Repair: Nikkor 28mm f/3.5 Ai-S

Hello, everybody! It is the middle of autumn but the trees here in have not reached their peak autumn colors yet! This is starting to get frustrating for me because this is the only time of the year that I can justify shooting with Fujifilm Velvia! Autumn is about the time I use my wide lenses for landscape photography and I will show you one of my favorite lenses for shooting the gorgeous colors of autumn.

Introduction:

Today’s lens is the venerable Nikkor 28mm f/3.5 Ai-S lens! It’s one of Nikon’s cheaper but better-performing lenses and you will want to shoot with it as soon as you see what this little thing can do. This lens was made from 1981-1989 and is the last of the well-loved 28/3.5 family of Nikkors that started in 1960 with the Nikkor-H•C 28m f/3.5 Auto. For many, these lenses represent a time when lens speed isn’t the only thing that matters but what the lens can do despite not having a fast maximum aperture value. People back then are less-concerned with the charts than they are today and so these lenses sold really well. Amateurs and professionals loved these lenses for their value, a very good mix of price and performance that you don’t see these days. They aren’t really dirt-cheap when they were new but they’re certainly cheaper compared to their faster siblings and that means a lot for some people.

img_2137The 28mm focal length is one of my favorites and I own many 28mm lenses. Here’s the Nikkor 28mm f/3.5 Ai-S with a Micro-Nikkor 55mm f/2.8 Ai-S. They  make for a good setup for general photography since they compliment each other well in terms of focal length and use. You can take plenty of beautiful pictures with just these 2 lenses and make a whole career out of them.

As you can see from the picture, the Nikkor 28mm f/3.5 Ai-S cannot focus all the way to infinity and stop at around 5ft only. This was the reason why this lens was sent in for repairs. The lens is otherwise near-mint despite having caked grease underneath the focusing and aperture rings. Its grease started to go bad and I just can’t let it degrade further so I’ll do a complete overhaul of the lens barrel. The optics look spotless so far and I’ll leave that alone, it doesn’t make sense to open this thing up just for fun since it’s not my lens so I will keep the repairs to a minimum if possible. Unnecessary trauma is bad for a lens so only repair what you have to.

The venerable 28mm family of F-mount lenses for has a very long and rich history. The first lens in this family is the Nikkor-H 2.8cm f/3.5 Auto and it’s one of the first Nikkors sold for the Nikon F – Nikon’s first SLR camera. The 28mm family is still being developed up to this day and most are considered to be really good lenses but none of them are slower than f/2.8.

(click to enlarge)

Sharpness seems pretty good even wide-open and if you stop the lens down to f/5.6 the image improves significantly. Flaring is a problem typical for this lens family from the start and it can be a pain since the image loses contrast in certain parts of the frame. I’m not saying that this is a bad lens because it improved significantly and the earlier versions are worse.

(click to enlarge)

Here are 2 beautiful samples shot with Fujifilm Provia 100 slide film. I really love Provia but It’s not cheap so I only shoot it occasionally. The results I get are just as good with both film and digital when using such a fine-grained film like Provia.

The photos were shot at around f/5.6-f/11 since it was reasonably bright that afternoon and it made no sense to shoot wide-open. The picture of the lady was shot at f/5.6 and if you can click on the image you’ll see that it is sharp. I can see the details of her eyeglasses’ frame and her wrinkles, too. The photo has no artistic value but I added her picture into the mix since I was happy by what I saw. It’s also worth noting that the photos have been tweaked a bit in Lightroom by adjusting exposure, contrast and white balance except for the lady’s picture which was cropped.

Having mentioned all of the above, I would still consider this to be a pretty good lens even with high resolution digital cameras. This lens is also really good when used in reverse for shooting extreme macro images.

2835aisThe optical formula for this has hardly changed since it’s debut in 1960 and the optics were only revised in the late ’70s. It is still the same 6-elements-in-6-groups layout but as you see in the illustration above the curvature and design is totally different and you can say that it is a totally new lens. It is a classic and a true testament to the optic’s design and not a lot of lenses can boast this. Owning a copy is like owning a piece of photographic history.

img_2434Here it is together with my Nikkor 85mm f/2 Ai-S lens. One for wider shots and another for tele. Both are great and they’re a joy to use.

This lens is very versatile and you can use this as a walk-around lens and if I were given an option to only choose one lens when I travel to a dangerous foreign country then the Nikkor 28mm f/3.5 Ai-S or any of its kin will be on top of my list. You can also use this lens for street photography, in fact, Joel Meyerowitz is said to like the 28mm focal length because it gives him more room to tell a better story.

img_2431Here it is with the complimentary HN-2 hood. The older lenses flared badly and contrast is not astounding (but still good). As better coatings were used by Nikon, this problem started to go away. This version is great even when shot against the Sun but a hood will always be good just-in-case. It balances really well on small but heavy cameras like the Nikkormat EL. Focusing on older film cameras can be challenging because of the darker view that the slow f/3.5 maximum aperture gives you but it’s not that bad and you will get the hang of it really quick.

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):

This lens is pretty basic. It has a lot in common with the Nikkor 85mm f/2 Ai-S when it comes to the lens barrel. It can get really tricky because there are two helicoid keys and you should align them properly. If you got it the other way around then the lens will not focus properly and you will have to open it up again. Just take lots of notes and don’t forget to take pictures and you’ll be fine. If you don’t have the proper tools then please stop now! Don’t work on this lens until you have acquired the right tools and skill so you won’t do any irreversible damage to your lens. This is not a lens for beginners.

img_2268Focus the the lens to its minimum focusing distance to reveal this set screw. Unscrew the thing carefully and store it somewhere safe so it won’t get lost or damaged.

img_2269You can now unscrew the front barrel. It can’t be remove unless the screw is gone because it secures the ring by sinking into the thread through a hole that was drilled using a pin vice, a Dremel would have been too powerful.

img_2270Unscrew these screws from the bayonet plate. If they will not come off then place some alcohol or solvent on them and wait for it to work on it before you try to remove them again. Be sure to use the weight from your elbow to apply pressure so you’ll not accidentally slip and damage the screws or the lens. If you haven’t read my article on removing bayonet screws please stop and read it now! Many people get stuck because they stripped their screws, reading my article will help you prevent this from happening.

img_2271The  bayonet should come off rather easily since there are no springs or any mechanisms that are connected to it underneath that you can accidentally damage so don’t worry.

img_2272The aperture ring comes off just like this and is not screwed to the aperture fork inside. It is good that I got to work on this before it got worse, just look at that caked grease on the chrome. It is a sign that the grease is starting to go bad. In fact, the helicoids felt a bit dry.

img_2273Carefully remove this ring. This is what couples the aperture ring to the iris mechanism in the objective’s casing. It restricts the movement of the lever that controls how much the iris should open up. Never lubricate this part, it works great just like that.

See that screw that I encircled? That screw should not even be there and it did not fall off from any of the parts inside the lens and there is not way this thing could have come from outside since it is too big.

img_2274This rogue screw is what’s keeping this lens from focusing to infinity. It is in the way of the objective’s housing’s path and the lens will not collapse to its shortest length. Its size is a hint that it belongs to a bigger lens, it is possible that this got there by accident in a workshop somewhere. It still has the seal that Nikon uses so it’s not from the factory because if it was then it has to be clean because the lacquer is applied on the screws as a sort of an indicator if a lens has been tampered, it’s also a weak thread lock. The lacquer on the screw is dry and with signs that it used to be fixed.

img_2275The helicoids has two keys to keep it in sync, remove the screws to remove the keys but be sure to mark which one should go where because the keys are broken-in to their slots and it’s best that they should be fitted back again to their respective slots during reassembly to ensure its smooth operation.

img_2276Before I removed the keys I focused the lens all the way to infinity and took the time to document its position for reference so I will know how high this thing should be as a guide that I have the helicoids in their proper position. It’s easy to get confused and swap the position of the keys because there are two of them instead of the usual one.

img_2277To remove the focusing ring, simply unscrew these 3 screws. These screws hold that brass ring in place and that brass ring acts like a kind of pressure plate to hold the focusing ring down. I know that this sounds weak but I will assure you that it’s enough and many expensive Nikkors use this, too.

img_2278The focusing ring came off easily. It wasn’t glued so you shouldn’t have any trouble. Notice that I have made a few shallow scratches to indicate where things should line-up with the infinity dot on the chrome ring. These marks are more than adequate to inform me about their alignment when the lens is set to infinity.

img_2279It’s time to separate the helicoids! do not forget to mark where the helicoids separate so you’ll know where they should mate later when you reassemble them. Check my article on working with helicoids so you won’t get stuck.

img_2280Same with the outer helicoid, don’t forget to mark the position where they separated, for this I even added another one to indicate how high it should be when it’s seated properly and is focused all the way to infinity.

This lens is annoying because the inner helicoid is milled into the objective’s casing. This also makes the objective prone to oil contamination. In fact, this one is close to having its optics contaminated with oil. It’s a very good thing that I got to it just in time! Clean them very well and apply a thicker type of grease because this lens has a short focus throw. This will help you turn the focusing ring precisely. Don’t forget to remove any residue before you apply a fresh coat so the new grease won’t get contaminated. Only apply enough grease to make it smooth, excessive grease is bad for this lens.

Disassembly (Objective):

I mentioned previously that the optics of the lens looks OK but I am going to show you another Nikkor 28mm f/3.5 Ai-S that was not so lucky since it was dripping with oil when I got it! It was a pain so I decided to take the whole thing apart except for the front elements group. I had to do this just to make sure that everything is OK and since the front elements group’s condition is fine, I just left it alone.

img_3072After cleaning the helicoid thread properly, I unscrewed the front elements assembly off. I then placed it somewhere safe and made sure that it doesn’t roll-off the table. If you check the front element assembly’s casing carefully you’ll see that it’s oily. That had to go so I cleaned it properly with Q-tips and lens tissue that were moistened with lighter fluid. I had to make sure that it is free from contaminants.

img_3074Now that the front elements assembly is stored safely, we can now work on removing all of the glass elements that are in the objective’s casing. Unscrew this retention ring with your fingers and make sure that the rear element is facing up! This retention ring is what keeps it in place so without it, the rear element will fall to the ground. If you’re really asking for it, the 4th and 5th elements will also dive straight to the floor.

img_3075Use a lens sucker to remove the rear element safely and be sure to mark the leading edge with a dot using a Sharpie. The mark does not have to be big so long as you know which way faces the front. I do this for all of the elements unless it’s obvious to me which way the element should be facing. I gave it a code by drawing snall dots that correspond to the element’s position. As an example, the 4th elements will have 4 small dots marked on its wall.

img_3076You can continue by removing this spacer that is placed in between the rear and the 5th element. Be sure to mark which side should be facing the front because if you get this wrong you’ll end up with a cracked element because the pressure from the incorrectly-mounted spacer will damage the glass.

img_3077Use a lens sucker to remove the 5th and then the 4th element and as usual, do not forget to mark their element number and direction with a Sharpie.

img_3078Here is the 4th element. Notice that it looks ambiguous so you should mark its direction. The 4th element was also drenched in oil and I had to wipe it clean with Zippo fluid and a lens tissue.

img_3079Here are the lens elements placed in their proper order. They’ll be cleaned properly and I also made sure that they are dust-free before I install these back to their casing.

That’s it for the objective. If the lenses are oily then it follows that the iris is also in a worse state so it’s time to clean the iris just in case.

Disassembly (Iris Mechanism):

The iris was soaked in oil, this affects exposure because the iris is sticking to itself. This problem is prevalent with this lens because as mentioned earlier the thread of the helicoid was milled directly to the objective’s casing.

img_3080Not a pretty sight. Before you disassemble the iris, make sure that you took enough notes or take a few pictures for reference. In this lens, there is a dot that’s left by the machinist and it corresponded to a hole on the casing – how convenient!

img_3081Now, go to the other side and remove these 2 screws. This will free the iris assembly from the objective’s casing so be careful not to drop the iris to the floor and damage it.

img_3083Carefully pick the iris assembly with a pair of tweezers while being careful not to touch any of the blades in the iris itself. These are delicately thin and they will warp easily.

img_3084It’s good that the iris assembly can be removed as a unit, that makes this a lot easier for us but before you go further you have to detach this end of the spring from a hook that can be found in the rotator plate. Use a nice pair of sharp tweezers for this and be careful not to ruin it or you’ll end up with a bent spring that looks funny and your iris won’t close properly.

img_3085Now that the spring is detached from the rotator plate, you can now remove it safely. Notice that the iris blades were kept in place by the oil and without the oil, the blades will drop to the floor so open it like this to prevent it from happening.

img_3086The oily blades were dropped into a clean sheet of tissue to cushion the fall. They are going to be wiped clean with lens tissue and lighter fluid.

Clean everything really well and reassemble the iris carefully. Never oil the iris because they should operate dry. If you have to, dust the iris with plenty of graphite powder and then blow the excess away after actuating it several times to spread the powder evenly. This will make the iris operate smoothly and it’s the only way to lubricate it safely.

Conclusion:

To make this a complete article I had to use 2 lenses to get the job done. The 1st lens has clean optics while the 2nd was dirty with oil. It all ended pretty well so I guess they’re both OK and should last for a long time.

If you have been following my blog then you’ll note the similarities between this thing’s construction and that of the Nikkor 85mm f/2 Ai-S‘s. These lenses were made around the same era so they share Nikon’s standards for small Nikkor primes. Will this be a good project for a beginner? Maybe not. You’ll have to be repairing lenses a bit longer than that before you touch this. You may not get the helicoids right or strip the screws. Just practice on a cheap junk lens from another maker first and buy all the required equipment.

img_3087After a thorough cleaning, the blades were put back into the casing. As you can see, the oil left permanent marks on some blades. This is just cosmetic and it will not affect the performance of the iris in any way so do not worry.

img_3088Install the rotator plate, be sure that the pins of the blades is in their proper slots. Make sure that it works before you proceed.

img_3089This is the tricky part. In order to save you a lot of time and trouble putting the iris mechanism back into the objective’s casing, rest the iris assembly on something that can fit into the interior of the casing. In this case, an enamel paint bottle was used. Slowly lower the objective’s casing into position and carefully put the 2 screws back to secure the iris assembly before you flip it back. Check if the iris assembly is aligned with your mark and then tighten the screws until you are satisfied that it’s secure.

img_2281Before putting the lens back together, assemble it up to the point that I have here in this picture and adjust your lens’ focus. Note that the mark lined up with the lens’ centerline perfectly and that means the helicoids are perfectly aligned. Let’s now begin adjusting. Read my article on focus calibration and follow the steps carefully.

img_2282It’s focusing again to infinity! This is certainly one of the weirdest projects that I worked on. I have never seen anything like this and I doubt that I will see anything similar. I also used a stiffer grease for this and now this thing has the correct resistance when you turn the focusing ring. It feels so good that you want to turn this thing all-day!

This is going to be tale that I’ll tell my friends for a very long time and I am sure that this story will entertain everybody who’s into photography. I hope that you liked this week’s blog post, we’ll talk about something interesting next week. Thanks for supporting this blog, Ric.

PS: Thanks to reader Keith Barefoot for his input.

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 site’s upkeep you can simply 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 will appreciate it if you leave out your name or details like your country or other information so that donations will totally be anonymous. This is a labor of love and I intend to keep it that way for as long as I can. Ric.

Advertisements

9 Comments (+add yours?)

  1. Keith Barefoot
    Nov 20, 2016 @ 20:03:50

    Hi Richard,
    Thanks, as always, for your instructive service by posting these disassembly guides.
    One note: In this one, you state that ” The optical formula for this[the 28/3.5 AiS] has hardly changed since it’s debut in 1960 and was only tweaked minimally throughout it’s very long life.”
    In reality, the optical formula changed in a major way in early 1977. The old lens was the evolution of the Nikkor-H 28/3.5, which ran from the beginning to 1977. It originally had a pentagonal iris, and despite it’s mono-coating was unusually resistant to flare from strong point light sources like the sun. Multi-coating in the early 1970’s (the .C and K era) further improved the flare performance. The present lens was an all-new design in 1977. If you are a ’28mm nut’ as I am, it is probably worth owning both, as there are fascinating differences in the look of the images they produce.

    Reply

    • richardhaw
      Nov 21, 2016 @ 00:23:33

      Hi, Keith!
      Thanks for pointing that out, I will edit it. What were the changes? it seems like the design was refined somewhat. I love the 28mm 3.5, in fact I actually own all of the Nikkor-H series. I don’t know I find that they flare more than I am comfortable with. Yes, the 5 sided iris takes a little bit of getting used to hahaha. Thanks again,Ric.

      Reply

  2. Keith Barefoot
    Nov 21, 2016 @ 03:56:41

    The old design 28/3.5 has a strong “old time”, optically primitive style of correction. If you can get one cheap, check it out.

    Reply

  3. Trackback: Internet Nikon Repair Resources – My Take on Photography and Diving (Underwater Photography Mostly)
  4. John
    Nov 26, 2016 @ 03:12:45

    Do you do repairs for other people? I’ve a 135 f2 DC that is badly fungus affected and a 50 f1.2 with some starting to show at the edges. The 135 is junk to me unless (or if) I can get fixed so I don’t mind taking a risk with it if you are willing to give it a go.
    Thanks

    Reply

    • richardhaw
      Nov 28, 2016 @ 13:49:53

      Hello, John!

      Unfortunately I rarely do repairs for other people because of my long hours at work. How bad is the fungus on the 135 anyway and how bad? AF Nikkors are a pain to work with since they are engineered like puzzles. The 50mm f/1.2 is known to attract fungus under the front element. If the growth happened under the front element then you’re in for a hard time because it seems like it is in a sealed compartment together with the 2nd element. Ric.

      Reply

  5. Trackback: Articles Index | Richard Haw's Classic Nikkor Maintenance Site
  6. Trackback: World of F-mount Nikkors (2/3) | Richard Haw's Nikon Maintenance Site

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: