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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 like my work-related things. I work as a creative but I also do lots of technical stuff that is a bit closer to engineering. There will be times that I will have to devise a clever solution to a problem and this is what’s keeping me up in my game. Being both a creative and technical person, I’m comfortable working in both scenarios and that makes me a generalist of some sort. Speaking of being multi-role and using clever gimmicks, I will now showcase to you a very innovative lens that utilizes a very clever solution to a problem, making it flexible for more than one purpose.

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 lens! The Nikkor-N 24mm f/2.8 Auto is the first lens to introduce 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 this lens, most if not all lenses use simple rack-focusing  wherein the objective only moves in and out. In a CRC lens, rack focusing is coupled with another movement wherein one or more lens elements groups move closer or further in relation to the film plane to correct for some optical flaws. In the case of this lens, CRC is in-charge of making this lens 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 and it also helped make the lens compact while giving it a reasonably-fast f/2.8 maximum aperture. Retro-focusing techniques was used on wide-angle lenses of the day and it was yet to be perfected because the technique is known to produce terrible corners at very close ranges. This was the main reason why the then-amazing Nikkor-H 2.8cm f/3.5 Auto lens only has a so-so 0.6m minimum focusing distance. CRC enabled this lens to master that because a wide-angle lens that can’t focus really close is limited when it came to creative use. You just don’t use a wide-angle lens to get things in-frame in tight spaces, this is one thing many beginners get wrong.

IMG_5763.JPGThe Nikkor-N 24mm f/2.8 Auto is such a lovely lens. It’s dense and compact so it balances really well on most cameras. This lens is also great for people who shoot videos because 24mm is pretty good for videography to help give your composition some depth. You can use this for storytelling or simply to showcase a subject in your story.

The CRC gimmick is widely-used on many lenses that require it and is used on lenses like  the Micro-Nikkor 55mm f/2.8 Ai-S and the Micro-Nikkor 105mm f/2.8 Ai-S. All macro lenses were calculated to give you great image quality at high magnification and CRC helps with that because the lens can also give you fairly good performance while focusing at infinity or just something further in the frame, making the lens more useful for general use. Jets that have variable-geometry wing design makes them good at sub-sonic and supersonic speeds because they can alter the sweep angle of the wings. This is the same concept for CRC it’s just that lens elements’ spacing are altered instead. Without CRC, we won’t have legendary lenses such as the ground-breaking Nikkor-N 35mm f/1.4 Auto lens.

IMG_2577.JPGHere is the Nikkor-N 24mm f/2.8 Auto beside the smaller Nikkor-S 35mm f/2.8 Auto lens. It is just a bit bigger but if you consider that the Nikkor-N 24mm f/2.8 Auto has more things going on inside you will appreciate all the effort made in designing this little lens.

The lens 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 on the design. As lenses get more complicated so the element count got more and more, this practice became impractical.

I did some simple tests with this lens and you will see how good this lens is all the way to the corners. Vignetting is also pretty well-controlled and distortion isn’t distracting at all. Flare and ghosting isn’t too bad as well but it’s pretty bad compared to later lenses that’s coated with better coating but it’s still not so bad and you can even use it creatively. See the sample picture below to see what I am talking about.

 

(Click to enlarge)

These 2 pictures should give you an idea on how the Nikkor-N 24mm f/2.8 Auto performs when it come to flare and ghost resistance. The picture to the left was shot at f/2.8 and as you can see that the Nikkor-N 24mm f/2.8 Auto will give you ugly artifacts when the sun is in the frame. The picture to the right was shot stopped-down. The ghosts “solidified” into polygonal blobs and the ugly rainbow went away. This was shot with the sun just outside the frame so a hood may have been helpful here. It’s really nice and contrasty otherwise.

 

(Click to enlarge)

Here’s some samples for distortion. Barrel distortion is expected due to the wide angle of this lens and you can see it in the shutters on the left picture. It’s not terrible but it’s also not that much of a big deal considering that this lens was introduced around 1967. You’ll want to use another lens for careful architectural photos if distortion bothers you. To my taste, this doesn’t bother me at all specially if you use the lens to shoot more “organic” or “practical” photos like the picture to the right. I will even dare to claim that a little bit of distortion adds to the “organic” feel of a picture, making it look more natural.

HAW_9293Here is another sample of the lens in real-world use. I shot this on purpose to show more lines in the picture. You will notice the orange line dips a bit and the awning of the roof is a bit 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 frame, you will notice that the lens will give you a bit of a bell curve-type distortion if you’re not careful framing your lines.

 

(Click to enlarge)

In real-world use, the distortion isn’t really all that much noticeable unless you look for it and get fussy. Remember that this is all we had back in the ’60s! The most important part is that the lens is sharp, contrasty and vignetting is well-controlled. I also noticed that the lens has a cooler than normal cast but that’s normal for a lens of this vintage because the lenses made in this ear were calculated for monochrome film. Many older lenses exhibit this slight bluish tint and it only becomes an issue when shooting colour film. It’s easily fixed with white balance on digital cameras. To be frank, I like a cooler tint to my images.

 

(Click to enlarge)

For general photography, this is probably too wide for that but it will give you interesting opportunities to play with your angles and use of foreshortening. This will 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 aspects of this lens is its ability to focus really close. Here are some samples when the lens is shot really close to the subject. If you look at the electric bulb you can see that the filaments look sharp. The picture to the right I was focusing at the hen but it is a bit blurry due to shake and missed focus. When shooting at 0.3m, it is very easy to make your subjects standout due to the wider 24mm angle. A strawberry on a cake suddenly looks larger than life and its significance has been showcased. Ok, There are no strawberries on my photos but you get what I mean. This trick can also be used on  wedding rings and figurines on a wedding cake. If somebody told you that a 28mm and a 24mm lens is too similar you might as well use either one for something then tell them it is not true! Now you know what’s different and you can use that knowledge to choose a focal length to compliment your storytelling and composition. As far as wide lenses are concerned, every “mm” counts as you get wider, just ask any landscape photographer!

(Click to enlarge)

By now I am sure that most of you know that I am not much for shooting grids and detail shots for pixel-peeping so here are more samples of the lens used in real-world scenarios and as you can see, the distortion really isn’t something that’s obvious.

(Click to enlarge)

Here are more samples, this time for general photography. The lens is definitely too wide for street photography where 28mm is probably the widest that you will want to use. It’s not that bad at all but that means that you should even get closer to your subject. This is also a chance because wide lenses enables you to shoot people at the periphery of your lens, your subject will think that you are shooting something else when in fact you are actually shooting him/her. If you can get close enough then that’s probably OK.

For all intents and purposes, I will say that this lens is still pretty good despite its age. It’s still a pretty good performer despite having older coating technology. The later versions of this lens are much better due to better coatings and if I’m not mistaken, the optics had been redesigned. 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 to the last one. Cropped-sensor camera shooters will love this lens because it’s akin to the classic 35mm FOV and you can use it in such a manner. I love the 24mm FOV and this is going to be in my bag for travel and landscape photography, I just love shooting this with a film camera. My monochrome film images look really sharp and contrasty.

That’s it for the introduction! Let’s now continue to the main article!

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):

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.

IMG_2881Remove this set screw first. This secures the front bezel of the focusing ring.

IMG_2882The front part of the focusing ring can now be safely unscrewed from the focusing ring.

IMG_2883Now 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.

IMG_2884Now that the screw is gone, you can go ahead and unscrew the front barrel.

IMG_2885The 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.

IMG_2890Now, 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.

IMG_2891A 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!

IMG_2892The bayonet mount can now be safely removed from the rest of the lens.

IMG_2893To 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.

IMG_2894Next, 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.

IMG_2895It may be difficult to unscrew it off due to some gunk or glue so be careful.

IMG_2896The aperture ring can now be safely removed.

IMG_2897Going 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.

IMG_2898As 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.

IMG_2886This brass ring is a shim and you will never want to lose or damage this thing.

IMG_2899Be sure that you don’t lose this and store this in a safe place.

IMG_2900To 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.

IMG_2901The 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!

IMG_2903With 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.

IMG_2902The 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.

IMG_2904Carefully 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.

IMG_2905Now 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.

IMG_2906The 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.

IMG_2907Now 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.

IMG_2908The 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.

IMG_2909This 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.

IMG_2910These 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.

IMG_2912Here 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.

IMG_2913In 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.

IMG_2914Once 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.

IMG_2915Going 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!

IMG_2917Here 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.

IMG_2918The 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.

IMG_2919Clean 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.

IMG_2920The 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.

IMG_2921The 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.

IMG_2922It’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.

IMG_2923Finally, 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.

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.

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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  1. Trackback: Internet Nikon Repair Resources – My Take on Photography and Diving (Underwater Photography Mostly)

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