren’t in sync.

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Carefully remove the helicoid key by removing its 3 screws. They can may easily stripped because the screws were made with a softer type of metal so be careful. I would even use heat to soften the glue on the screws if they’re stuck before doing another attempt at it.

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Now that the helicoid key is gone, the helicoids can now freely turn. I would collapse the helicoids all the way and make a mark to remind me of their position. This will help me later determine if I got the helicoid back together properly or not.

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The helicoids can now be separated. Here’s where the outer helicoid and central helicoid separates. Always make a mark to remind you where they separated because this is also where they should mate. If you forgot to do this then you will be frustrated just guessing where they should mate. Read my article on how to work with helicoids just in case.

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Now that the outer helicoid is free, you can now dismantle it even further. Carefully pick off this brass ring so you can remove the aperture fork and its ring.

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The aperture fork and its ring couples the aperture ring to the iris assembly. You should never lubricate this part because it’s directly toughing the iris mechanism. Any oil in this will migrate to your iris eventually and will contaminate it.

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This is the fork for the CRC unit, I would remove this and clean it thoroughly just in case. Just like the aperture fork, I will avoid lubricating this part for the same reason as above.

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These set screws can be loosened to remove the adjuster ring for your helicoid stop. This ring constrains the helicoids to your focusing range. These things are usually glued so I’m going to saturate them with MEK to soften the glue before I remove it. I will work on the other parts of the lens while I wait for it to work on the glue and come back to it later.

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Here is a picture that I made to give me a hint later as to how far-in the inner helicoid is. This will help me later as I reassemble this thing together back again.

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In order for you to separate the inner helicoid from the centra helicoid, you will need to remove this helicoid stop by unscrewing these screws. Rotate the inner helicoid until you see them and carefully unscrew them using the correct-sized drivers.

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Once the helicoid stop is gone, you can now separate the inner helicoid from the central helicoid. As usual, always mark where they separate. A small mark is more than enough.

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Going back to that adjuster ring, I suppose the MEK has done its job so it’s now OK for it to be unscrewed safely. If yours don’t come off, you may need to soak this thing in a bath. I use alcohol for this and there are even times when I needed to soak this overnight just for it to come off easily. Be extremely careful not to cross-thread this part.

That’s all for the main barrel. It really isn’t too different when you compare it with usual Nikkors of the same vintage. The only noteworthy difference is the fork to drive the CRC unit. It’s amazing how Nikon kept the lens compact despite the additional engineering.

Disassembly (Objective):

The glass on my lens is clean enough so I don’t need to open it up and clean everything. It did have haze on the central block but that was easily taken cared off before it made any permanent damage to the coating. That most likely came from the evaporating grease at the CRC unit’s helicoids. If you need to open everything up to give it a thorough cleaning, I’m sorry but I cannot help you in this guide. Except for the CRC unit, the objective is the same as most Nikkor lenses so if you have been following my blog then I’m sure that you are already familiar with this and you can find your way around this without a guide.

Remember to always take notes before you remove anything. Take measurements of the CRC unit’s tolerances before you proceed and never forget to mark where and how they separated when working with its helicoids. Remember, this is precision engineering!

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Here is the objective. Be very careful while working with this because of the a CRC unit. It is important that you take notes and measurements before you remove anything in this. I want you to see the small tab near the rear end of the objective just below the scar made during machining. That tab’s connected to the fork on the inner helicoid. Putting this lens back together can be a pain because you will have to line this up properly with the fork.

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The CRC unit on this lens is a rear-focusing type. It has a helicoid that allows the rear to move as you focus in or out, altering the geometry of the lens formula and just like any helicoid you will need to mark where they separate. Be careful not to scratch your glass as you go about working on this thing. Only lightly lubricate this with a thin grease or the grease will migrate to the glass. A thin film of grease is more than enough for this part.

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Clean The lens and helicoids properly. The inner elements can be accessed by using a tool with prongs such as a spanner to unscrew its housing off from the objective’s casing.

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The front elements can be removed by unscrewing it off. Mine was clean so I didn’t have to open it up. If you needed to open yours up, don’t worry because it’s of a conventional design. If you’re experienced with working on Nikkors, this should be easy for you.

That’s all for the objective. As long as you are careful with the CRC unit everything should be fine. This is Nikon’s first CRC lens so I guess that the engineers were conservative with implementation so thankfully nothing that is extraordinarily weird can be found here.

Conclusion:

That’s it for the disassembly! It’s now time to put everything back together. Just follow all of the steps in reverse and backtrack or at least that is the general rule. I will use a heavy grease for the helicoids and then simply dab a very thin film of grease for the CRC unit’s helicoids. Remember never to put too much grease on the CRC unit’s helicoids, it will just create a mess and will cake-up eventually. In colder weather, your lens may even seize if you lubricate this part too much. Fortunately for us, the helicoids on this lens has a much shorter throw compared to the Micro-Nikkor 55mm f/2.8 Ai-S. The short focusing range of this lens allows for the use of a heavier type of grease and the CRC unit only has a single set of helicoids so it isn’t going to be too stiff. The Micro-Nikkor 55mm f/2.8 Ai-S has plenty of helicoids and using a heavier grease on that lens will make it difficult to turn.

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The person who worked on this lens prior to me had the common sense to scribe a mark to remind him of the lens’ correct orientation, this helped me a lot and removed plenty of guesswork. Normally, I would rebuild a lens and then insert the objective into the barrel in the same manner you pulled it in the earlier steps while carefully making sure all the tabs in the iris line up to their respective forks. This is a bit different because it has a 3rd tab for the CRC unit (at 10:00) so I left out the bayonet mount until the objective is safely reinstalled into the barrel like in this picture. I made sure that things are all in their right orientation then I carefully reinstalled the bayonet mount.

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It’s now time to calibrate our lens for infinity focusing! Read my guide to make it easy for you to do this if you’re a beginner. If you recall it, this ring is where you adjust your lens’ focusing range. Make sure that the lens is focused to infinity and you have done what the infinity calibration guide said and then carefully adjust this ring so that the helicoid stop is in contact with it. This will give you a hard stop at infinity meaning the lens will not go further than infinity when you turn it. Check your infinity focusing again and see if there is nothing wrong. If your infinity focusing is off then calibrate it again. If you’re satisfied with the results at infinity, you can then tighten the screws to secure the ring. If want this to be really secure, you can dab a very small amount of nail polish on the seams and the screws. Make sure that the nail polish doesn’t overflow and wait for it to cure before you proceed or you will make a mess or worse, contaminate the freshly-applied grease.

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Finally, you can then adjust the focusing ring and make sure that the infinity sign and the black line are squarely aligned. Tighten all the screws once you’re satisfied and then test your infinity focusing again. It should be OK because we did that in the previous step but you want to do another round just to be sure and this time for the focusing ring’s sake. I then reinstalled the front barrel and the other parts to complete the lens.

That’s all for this post! Thank you very much for your support! Last month, we almost hit 23,000 views! We can if I published something a few days ago but I was busy looking for a new job. I hope that this will be stable and my next goal is to reach 50,000 views in the coming year! Maintaining this blog is hard work and it is not easy for just one person to do this on his free-time but seeing the stats grow make me really happy. The “beers” that you buy for me by donating to my paypal is also a bonus. It keeps the site alive and it also helps me buy “beer” and film. OK, I don’t drink bear because of gout so I drink gin or buy film with your donation. Mostly, I just use it to pay for hosting, buying diapers at Amazon or for buying lunch. I know it sounds mundane but that’s how it is. Thank you guys again and see you guys next time! If you enjoyed this then please share it with your friends at social media or join our facebook page “Classic Nikon Maintenance”. See you, Ric.

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14 Comments (+add yours?)

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  4. Witono
    Feb 20, 2018 @ 15:58:54

    Dear Richard, thank you for sharing this guide, I had some trouble with my Nikkor-N 35mm 1.4, from noticing the similar barrel design I decided to give it a try with your guide, and I realized the construction is almost exactly similar. I fixed my lens by following your guide, thank you.

    Reply

  5. Béni
    Sep 05, 2018 @ 11:33:54

    Hello Richard and thank your for this tutorial.
    I have the exact same lens, and while I was using it the focus got really hard and now is completely stuck at about 5 m (I wanted to service this lens because the focus was grainy, you could feel that the grease was long gone… Too bad it stucks before).
    What would you recommand to unstuck it? Is that even possible without ruining the helicoid?

    Reply

    • richardhaw
      Sep 16, 2018 @ 22:33:52

      Hello. Glad you liked it. That certainly needs an overhaul. it’s not an easy lens to work on so I suggest that you send it to a repairman. There are 2 sets of helicoids there and what you are feeling may come from the inner CRC one. Ric.

      Reply

      • Benoit Masson-Bedeau
        Sep 17, 2018 @ 04:30:58

        I also have the 24 mm f/2.8 Ai-S in perfectly working order so going to the repairman and pay probably $150+ for this lens is not planned at the moment :D. I managed to extract the optical block and you were correct: this is indeed the CRC helicoid that is stuck.

      • richardhaw
        Sep 25, 2018 @ 00:51:20

        Hello. $150 for a complete overhaul? I usually charge $100 or so for a complete overhaul of a lens in that class (with CRC). I can understand if he would ask that much since CRC lenses are a bit more complicated. Make sure you take photos before you send it so you will know if the lens was set properly when you get it back. Ric.

      • Benoit Masson-Bedeau
        Sep 25, 2018 @ 19:48:53

        Tonight I put the objective in the oven at 100 °C for 20 mn; I was able to unstuck the back helicoid without damage. The doublets don’t seem to have separated from the heat so that’s a good news. I’m lucky enough that all the marking for infinity on the back elements were already there. Now to overhaul this lens!

  6. Benoit Masson-Bedeau
    Sep 25, 2018 @ 05:59:39

    Indeed $150 seems high; last year I went for regreasing 2 Nikon lenses that had a stiff focus, I payed 100 € (approx. $120). I supposed that for something that is stuck, the time and price would be higher.

    Reply

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  8. Greg Naylor
    Apr 20, 2019 @ 06:23:44

    Hello Richard,
    Just finished an overhaul on my 24mm N.C. and thought a minor variation from the earlier N might save tearing some hair out (as I did!).
    When removing the front barrel to release the optic block, where the grub screw is on the N there is only a hole on the later one, which can easily be thought of as a solvent hole to release their glue. But no, they decided to put a tiny set screw on the INSIDE of the barrel, which is made visible after removing the bezel and name ring. No amount of effort (or cursing) will release the barrel on the later version without finding this sneaky little set screw.
    Kind regards
    Greg
    Australia

    Reply

  9. Trackback: Repair: Nikkor 24mm f/2.8 Ai-S | Richard Haw's Classic Nikon Repair and Review
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