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Repair: Nikon 75-150mm f/3.5 Series E

Hello, everybody! Such a lovely weekend we have now at Tokyo, unfortunately for me I ate a lot of cheese tarts and we all know that cheese is not a friend for the lactose intolerant. I am also happy that my child is approaching her 1st birthday soon. Time flies so fast, it is as if it was just a few months since she was born and now here she is, bouncing around like a hyper bunny! This post took me several nights to make because I want to make this easy to read so I hope that you enjoy this!

Introduction:

This lens does not need a lot of introduction. The E 75-150mm f/3.5 is considered by many to be a hidden gem of a lens despite being a Series E lens, a line of lenses made by Nikon to complement the entry level class Nikon EM camera. The Series E lenses are made with cost as the main factor while maintaining superb optical design and performance. Many lenses under the Series E label are superb performers and they have acquired such a following in the used lenses market that they sometimes cost more than lenses on the Nikkor series!

IMG_2552(I got this one for very little money for the purpose of writing this. If I can afford the lens, I will get it to accommodate your request. This one is still in pretty good shape.)

Just like any popular and tested lens, this lens is also not exempt from known issues with the zoom creep problem being the most well known. This issue of the zoom creeping (the lens changes length on it’s own due to gravity) seem to plague a lot of photographers who own this lens (mine has a little bit of it). Another issue is that the focusing ring seems to be too light or not damped at all (lubricant choice).

There have been numerous fixes for the zoom creep problem ranging from bandaid fixes to more permanent ones and here they are:

Samples of Temporary Solutions:

  • inserts in between the zoom ring and the barrel
  • heavy grease applied to the zoom guide slot

The Permanent Solution:

  • Replacement or reinforcement of one or both felt linings

This lens is going to be dismantled to it’s bare components so that this guide is also going to be relevant for people who want to fix other problems outside of the zoom creep issue. This lens is pretty straight forward with not a lot of gotchas. I will show you where these surprises are later in the disassembly steps so they will not catch you off-guard.

42_danmen1Nikon went all out for the design of the optics. The optics is a marvel of optical design in that Nikon managed to put in so many things in such a small package while maintaining high performance and features.

I would even argue that this lens could have beaten true-blue Nikkor pro-grade lenses in a lot of scenarios. So I advise people who have not bought this lens get one for fun or for pro work. Just search Google because there is no shortage of praise for this lens’ performance.

There are many rumours surrounding this lens such as this lens being subcontracted to a company named Kiron (a small player) and that the previous version were flimsier when compared to the later ones. Wether these are true or not we shall find out as we go part by part in each step of the disassembly so pay attention to the pictures and then decide it for yourself.

As a good article for supplementary reading, you can check out my post about the amazing Zoom-Nikkor 80-200mm f/4 Ai-S lens. There are similarities with both lenses and if you are familiar with one of them then you can easily take apart the other.

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.

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 (Focusing Barrel 1):

This is a zoom lens and that means that this lens cannot be clearly taken apart in 2 major subassemblies like you usual vintage Nikkor prime (focusing unit and objective). The steps can get confusing as I go back and forth so please bar with me. I will try my best to explain which step should be relevant for certain problems but I advise that you also exercise your own judgement.

For folks who need to fix the annoying zoom creep problem, start by removing the front focusing barrel. This is also a nice starting point for general overhaul but opening the lens from the rear might be a better option.

I always work while the lens is focused all the way to infinity. This serves as a good point of reference I will come back to this at every step.

IMG_2553Begin by removing this rubber sleeve. Be really careful with it because a small puncture or rip can cause this to tear, rendering this part damaged and undesirable, most specially for collectors who value the aesthetics over the functionality of a lens.

I removed the rubber sleeve by running a thin rounded wire/rod under the sleeve to loosen the rubber cement that they used as adhesive. Carefully go about the whole circumference of the sleeve until it is loose enough for you to pull. Pull slowly and gently as the rubber is old and WILL rip under a lot of stress.

While you are at it, you can also remove that thin brass strip covering the canal for the tiny screw and washer that serves as a guide for zooming. This is usually secured by scotch tape and mine was so brittle (due to the age) that the tape literally disintegrated!

IMG_2555Next, remove the screws that secure the ring with the moulded numbers. Under this ring is the inner focusing barrel. This ring and that barrel is just one piece so I will use the term interchangeably. Here is one of the 3 screws (circled).

IMG_2556And here’s another…

IMG_2557And finally, the last one!

IMG_2558The inner focusing barrel should slide off easily. Before doing this, be sure to mark/scribe the position of the infinity symbol in relation to the focusing barrel as a guide for later use.

IMG_2559Now, simply remove this screw and washer and keep them in a safe place. This washer has no replacement and can be troublesome to fabricate. It is also important to  mention that this screw should never be tightened, but simply left loose (but secure). Over-tightening it will cause it to squeak when you zoom in and out even if you apply a spoon full of grease.

Disassembly (Helicoid):

You can skip anything related to the helicoids if you only need to fix the zoom creep thing but since these are accessible, I highly advise that you service the helicoids as well because doing so will give the lens several more years or even decades before you need to change the grease again. This will also fix another known issue with this lens, undamped focusing.

IMG_2567You can simply unscrew the helicoid at this point. Please be careful because this part will separate in just a few turns. The front barrel is connected to the outer helicoid so it goes off as well.

IMG_2568As with your regular double helicoids, you should also mark where this thing separates. It is also worth noting that in my sample, the number “3” at the start of the serial number in focusing barrel coincides with where the infinity mark should be. This was convenient for me when I was reassembling my lens. I don’t know if this is also the case for other lenses so do not take this as a universal truth.

IMG_2569The helicoid looks dry as if grease was never even applied to this part. That explains why this thing was not even damped as you turn the focusing ring, there was no resistance at all. This may be what some people want but I like my focusing to be damped even if I want my lenses to be feather-lite when I turn the focusing ring.

Now that the front barrel is gone, the focusing barrel comes off easily. You can now access the inner parts so that you can fully disassemble your lens.

Disassembly (Focusing Barrel 2):

Now back to the focusing barrel. This step can be a long and confusing step so please bear with me. The inner focusing barrel can be a pain to dismantle and access so if you are not comfortable with it after reading this article, you can simply omit servicing it and work on the outer focusing barrel alone since you can fix the zoom creep problem by just working on the felt lining found on the outer zoom ring.

IMG_2570Under the focusing barrel, you can find this thin felt strip. Mine was about 3mm think and looks OK so my lens does not have any severe zoom creep going on. If your’s have it then this is the part that you should replace or re-pad. A simple lining made from a thin strip of brass is more than enough to raise this felt strip so that it grips the barrel more. Replacing this part with something else is also an option if you found that yours is in a bad state and only a replacement is viable. A strip or rubber laminated with felt paper should be perfect.

Also note that this is only one of two parts where you can fix the zoom creep problem. The other one can be found in another barrel and can be a pain to remove. If fixing this lining helps then you probably do not need to go too far unless you really want to do a perfect job.

IMG_2571Now, to remove the inner helicoid from the main barrel, simply remove the 3 screws that are used to secure it. You should also note where that small indent (encircled) should align with the rest of the lens so that you get to align your lens perfectly as you reassemble it. Align it with a stationary part such as the chrome grip or anything that does not rotate so that the position is constant as you go about rebuilding your lens. Another way is to mark the position of this indent on the surface underneath it (on the main barrel).

IMG_2574When you remove the helicoid, be sure that you do not lose or damage the thin brass shim under it. It was used as a washer or gasket of some sort. These brass shims are usually used for focus calibration but I do not think that this is the case for this lens as it was found in a place that is not accessible or convenient at all for calibration.

Focus calibration on this lens can be done on the front barrel and I will show you how and where to do it in later steps.

IMG_2575You can remove this glass element and it’s case by using a lens spanner. These 2 encircled holes should give you a clue.

IMG_2576And off it goes! Be careful not to drop it to the floor.

IMG_2577Removing these 2 screws will free the stop under it. It is not necessary to remove the stop but I did not know what to expect when I was disassembling this.

You can also see 1 of the 3 zoom rollers™ in the picture (I invent names as I go!). This part can get confusing so read the next step carefully.

IMG_2578You should remove these 3 rollers in order to separate the inner focusing barrel from the main barrel. If you look at the picture above, one of the rollers is shorter than the other 2. The reason why one is shorter is because the shorter one slides under the stop and the 2 longer ones serve as bumpers for the stop. Now that you know what these things do, you can come into the natural conclusion that the shorter one should lie in between the 2 long ones or else the focusing ring will not turn properly because the stop is being obstructed.

As an easy guide to where these should be positioned, just think that the long ones should be screwed at both ends of the focusing range, one at infinity and another at the minimum focusing distance (1m). Of course, the short one should be in between these 2.

Be aware that these 3 rollers secure a floating element holder and removing these 3 frees that part and there is a potential that it may damage another glass element under it is high so please check the next steps to see what I mean so that I can help prevent an expensive mistake from happening!

IMG_2580Now that the 3 focusing rollers are gone, you can now separate the inner focusing barrel. The line in the picture just show where each roller travels when you zoom the lens. This should give you an idea as to how much grease you should put into this thing (not a lot).

Also seen in the picture is another roller that belongs to another set of rollers that is used for focusing, I shall call it the focusing rollers™! These rollers are used to keep the middle floating element in proper alignment as you focus in and out.

IMG_2583The three zoom rollers™ that you just removed are all connected to this part. This part is used to hold the floating glass element that we just removed a few steps before. This thing will move in or out as you zoom the lens.

IMG_2581Same thing with the outer focusing barrel, the inner focusing barrel has a felt lining under it as well. If you are only interested in fixing the zoom creep then you can simply replace or fix this and ignore the rest of this post and just read it for educational purposes.

Disassembly (Rear Parts):

This step is not essential for people who simply need to fix the zoom creep so you can skip this part unless you need to do a complete overhaul or some fungus cleaning. My aperture assembly (iris) did not need to be serviced so I did not bother to open it up.

IMG_2561Remove these 4 screws to release the bayonet mount. Be careful not to scratch the glass!

IMG_2562The aperture ring and the bayonet should come off easily BUT be careful and go slowly! See the next step to know why.

IMG_2597The aperture ring also houses the mechanism for the detent and clicking when you turn it. I was lucky that Nikon used a heavy grease (something like lard) on this very part so mine did not jettison across the room! Nikon sure went cheap on this part because the aperture ring is made of plastic and the detent mechanism is kind of rudimentary.

The spring should go into the hole and the small bead/ball bearing should sit on top of it. It can be a challenge to put back together as you will see for yourself later.

IMG_2563To remove the rear optical block simply remove the 3 screws securing it to the main barrel. But before doing so, remember to mark the alignment by scribing a mark on the surface of the main barrel and the rear optical block. This is a precise alignment so be careful. I just scribed a single line and that is enough to for me to know how things should align later.

Nikon used plastic on this part of the rear optical block. While this is fine and adequate, it shows where and how Nikon cut corners in order to make this lens cheaper.

IMG_2565The rear optical block should come off easily. Also be careful not to drop the whole thing to the floor! The rear elements can be accessed by unscrewing the retention ring. This ring is generously glued so please use some acetone to soften up the glue before you proceed.

IMG_2566Also be careful when handling the rear optical block because at this point, the exposed iris assembly can easily be damaged. Just check this thing out, the metal plate that secures the rotator plate and aperture blades inside is just made of stamped metal. On a Nikkor, this part is usually milled from a single piece of alloy.

IMG_2582Remove the chrome grip by removing the 3 screws that holds it in place and you should be able to easy slide it off. The circle shows one of the 3 screw holes.

Disassembly(Other Stuff):

I did not know where to categorise these parts so I consolidated them all together here for convenience. For people who are only interested in the zoom creep problem, you can skip this part because these have nothing to do with that problem at all.

IMG_2584To remove this protective metal sleeve, simple remove the 3 screws that secure it.

IMG_2585It simply slides off without any problems. These things aren’t usually glued to the main barrel if there are screws securing it otherwise Nikon will glue these things and it can be annoying to get these things off if they did glue them down. Copious amounts of solvent must be used.

This sleeve is actually more cosmetic then protective and you can just leave it there but if you want to clean your lens thoroughly then removing this part is a must because this part usually collects dirt and grime underneath it.

IMG_2587Now, remove these 3 focusing rollers™ rollers so that you can proceed. Unlike rollers from before, these 3 rollers all come in the same length so don’t worry about where and which way they should go.

Before proceeding, please look at the next step so you will be aware of what happens when you remove these 3.

IMG_2589The 3 rollers hold this floating element in place. Exercise caution to prevent an expensive accident from happening by making sure that this thing does not drop to the floor.

IMG_2590This guide barrel simply slides off now that all of the rollers are gone. This barrel mainly serves as a guide for all of the 6 rollers. You can now see and appreciate the main barrel of this lens now that nothing is obstructing it. The main barrel is milled from a single piece of alloy and looks expensive to manufacture.  Nikon went cheap on most of the lens but they sure spent money on the most important structural part of this lens!

Disassembly (Front Elements and Focus Calibration):

Again, this step has nothing to do with the zoom creep problem. For the folks who simply need to clean the front elements or calibrate the infinity focusing of this lens, this is it.

IMG_2591Loosen up this set screw to remove the front elements assembly. Be careful not to damage this screw because this part is non-standard and can be expensive to source.

IMG_2592Simply unscrew the front elements assembly off. Be careful not to damage the screw hole! The front elements assembly can be opened up by using a lens spanner. I also used a lens sucker to safely remove the front element.

You may also want to be careful with the acetone since the front elements were cemented together with Canada balsam and you do not want that part to get damaged accidentally by  contaminating them with acetone or solvent.

As you can from picture above, there are brass shims under the front elements assembly. These brass shims are there for adjusting the infinity focus of your lens.

How to adjust infinity focus:

I would also like to mention that this is the part that you should adjust if your need to fix your infinity focusing. If your lens focuses past or short of the infinity mark if you focus on a distant object (or some clouds) then all you need to do is loosen the tiny set screw on the previous step and then turn the front elements assembly until your focus lands exactly on the infinity mark and then tighten the set screw again so that the front elements assembly stays put.

It is also worth noting that this lens exhibited some focus shift as I zoom in and out while focused to infinity. All this basically means is that when the lens is focused all the way to infinity and focused on a distant object like a building kilometres away from where I was, the focus dot is solid at 150mm but when I zoom to 75mm, the dot flickers. I calibrated it to focus perfectly to infinity at 75mm and then the problem presents itself on the other end of the lens this time. Having this in mind, you should which end of this lens (75 vs 150mm) is more important to you at infinity. This is not a big deal since a flickering dot still meant that the lens is still in focus somewhat, for me that is “close enough”.

Post Mortem:

I would put this lens on the easy side if you are an experienced repairman of older Nikkors. I was expecting that this thing would take me 2 nights to overhaul mechanically but I only spent close to 3 hours fixing this.

IMG_2595As mentioned in the commentary, one of the 2 longer rollers should fit into the screw hole that corresponds to the infinity mark. The other one should be installed on the 1m mark. The shortest one should be placed in between the 2 long ones.

This part (the 6 rollers) is the only confusing part of the whole lens assembly/disassembly process so please take your time documenting each step and refer to this blog if you miss anything just in case. It is not frustratingly difficult but it might take longer than it should so don’t give up!

IMG_2598As you can see from the picture above, the lens now looks clean because I took the time to clean everything that I can including that broad rubber grip. The rubber grip was cleaned with a clean toothbrush. You can also scrub this with dishwashing liquid if yours is really dirty but be sure to use unscented ones or you will leave oily residues on the rubber due to the oils used for the fragrance and moisturisers.

As usual, I soaked all of the metal and hard plastic parts in an alcohol bath so that any dirt or grime will be softened enough for me to wipe off using a clean lens tissue or Kleenex. I do this because simply wiping the surfaces off with a solvent and tissue is not enough to clean grime that has deposited and hardened over the decades. Wiping alone will also not be enough to reach stubborn dirt on the corners and crevices. I usually soak these for a few hours to overnight depending on my mood.

Conclusion:

I did not go about thoroughly cleaning the lens elements because I thought that all of the dusts that I saw were only concentrated on the front and rear elements assembly alone. I was really stupid for thinking that this was the case because looking through lens while it was facing the ceiling lamp revealed that the lens was still dusty inside! While the majority of the dirt was gone because I wiped the front and back elements clean as well as opening up the front lens assembly to blow away any dirt that I saw, majority of the junk that I am seeing now seems to be deposited deeper into the objective! This was such a waste of effort and it was certainly a lesson learned. Just like what I learned from a German room mate of mine before – If you do something, be sure to do it right. Laziness has no excuse!

Most of the people who asked me to do a tear down of this lens only needed to fix the zoom creep of this lens so I would advise them to also re-grease the helicoid while they are at it. I used a stiffer grease on my lens (S30) because I wanted more damp. While the front and middle elements are exposed and accessible, it is also a nice idea to get a blower to clean any dust that have settled on the surface of the lens.

I hope that you have enjoyed this blog post as this one took me some time to make. I also would like to apologise for the ordering of the steps. This can be confusing for people who simply wanted to fix the well known zoom creep problem of this lens. I wanted to take my lens apart because I wanted to see what is inside of it since I am passionate at learning and sharing what I found.

Thank you very much and as always, if you have enjoyed this article it would help me a lot if you share or re-post this on the net. I also intend to start an e-commerce shop here in the blog and if you need something, please feel free to write me a request! Until next time, please stay healthy and may you find a great deal in your junk hunting! Love, 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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17 Comments (+add yours?)

  1. Aleksi Lausti (@Lausti)
    Oct 02, 2016 @ 17:31:15

    Thanks for the great article and hard work that went into it. Did you find any evidence to support the rumour that this lens would have been made by Kiron? Personally I think it is mainly a myth as it has been perpetuated mainly by one or two pseudonyms of various forums now for years but without any evidence to back it up. Out of curiosity I would love to hear your take on this issue after disassembling the lens. Not that it matters in the end who made it as it is a great lens nevertheless!

    Reply

    • richardhaw
      Oct 03, 2016 @ 09:19:01

      Hello, Aleksi!

      Glad that you liked the blog. having opened this lens, I did not find a lot of differences in it’s engineering to point that this lens came from another maker. It might be, there is a possibility but until Nikon says anything, it is only speculations. I can try to find anything on the Japanese internet and see if something can shed some light into this.

      It is a great lens! Unfortunately, I am not a zoom lover as I prefer primes for a multitude of reasons.

      Ric.

      Reply

  2. Trackback: 36~72mm f/3.5 Nikon Lens Series E Disassembly and Cleaning – My Take on Photography and Diving (Underwater Photography Mostly)
  3. Trackback: Internet Nikon Repair Resources – My Take on Photography and Diving (Underwater Photography Mostly)
  4. Oleg
    Dec 21, 2016 @ 23:33:08

    Richard, thank you very much for the great article!

    I read it because I recently bought a Vivitar 70-150mm F/3.8 (with Canon FD mount) like the one shown here http://www.ebay.com/itm/Canon-FD-Fit-Vivitar-70-150mm-F-3-8-Manual-Focus-Zoom-Lens-Ex-/361836555337?hash=item543f23ac49:g:ruYAAOSwiONYNZ6B

    Unfortunately it turned out that focusing doesn’t work on my lens at all. The push-pull zoom works. The focusing ring turns easily (though it goes about 1cm beyond of infinity mark), but no focusing happens. It seems that none of the optical elements are moving inside of the lens when I turn the focusing ring.

    Can you please give me some hints about what do I need to check first in order to get the focusing working? How far may I need to go in disassembling of the lens to make it work?
    I don’t have any experience with lens repair, so as a beginner I would prefer to not touch things which are not necessary for the repair 🙂

    I have googled my lens on web and in youtube and unfortunately didn’t find any repair-related articles or videos. So I even don’t know how many groups does the lens have and which of groups should move during focusing, but I think its design might be similar to Nikon 75-150mm f/3.5 Series E.

    Thank you in advance!

    Reply

    • richardhaw
      Dec 21, 2016 @ 23:51:34

      Hello, Oleg!
      I am not sure about the Vivitar but the construction should be similar to the Nikkor. If you can remove the rubber grip from the Vivitar, you should see a small square copper washer. It is very delicate and small so it might have gone loose. There are a few things that can happen to make your lens like that. Another one is the front part, maybe some screws came off. Ric.

      Reply

      • Oleg
        Dec 22, 2016 @ 21:50:48

        Thank you, Ric, for your answer!

        I have “primed” the rubber grip and it looks possible to remove it, so I will check what is underneath.

        The lens has also a bent filter ring. So the lens might have been dropped and it could somehow affect the focusing function. First I need to fix the filter ring, because it’s currently impossible to take name ring off the lens.

        Thank you again, and merry Christmas to you and to your family! 🙂

      • richardhaw
        Dec 23, 2016 @ 00:26:39

        Hi, Oleg!
        there is a way to fix that. One is to buy a filter vise and another is to just hit it with something like a wooden stick. Ric.

  5. Tony Sanchez
    Apr 01, 2017 @ 23:16:12

    Hello! My screw in your 7th picture (the one that fits in the tiny washer) seems too short. Do you know what size that screw is? I would like to get a replacement, but don’t know the size.

    Thanks,
    Tony

    Reply

    • richardhaw
      Apr 02, 2017 @ 01:24:46

      Hello, Tony!

      You mean the screw that holds the nut in place for the thrust action rail? The nut is hexagonal is it? Is it too short that it cannot reach into the nut? That is unusual and it might have been tampered with or you might have jumbled up the screws.

      https://richardhaw.com/2015/12/29/best-practices-part-1/

      I forgot how big they were but I discussed the standard sizes for Nikon screws in the article above. If I am correct, it may be the standard M1.4 screw and at the biggest, the M1.7, be careful with the correct pitch by the way.

      Reply

      • Tony Sanchez
        Apr 03, 2017 @ 01:13:22

        Hello! Yes, that’s the screw. I got the lens used and the focus ring had significant side to side play. When I removed the rubber and thin metal strip, I found that the screw wasn’t screwing into the hole. I’m thinking the previous owner banged the focus ring against its limit, thereby loosening the thread (essentially it may be stripped). I was thinking of getting the next sized screw and tapping it in. Any other ideas to remedy it?

        Thanks,
        Tony

      • richardhaw
        Apr 03, 2017 @ 01:58:04

        Hello, Tony.
        Wow, that sucks! If that is the case, you will have to see if the thread is still OK. You can test it by trying to screw-in a good screw of the appropriate size (M1.4/M1.7) and if it screwed in neatly then the thread is still OK. Otherwise, you will have to re-tap it just like what you said but be careful while doing so. It might be better to fabricate a new nut by filing a similar nut into the correct width. That was a damn hack job you got there. I ruined my helicoid stop once and my hack job wasn’t that sloppy. Ric.

  6. PeterB
    Apr 27, 2017 @ 03:59:57

    Richard,
    I found your blog post the evening I decided to take apart my 75-150mm Series E. Zoom creep isn’t the main reason, as I could easily live with that, but a random tendency to produce partially out of focus images, especially at the longer focal lengths. I have not been able to determine what exactly causes it, but I am guessing there is enough lateral movement in the lens due to worn out felt that allows the front element to shift enough to get out of alignment. I don’t really know the mechanics of all that very well, even after studying your images. Also, the out of focus area is usually only the left third of the image. Nothing dramatic but clearly visible even at lower resolution than the original – e.g. here – compare trees top left with center https://flic.kr/p/Jo5Xqs

    detail crops at full sensor resolution left side
    https://www.flickr.com/gp/speedcenter/3945Ew

    image center
    https://www.flickr.com/gp/speedcenter/01K0od

    Where would you suspect the lens to be failing when images only from time to time are out of focus on the left side? The examples I have are all at infinity. I could do some controlled tests at shorter focal distances to see if I can induce the problem just by holding the lens barrel in different ways, but perhaps this is something you can already diagnose based on what I told you here.Obviously, I’d love to hear that this is just a loose lens barrel symptom.

    Reply

    • richardhaw
      Apr 27, 2017 @ 04:06:15

      Hello, Peter!
      an unevenly focused image is an indication of only 1 thing! One of more elements in your lens is misaligned, has the lens been dropped or serviced by somebody prior? Ric

      Reply

  7. PeterB
    Apr 27, 2017 @ 16:50:40

    Richard,

    I have no idea what the service history of this lens is, so I can’t say it was dropped or opened up before. I figure there’s nothing to lose at this point and it’s not like I am going to pop open my 600mm f/4 as my first lens repair attempt.

    The one thing that’s not clear to me with the misaligned glass is the lack of problems on some frames. The only explanation is that there is some movement in the barrel and it aligns ok at times and then it doesn’t.

    Recently I bought (and returned) a used Rokinon 24mm f/1.4 – it was so horribly decentered that it was completely useless. Focal plane went diagonal into the distance. However, that lens was bad, any aperture, any focal length. Very different with this lens.

    The below image was taken minutes after the other shot with the problems I linked to above. Here the left side is fine
    Wizard Island crater inside of crater lake

    When it works, this little lens is incredibly sharp for it’s size and cost. Perfect for me to haul in a backpack to places I cannot bring the “good stuff” that’s either too valuable or heavy or both.

    This variability and lack of noise that would indicate loose element suggests to me that it may be related to the moving parts of the lens, not something that has been knocked out of alignment permanently.

    Anyway, I’ll probably take it apart, just as a learning experience, following your great instructions. I am not going to use it in its current state any longer.

    Reply

    • richardhaw
      Apr 28, 2017 @ 06:43:08

      Hello, Peter!
      Now, if the lens wobbles then there is a big chance that the elements are thrown off-axis and this is what is causing the uneven sharpness. I will admit that I am very forgiving when it comes to this and I do not even think about this at all due to the nature of what I usually shoot. Ric.

      Reply

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