Focusing The Nokton 50/1.5 Down To 0.7m

The new solution of removing the internal stop allows the lens to be used full-range, 0.7m to infinity. This is also true of my modified J-3, done much the same way- internal stop removed, threads files down.

The "mini-Extension-Tube" shim allows the lens to be used 0.7m to ~ 3m. Remove the shim for 0.9m to infinity. No change to the lens is required. That trick will work on a lot of LTM lenses.
 
JSU said:
Lynn--

Wow, now you really have my attention. A serious bravo is in order here.

Please keep the forum updated on your efforts with the CV 50/1.5. And if you get those tools, absolutely let us know.

Should I consider posting my own lens to you now?

--JSU
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Thanks!

I have reached my goal with the Nokton 50/1.5, I have a fast 50mm lens that can focus continuously from infinity to 0.7m, no rings, no shims, opertates just like the Summilux 50 ASPH.

As for sending me your lens... I would make that a cautious... yes.



pevelg said:
Oh my goodness. That would make my favorite lens (ZM Sonnar 50/f1.5) so much more incredible. I wonder what would happen to the focus shift.

With your modification to the Nokton, you can still focus to infinity, correct?

How about with the shims? My understanding is that you cannot, but that DOF would cover the error.
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Have no idea how the ZM Sonnar will perform closer than 0.9m. I suppose that it is one of those try it and see.

Yes, the Nokton can now focus from infinity to 0.7m. You will not be able to use shims on the ZM Sonnar as it is not an LTM lens.

Brian Sweeney said:
The new solution of removing the internal stop allows the lens to be used full-range, 0.7m to infinity. This is also true of my modified J-3, done much the same way- internal stop removed, threads files down.
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Brian,

The modification of the Nokton 50/1.5 is more about moving the stops than removing them. The original infinity stop is not altered and the lens will not focus past 0.7m.

I am sure that there will be plenty of Nokton 50/1.5 owners who want to know if I will do this modification to their lens. I will consider it on a case by case basis, I am not a professional lens repairer nor the 'Mad Gearhead Scientist'.

The modification takes about 3 hours from start to finish, with some custom tools and practice, that time should be about halved. It does require the focusing helical to be disassembled, so it can become a tedious reassembly. I do not have a convenient method of ensuring that the lens is calibrated for correct focus except by using my M5. I will try to get a more standardised method of be able to collimate the lens after modification. Send me a PM if you want to discuss your lens further.

I will be starting a new thread over in the Voigtländer Bessa forum to exhibit photographs taken with the 0.7m Nokton 50/1.5.

Thanks!
 
I know a lot of people want you to document that next lens that you do.

As for "Mad gearhead Scientist"- if the laugh comes involuntarily as you focus to 0.7m, you are most definitely a "Mad Scientist".
 
The question I have to ask is if the manufacturer of the lens restricts the minimum focusing distance to one meter with a design that can be altered relatively easily to get it to .7 mtr ... what was their purpose in doing so in the first instance?
 
Brian,

Not sure about the involuntary laugh, but when you consider that this modification requires putting a big file into a small lens and then filing like a madman... I have to be abit deranged.

I am worried about documentation as there is a huge amount that can go wrong and I do not want to be held responsible for the write-off of someone's Nokton. I will take photos of the next one I modify though with all the disclaimers.
 
I think the 50/1.5 and 35/1.7 were made for the Bessa R, Keith, and limited because of the camera, not the optics.

Roland.
 
Keith said:
The question I have to ask is if the manufacturer of the lens restricts the minimum focusing distance to one meter with a design that can be altered relatively easily to get it to .7 mtr ... what was their purpose in doing so in the first instance?
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Keith,

I have asked this question myself, because it seems that Cosina could have used this as marketing point. I think there are 2 reasons...

1. The Nokton 50/1.5 was released very early in the production of the Bessa bodies and Voigtländer lenses in 1999. The rangefinders of the the Bessa T, R, and R2 only coupled to 0.9m. So there was no in-house incentive to make the Nokton focus closer.

2. The Nokton 50/1.5 is an LTM lens, so that meant that the mount of the lens would have to be modified to allow coupling down to 0.7m.

Now oddly, when the Color-Skopar 50/2.5 was released in 2002, it had a modified LTM mount and the lens does focus to 0.75m

So go figure...
 
There should be a Nobel price for lens hacking, and I know a few here that should receive it 🙂😎

Now, Lynn, would you do yourself a favor and post a detailed DIY manual?

Unless you do want to see your mailbox full of Noktons from all over the world waiting for your magic 😉

Thanks guys, great job!
 
Roundtable at Cosina headquarters:

"They found out! They found out! I told you some genius would find out eventually! Next thing they will find out how to open up the Color Skopars to f1.2, and then what?"

;-)
 
P. Lynn Miller said:
I do not have a convenient method of ensuring that the lens is calibrated for correct focus except by using my M5. I will try to get a more standardised method of be able to collimate the lens after modification.
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Just tape a small piece of ground glass on the film plane of your M6. I use a similar trick when checking the accuracy of my lenses. I think this is what repairpeople do as well.
 
I wonder - since there is more involved in making Nokton focus closer than Nikkor 5cm/1.4 - how sure are you that lens (Nokton) still focuses correctly at ALL focus distances? Could you also give a more detailed explanation as to what you did to make it focus closer? Cause if it works as you say it does - you just put Cosina to SHAME! Great work - regardless, though. Hope to see more samples from your "fixed" Nokton.
 
The Nokton should be just fine across the full focus range, the RF Cam moves 1:1 with the optics, and the RF of the camera is calibrated to 0.7m. Same with the Nikkor, filing down the threads is required to allow the RF follower to not get blocked as the cam moves inside the mount of the lens.

NOW- the Jupiter-3 and Jupiter-8 modified for close focus does have the problem of focus not being accurate across the entire range. But, that is for a different thread.
 
Krosya said:
I wonder - since there is more involved in making Nokton focus closer than Nikkor 5cm/1.4 - how sure are you that lens (Nokton) still focuses correctly at ALL focus distances? Could you also give a more detailed explanation as to what you did to make it focus closer? Cause if it works as you say it does - you just put Cosina to SHAME! Great work - regardless, though. Hope to see more samples from your "fixed" Nokton.
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My modified Nokton focuses correctly at all distances, right down to 0.7m. The reason being that I actually re-machined(by hand) the close-focus stop. This modification only allows that lens to be extended further along the focus helical by 0.9mm. The tricky part of this modification is the machining involved. Cosina could have done the 'mod' on the lens in less than 1 sec with their CNC mills while manufacturing the lens. But modifying the lens after the fact is more tedious and complicated.

If you are a willing to disassemble your Nokton 50/1.5, you will find that the focus stop is milled into the main lens housing. So the lens has to be disassembled entirely, leaving only the main housing, which then has to be reworked so the close focus stop is moved further along. Care has to be take not touch the bearing surfaces of the focusing ring and helicals on the housing. Nick those with the file and you will have a rough focusing lens forever, not to mention possible wobble.

The modification makes no changes to helical pitch, infinity stop, focusing cam shims, or infinity focus indexing. So the lens is unaffected except that is now focuses to 0.7m instead of 0.9m.

I could say shame on Cosina as well... but I do not want to sound ungrateful for the huge contribution they have made to the rangefinder community. Without Cosina we would be much poorer in RF lens variety and choice, and I never want to take their efforts and work for granted. I just wish that Cosina would stop operating in the shadow of Leica and show us the world-class optics producer that they are. Time for Cosina to set its own rules of play.

Thanks, Brian... I do not know much about the J-3 or J-8.
 
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That's what I content myself with doing Fred. Or using a tele instead of a 50.

Still from 1m to 0.7m corresponds to a crop factor of 1.4, or half the film real estate.

Roland.
 
I wonder if there is any progress on this - I mean - did you have a chance to do any more lenses and take pics of this procedure? I am very tempted to get Nokton and try this modification on it - so I wish I have a bit more info/pics for that.
 
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