Nikkor-N 5cm/f1.1 LTM Lens Needs Help

[GMOG]

I have on the bench a Nikkor-N 5cm/f1.1 lens in LTM.




The lens came to me with a loose aperture blade.






It looked like this was going to be an easy fix, until I tried to remove the black notched ring that holds the aperture mechanism in place. I am unable to turn the notched ring out more than a few degrees, and closer inspection reveals that the ring was cross-threaded by the last person who worked on this lens. The ring is not sitting level with the rest of the lens, and there is a visibly larger gap between the ring and the barrel on the 9 o'clock side (above photo) where the ring is higher, compared to the opposite side. I believe that the loose blade's pin came out of its slot because the slotted actuating ring is allowed to move up and down more on that side.

What can be done about this? I've thought about tapping on the black notched ring, where it's high, to see if I can get it to pop back down into the threads, but I hesitate because I do not want to make things worse. I'm not sure what else can be done given the tools I have access too. The black notched ring binds up tight, so tight that I fear causing some serious damage if the spanner were to come out of the notches while under pressure. I've tried gently maneuvering the blade back into place without luck. This thing needs to come apart in order to reposition the loose blade. What to do!?!

I'm looking for ideas on how to handle this. Maybe sending it out to someone with more experience would be best, but who might that be? The lens is in great shape overall. It seems well worth the time and possible expense.

Thanks for looking!

 

[raid]

Call DAG. Ask him if he fixes it.

 

[lukx]

Wow that is a cool and rare lens and it looks absolutely pristine. I am an amateur lens repairman myself, but in your case I'd be very hesitant to proceed. Heat might help, but I would definitely remove the rear optical block before doing anything else. It's probably best to ask a professional. Not knowing where you are located I cannot suggest a repairperson. Whomever you choose, make sure to clearly state the problem in advance.

 

[Miles.]

I’d send it to either Kiitos Camera in Japan (who probably have the most experience with this lens) or S.K. Grimes in RI.

S.K. made new aperture blades for mine when the original ones were no longer available, and if the lens ends up needing machining he’s the only person in the world I’d let touch it.

best of luck.

 

[Livesteamer]

You might have to cut the ring to enable its removal and then have someone like S.K. Grimes make you a new ring. Take your time and think a lot about this and I wish you Good Luck. Keep us posted how it works out. Joe

 

[jonmanjiro]

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You should not need to unscrew that piece. I've never seen a Nikon RF lens with an aperture mechanism front piece that unscrews like you're trying to do. In every Nikon RF lens I've disassembled, that piece slides in to sit on top of the aperture blades and is held in place by a recessed circlip just above it. That piece is also linked to the external aperture ring via a screw (otherwise how else could you change the aperture setting). You need to remove both the circlip and screw to take that piece out and access the aperture blades.

If you could post a photo taken on more of an angle, we could probably see where the circlip goes.

It should be an easy lens to work on IF YOU KNOW WHAT YOU'RE DOING. If you don't know what you're doing, you're just going to mess up a very rare and expensive lens, so send it to someone who knows what they're doing.

FYI KIITOS in Japan makes replacement aperture blades for this lens, but they do not sell them separately. They will only sell you them if you send your lens to them to be repaired.

 

[raid]

Once I had a Zeiss Planar 85/1.4 that seemed to have broken aperture blades. Only Don Goldberg was knowledgeable on such issues when I tried out several repair people. He told me that for me he could rebuild the blades, but he usually does not offer such a service. It seems that KITOS is an option.

 

[GMOG]

You should not need to unscrew that piece. I've never seen a Nikon RF lens with an aperture mechanism front piece that unscrews like you're trying to do. In every Nikon RF lens I've disassembled, that piece slides in to sit on top of the aperture blades and is held in place by a recessed circlip just above it. That piece is also linked to the external aperture ring via a screw (otherwise how else could you change the aperture setting). You need to remove both the circlip and screw to take that piece out and access the aperture blades.

If you could post a photo taken on more of an angle, we could probably see where the circlip goes.

It should be an easy lens to work on IF YOU KNOW WHAT YOU'RE DOING. If you don't know what you're doing, you're just going to mess up a very rare and expensive lens, so send it to someone who knows what they're doing.

FYI KIITOS in Japan makes replacement aperture blades for this lens, but they do not sell them separately. They will only sell you them if you send your lens to them to be repaired.

I appreciate your reply. I agree, being unfamiliar with the lens makes me especially cautious about going any further, and I have decided to stop and let someone else deal with it. This lens doesn't belong to me, so I am even more careful when thinking of how to proceed. In my own business (Swiss-trained watchmaker with almost 30 years at the bench) I have learned to accept my limitations and have no problem letting other service providers do things for me that are beyond my knowledge and skill/tool set. I will NOT mess up this lens any more than it already is, and I want it known that I am not the person who left scratched surfaces and damaged notches! 🙂


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Here's the shot you requested, taken from an angle. There's no circlip in there that I can see, at least not on this side. You can see the tip of the screw that links the slotted disc/ring with the aperture ring on the RH side, out of focus, at about 3 o'clock. It appears that the slotted disc/ring that controls the blades is held in place by the cross-threaded black notched ring. It's high on one side, so the slotted control disc/ring moves up and down more on that side, and this, I believe, is what allowed that blade to come loose.

At this point I've put the lens back together, and I'm going to recommend that the owner send it to Kiito, or to Grimes, or to DAG. It's well worth the investment, I believe.

Thanks to everyone who shared their thoughts and experiences. If the owner decides to invest in proper service for this rare and valuable lens I'll be sure to let y'all know how it works out.

Have a great weekend!

 

[raid]

Many years ago such a lens was selling for $5000. What is the current market value of such a lens? Nikon-Kiu once lent me his Nikkor 5cm 1.1 for a lens test of 50mm lenses.

 

[raid]

I just checked online .... its value has dropped one cent 🙂
https://www.ebay.com/itm/11519411686...BoCAKYQAvD_BwE

A ZUNOW gpes for an additional $5000 ! ...
https://www.ebay.com/itm/1339178484...gSWaFNjvOl4r4GUgY9nuf7lUft8bhnKBoC60oQAvD_BwE

 

[James24]

Many years ago such a lens was selling for $5000. What is the current market value of such a lens? Nikon-Kiu once lent me his Nikkor 5cm 1.1 for a lens test of 50mm lenses.

A Leica thread mount version of this lens is worth significantly more than a $5000 Nikon S mount version. Very very few were made.

 

[raid]

I used a Leica mount version. I had no Nikon RF camera then.

 

[GMOG]

The person who owns this lens is under the impression that it's worth somewhere between $10,000 - $20,000 USD. Of course, the value of this particular lens couldn't be that high considering the lack of a functioning aperture. I dug around a little online but all I saw were S mount versions for sale or sold.

I returned it to the owner this morning, and I suggested he spend the money to have it repaired properly by one of the providers mentioned above. It's out of my hands now, and I am quite relieved! Now, back to that old pocket watch that's on the bench . . . .

 

[Livesteamer]

About a month ago a lens just like this one was on e bay, complete with damaged aperture blade. It sold twice, the first time for 11 or 12 thousand dollars and after the buyer did not pay it sold again for $10k if I remember correctly. The head bartenders site has information on this lens design and warns not to open and close the aperture quickly or the blades can be damaged. Good for you helping a friend and I hope it works out for the owner. Joe

 

[James24]

The person who owns this lens is under the impression that it's worth somewhere between $10,000 - $20,000 USD. Of course, the value of this particular lens couldn't be that high considering the lack of a functioning aperture. I dug around a little online but all I saw were S mount versions for sale or sold.
.

I don't think he is far wrong. Another LTM lens with issues sold on eBay for US$9000 ( see https://www.ebay.com/itm/275072827372? ) . The listing itself makes an interesting read.

I recall seeing an immaculate copy for sale some years ago for, I think, $25,000. The stuff of dreams!

 

[James24]

About a month ago a lens just like this one was on e bay, complete with damaged aperture blade. It sold twice, the first time for 11 or 12 thousand dollars and after the buyer did not pay it sold again for $10k if I remember correctly. The head bartenders site has information on this lens design and warns not to open and close the aperture quickly or the blades can be damaged. Good for you helping a friend and I hope it works out for the owner. Joe

Just seen your post after I posted mine. I think we are talking about the same one!

 

[raid]

Consider that some Canon FD lenses are selling for $3000+.

 

[GMOG]

I looked at the completed auction linked to in post #15. The problem with the aperture sounds similar to what I found in the lens I had on my bench. I'm glad I got out when I did. 🙂

 

[GMOG]

This lens is back in action. The owner sent it to S. K. Grimes, who restored it to proper working order, and it didn't cost a lot of money. I want to thank everyone who participated in this discussion.