Repair: Zoom-Nikkor 100-300mm f/5.6 Ai-S

Hello, everybody! It is beginning to get cold here and it’s now time to shoot pictures of migratory birds. Birding has never been my thing because of its high-cost in terms of equipment, it’s very demanding to your body and also to your pocket. A professional-grade camera is required along with a heavy, long and fast lens with the best autofocus performance. These are above my paygrade. However, you could still enjoy shooting photos of birds even with a budget if you can live without autofocus and a fast maximum aperture for your lens. There are many options out there today and I’m going to show an interesting alternative to you, read this article to know what this is.


The Zoom-Nikkor 100-300mm f/5.6 Ai-S was sold from 1984 t0 1998, it has an unusually-long production span for a Zoom-Nikkor of the period since a lot of its contemporaries were soon replaced with autofocus versions. This did not get any upgrades or successors, it remains to be the only lens of its class as far as Nikkors are concerned. It was highly-regarded by a lot of people in its day and I’ve even heard of people using this during the digital age when lenses with advanced features are the norm and I’m referring to the period between the late 1990s to the mid-2000s.

Handling is kind of awkward, it’s long, heavy and the focus-throw is rather long. It’s difficult to turn the aperture ring and manipulate the focusing and zoom barrel at the same time with one hand since the distance between the barrel and the aperture ring is quite a far. It doesn’t balance well with most Nikons, even ones with a hug body, the setup always feels front-heavy. Your mileage may vary.

It has a 14-elements-in-10-groups design which is amazingly quite simple, I would think that it would require more glass to achieve something like this but Nikon did it. What’s astonishing about this lens is it has a constant f/5.6 maximum aperture combined with a long 100-300mm focal-range but this lens’ barrel is till kept to a size that’s practical despite being huge. This is an amazing feat since it’s just around 1.3x the total size of the Zoom-Nikkor 80-200mm f/4 Ai-S.

The barrel is beautiful, it has engravings that’s typical of Nikkors from the same era. It’s a “pumper-zoom” which means that you could easily focus or zoom with it using a single hand. This makes it useful for action and sports, some people like this feature while some people don’t, it’s a really personal thing. The constant maximum aperture speed is useful for cameras that do not communicate with the lens, manual Nikon shooters benefit from this. It was probably made for professionals since this is one of the features of any higher-end lenses. I imagine that this costed a small fortune back then. This is a nice lens for shooting out-of-town, it’s relatively compact for its range, it also does the job of several prime lenses, too. I think that it’s probably a tad too-slow for bird photography but it’s just-right for outdoor events. Football, volleyball, racing and similar sports could be covered efficiently by it. Even the nefarious perverts at the beach will love it.

It’s important to study how a lens performs, you will know when to use it or when to leave it inside the cabinet. This knowledge will help you maximize its strengths and you can workaround its weaknesses, too. I do not do tests like the ones you see elsewhere, all I do is shoot a series of photos and give you my impressions based on what I observed. I value this over charts and other artificial tests since this I could study a lens closer to its intended use. I took these photos from f/5.6, f/8 and f/11 since you’ll see the most changes with these apertures. I also assume that people will want to shoot with it at these values, too. It’s too-slow so I don’t think many people would even use it beyond f/8. Some of the photos were heavily-cropped at the center so you could see the results better. I shot these with a Nikon Df.

(Click to enlarge)

Vignetting is quite bad wide-open but it’s not going to be really obvious, its falloff is rather shallow which helps mask it a lot. Stopping this down to f/8 helps alleviate much it it and you’ll only see traces of it at the far-corners. I will say that it’s as-good-as-gone at this point. You won’t see it anymore by f/11. This isn’t so much of an issue as you could see from the pictures of the sky. Distortion is well-controlled, moderate barrel-type distortion is visible at the wide-end. The longer-end exhibits minor pincushion-type distortion which isn’t really noticeable in most cases.

The following photos shows the originals (left) and the cropped versions to their right. This will allow you to examine the results better, please click on the thumbnails to see the cropped version. I heavily-cropped them so you’ll see the details better.

(Click to enlarge)

Chromatic aberration is quite high on overblown areas, it won’t go away at all even by f/11 on severe cases. This is probably its biggest weakness, this is quite terrible and it’s sometimes difficult to avoid it. You won’t see much of it by f/11 but it’s still there which is bothersome.

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Flare and ghost resistance is quite good considering that it has lots of glass. I think these are some of the best results I have seen from an older Nikkor.

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The smoothness of the bokeh is quite nice, I wasn’t able to get any artifacts, at least ones that I could notice and make an issue with. It is safe to assume that it delivers in this department.

(Click to enlarge)

These were taken using its “macro-mode” gimmick, at this setting you could focus as close as 0.7m which is quite close. Even if you could only use this at the 100mm end, it’s able to give you high-magnification which is impressive if you ask me. This is really sharp wide-open but the resolution is not quite there to support it. I’m not saying that its resolution is inadequate, it’s there but it just needs a little push by stopping it down to f/8. Stopping it down to f/8 brings the center close to peak performance. It looks quite nice by f/11, if sharpness and detail counts you should shoot it at this distance from f/8. It’s a long, heavy lens and the aperture is not fast at all so it can be challenging to shoot it at this distance without a flash.

(Click to enlarge)

These were shot at moderate distances, it’s not bad at all. In fact, it is sharp wide-open but it still has room for improvement. Stopping this down helps a lot and the improved resolution could now support the sharpness better. The corners look nicer but will only look good by f/11. Spherical aberration can be observed even at f/11 which is a shame but it’s not terrible at all and and you’ll only notice traces of it depending on the situation. It’s something that I could still tolerate unlike its high amount of chromatic aberration.

The following photos shows the originals (left) and the cropped versions to their right. This will allow you to examine the results better, please click on the thumbnails to see the cropped version. I heavily-cropped them so you’ll see the details better.

(Click to enlarge)

These were taken with it focused on objects that are further into the frame. Sharpness degrades as you focus it further and you couldn’t compare this to its performance when focused at closer distances. It improves by f/8 and its going to get a bit better by f/11 but it just doesn’t cut it, which is a shame. It would have been such a formidable lens if this could keep its performance equal at either end. This may be isolated to my sample so please do not take my observations as the absolute truth.

It renders beautiful photos that look more-modern compared to other older Ai-S lenses. I don’t know what made me say that but that’s what got into my mind when I saw the results.

Sharpness is adequate wide-open but it could be better. It can be difficult to focus since the maximum aperture is quite slow which means that you will not get enough depth-of-field to isolate your subjects. Using a split-prism is not the best way to work with it as it will get dark easily due to lack of light.

The bokeh characteristics is quite nice, couple that with its decent sharpness wide-open and it makes for a nice lens for outdoor sports and events. It just requires enough light or else it will be difficult to focus and even harder to get sharp photos since you’ll need fast shutter-speeds to compensate for its lack of brightness and long focal length.

Focusing it can be challenging since you’re dealing with a long lens. This is a problem and it could lead to some missed-shots. The focus-throw is long but it can’t be helped and that’s also one reason that makes this clumsy for use with events or anything that moves fast unless you anticipate your subjects’ movements by pre-focusing.

The character of the bokeh looks a bit clumpy at the trees, this is the worst I have seen so far from this lens.

This is how nice it could be wide-open, the background turns into a wash of color like an old Chinese painting. You’ll see traces of spherical aberration, I like it a lot in this photo since it helps give the skin a subtle “glow”.

This would have been a better photo if the shutter was faster. This is going to be something that you will learn to live with when shooting with it.

You’re rewarded with nice, sharp photos as long as you could maintain the shutter’s speed to something above 1/500s for moving subjects. Her skin has a nice glow, this lens could render people nicely.

(Click to enlarge)

Here are more photos showing how it performs with a digital camera. This is quite an enjoyable lens to shoot with despite its rather poor handling. It’s a great lens so long as you have adequate light. I think that this will still be a nice lens to use in the years to come, specially if you do not have the budget for a more expensive one. I always say that a lens’ price doesn’t matter but I will digress this time, autofocus and VR are going to be important the longer a lens gets, this is where you could justify the prices of the latest zooms.

Let’s now see some photos that were shot with film. It’s difficult to simulate how film looks with film because of grain. It helps hide or amplify flaws, it reacts differently to light so the photos it produces look different. This zoom was made to be shot using film so it is only fair to judge it with its intended medium. Let’s see if it indeed performs better with it.

This lens performs really well with film, its able to give you sharp and nice photos even wide-open, much better than it could with a digital camera. It’s probably thanks to the size of the grain or how it interacts with light, giving you the illusion of better sharpness.

Spherical aberration works really well here as it made her wig look better. I love how it made this scene look more vibrant. It was bright that afternoon so I could shoot this to its potential.

This renders skin quite well, it’s sharp but not so much as to make skin look like stucco. The rendering looks delicate, resulting in natural-looking tones.

It’s wasn’t easy to focus on gyrating samba queens with this lens since it has quite a long focus-throw. It’s a double-edged sword, you could make precise adjustments with it but it could also mean losing a shot since you could not turn the focusing ring fast enough to focus on your subjects.

Spherical aberration worked really well with this photo, it made the glow at at the plastic mic’s head look better, this photo would have been boring if it wasn’t rendered like this. You sometimes have to embrace a lens’ flaws, it’s the only way you could appreciate older lenses and what they stand for.

Chromatic aberration is quite high on the necklace but it’s not as bas as the ones we saw earlier in this article. Of course, it’s sharp as you can see how nice the strands of her hair was rendered but it’s not too-sharp as make the strands look artificial.

(Click to enlarge)

Here are more photos that I took that afternoon. This is a great lens if you’re shooting events or sports so long as it’s a sunny day. It’s able to deliver good photos wide-open and stopping it down a bit makes it even better. I love its performance with film and I highly recommend shooting this with it. This is the only way to give it a fair chance.

Film shooters will love this a lot, people who shoot with digital cameras will find this lacking in some ways and there are better alternatives out there. It is important to consider that you could get great lenses these days with lots of convenient features such as autofocus and VR for not a lot of money. The added features alone will make a huge difference since this is a long lens. It can be difficult to shoot with this hand-held let alone without VR. A Nikon Z series camera could alleviate the need for VR but that will cost you. If your camera doesn’t support the latest technologies then this lens will be useful for you. There aren’t a lot of alternatives since this is the Nikkor of its kind, the only lenses that could match this are the cheap and early AF-Nikkors, I don’t recall any of them having the same range and none of them have the useful non-variable maximum aperture feature that this one has. If you’re looking for one of these, make sure that the barrels operate properly, turn them and they should turn smoothly without any bumps. Zoom-creep is a problem but I don’t think you could find one without it. Some lenses do it more than the rest so just find one that still has a bit more resistance. This lens also has the tendency to accumulate junk in the optics since air blows in-and-out of it freely so it’s not uncommon to find one with bits of dust in the central elements. These are inexpensive at all, if you found one with all the things that you need and the price is right, just get it and enjoy using it. This lens will serve you well if you enjoy shooting with manual lenses.

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 has one of the most complicated barrel construction I have seen in a Zoom-Nikkor from the 1980s. This means it takes more time to service this lens and even more time putting things back. Carefully note the alignments of the parts and their positions in relation to landmarks. This will help you during reassembly. Never attempt repairing it if you’re a novice, send yours to a qualified repairman.

Run a thin, rounded rod underneath the huge rubber grip to lift it from the adhesive while being careful not to rip it.

Lift the rubber and unscrew these.

It’s tough to remove the rubber grip safely but you can do it. There’s a safer way to do this which involves remove the lower part of the focusing barrel first but it would’ve taken me more steps just to show it. The rubber part is old and can easily-tear if you are not careful.

The screws you see here can be removed in order to remove the scale, get it off and the rubber grip could be safely removed without it.

Here’s another screw.

Carefully remove this brass strip covering the slot of the roller.

Here’s another one.

Before going any further, make a small mark so you’ll have a guide later. It will help you determine if things were aligned properly during reassembly.

Don’t forget to note the positions of these screws since this is where you are able to adjust the distance scale.

Extract these rollers carefully. Avoid heating them, use alcohol to soften the thread-lock. The nylon bushing is delicate.

Here’s how it looks like.

Carefully extract this set screw. These are usually sealed so dissolve it using a drop of solvent.

Place a drop of alcohol into this hole to soften the seal of the front ring.

Unscrew the front ring with the help of a rubber sheet to help you grip it.

Remove the zoom/focusing-barrel.

The felt lining is worn, always make it a point to replace these.

Carefully separate the front barrel from the rest of the main barrel and do not forget to note where it separated since this is also where it should mate. Many people forget this and end up getting frustrated trying to guess where these should mesh. To prevent this from happening to you, read my article on how to work with helicoids and follow it.

Carefully extract the front elements assembly with a lens spanner. You will have to place the bits of your spanner at the slots closest to the edge and not the inner one since those are for the front element.

Extract this and store it in a safe place.

Carefully extract this optical assembly with your lens spanner.

Pick it off and store it in a safe place.

Extract these screws to remove the bayonet mount. Many people strip these because they’re not using the correct type of drivers or didn’t have the right skills. Read my article on how to remove bayonet screws to prevent it from happening to you.

The bayonet mount can be easily removed since nothing is attached to it.

Study how the mechanisms here work before you remove anything.

Be careful when removing the aperture ring, there’s a tiny ball here and it’s spring-loaded. The little parts here can be misplaced quite easily. Clean this part carefully.

Extract these to remove the chrome grip.

Carefully remove the grip. It may be stuck at times and all you will need is a little bit of alcohol to loosen it.

You can now remove the distance scale.

Extract these so you could remove the sleeve.

It has a beautiful and useful depth-of-field scale engraved on it. Use a brush to scrub this well but be careful not to peel the paint off.

These screws secure the whole barrel to the base plate. You loosen these to adjust the rear-focus of the lens. The brass shims help but it’s sometimes not going to be enough and micro-adjustments will still have to be done.

Make a mark so you will know how things should align.

One of the screws here was stripped and only a screw extractor will get this off safely. Read my article about screws to know how this is done.

Remove the base and set it aside.

Carefully remove the shims and be careful not to damage these.

Use a lens spanner with long bits to reach these slots. It was sealed so you’ll need to dissolve it with acetone.

Carefully unscrew the rear optical assembly and store it in a safe place.

Extract these screws.

Carefully remove this assembly. It houses the iris mechanism and other lens elements.

Turn the barrel to reveal these and extract them.

Here’s another set.

You’re now able to remove the inner barrel.

There’s a screw here which you could only access with this port hole.

Insert your driver inside of that port hole and carefully extract the screw.

Here they are now. Heating these will make these easier to remove.

Carefully extract these to remove the guide. Heat these and it will be easier for you to remove them.

Separate the lower barrel.

Not that there’s a few nuts here inside of their rails, do not misplace them.

Here’s another one.

Carefully extract these rollers, avoid heating them or using strong solvents.

Pick these off with a pair of sharp tweezers once they are loose.

Here’s another one.

Carefully remove this gasket. It’s made from rubber and it’s easily-damaged so be careful while you remove it. Do not soak this in alcohol for a long time or it will dissolve into nothing.

Remove the inner cam. The rubber gasket was in the way so you could not get it off unless the gasket is out of the way.

Carefully remove the floating element and its housing.

There’s another optical assembly here which you could remove using a lens spanner. Be careful not to scratch the glass while doing it.

The stop-down mechanism is quite complex. I wouldn’t dismantle this since it was adjusted at the factory.

You could remove the stop-down lever if you wish, just insert a screwdriver through its access hole and extract its screw.

Clean everything carefully, scrub the parts with strong detergent. Make sure that you leave no residue. Apply grease with more resistance, this will make it smoother-to-turn. Too-much resistance is not good either so be sure not to use super-thick grease. Only apply a thin film, that’s all you’ll need. Any part that comes into contact with another has to be lubricated with a super-thin film of grease. Anything close to the optics should never be lubricated since excessive oil will migrate towards the optics eventually.

Disassembly (Optics):

The optics are of conventional design and shouldn’t be difficult to remove if you have the right tools and skills. There are lots of elements in its design, it is best to mark the walls of the groups with a permanent marker. Use a dot to indicate the leading edge of a group and several smaller dots to indicate a group’s order. This will help you put things back properly and save you lots of time. The rear optical assembly is very delicate, avoid dismantling this as much as possible, if you got its alignment wrong by a bit that will affect how this lens performs. I won’t show you how to service the iris mechanism, the one on mine didn’t need to be cleaned. It’s a complicated mechanism, don’t open it up just for fun.

Carefully open the rear optical assembly.

Remove the rear element and its housing by unscrewing it. If it’s stuck, use a bit of acetone to soften the seal.

Extract this element with a lens sucker.

Do this to the other half of the rear optical assembly.

This is too-deep to access safely with a lens spanner, use a pipe-key to get it off. Read my article on fabricating a pipe-key alternative.

Use a lens spanner to remove the retainer ring.

Carefully extract this optical group. It’s composed of several elements that’s cemented into a single units so be careful while you handle it.

Here’s another one.

Unscrew the retainer ring so you could remove the front element. Use a bit of alcohol to soften the threads, this ring is usually sealed with paint.

Remove the 2nd group and be careful not to drop it. It’s a cemented group, I will warn you about flooding this with solvents, it could ruin the cement.

Carefully clean each element, if your lens has fungus, read my article about cleaning lens fungus. Do not use the solution at its full-strength, dissolve the solution with distilled water and don’t soak it for too-long or the coating will get damaged.


It took me a few nights to service this since it has plenty of parts. I had a lot of fun but I would rather not go through this again. I hate servicing zooms, it takes a lot of time dismantling the barrel and it takes even more time just to put things back.

The felt lining was replaced with new material. It’s difficult to find the right replacement but you could get some at a milliner’s shop.

It’s now time to adjust the focus. It’s more complicated to do this since zoom lenses require that you adjust the rear and front-focus. The rear-focus could be adjusted at the base of the barrel if you slide the sleeve up. Adjusting the front-focus is a lot easier but going back-and-forth as you adjust either end is the frustrating part. Read my article on how to adjust a lens’ focus, it will show you how to do it in a DIY setting.

Thanks for following my work. If you enjoyed this article, share it with your friends. This site earns $0.30 a day from views alone so each view counts. It is also thanks to the supporters that this site has survived this long. You are helping me offset the cost of maintenance and hosting. See you again in the next article, Ric.

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1 Comment (+add yours?)

  1. Trackback: Repair: AF Zoom-Nikkor 75-300mm f/4.5-5.6 | Richard Haw's Classic Nikon Repair and Review

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