Nokton 50/1.5 Close focus modification - instructions and photos

[Krosya]

As it is Nokton focuses down only to 0.9m. To some (me) its a serious drawback. Thanks to P.Lynn Miller, who was brave enough to try this first and gave me courage to try this myself. This is a difficult modification, so I would think hard before doing it. (however it would be VERY SIMPLE for a Cosina Factory, as you will see). At the end - it's all worth it for me.

Here is what lens looks like at the minumum focus BEFORE the modification:

 

[Krosya]

What you will need:

 

[Krosya]

I'm not sure if this can be done without taking the front section of the lens off - I think it may be possible, but it made it easier for me to handle things, so I did.
So:
1.Take off the front name ring - it just unscrews with some tension tool.
You will see 3 black phillips screws and one silver flat one. :

2. Unscrew all black ones and remove a black housing ring (part of barrel), there will be silver rings(shims) under it, with 6 holes on them, remove front optical group - it just lifts up and finally lift apperture ring - be careful - there will be a small ball inside - for apperture clicks. Dont lose it. There is a spot for it on the side of the apperture housing - when you re-assemble the lens.

3. Turn the lens over and unscrew the mount - 3 silver screws, make sure to mark the position of the screws, so when assembled lens orientation is correct on camera.

4. After mount is off - here is what you will see:

Note the marked areas - before any further steps, you want to mark/note all thes positions - VERY PRECISELY or your lens will not focus correct. Note 3 black screws that are circled. Also, there is an opening - marked with red bracket on photo - you want them to return to the EXACT position as your lens is now (before you take them apart). Position of this may be different than my lens, as each lens is calibrate individually, so MAKE SURE you mark things well!

 

[Krosya]

After you get this far, it's time to take a look inside the barrel of the lens. Look close inside that little window marked by the brackets. While doing so, turn focusing ring back and forth and at one point you will see this:

There is a little "T" shaped part that is attached wth 2 black screws. It moves with turning of the focusing ring. Basically - this is your focus limiter.

After you remove, you will be able to rotate focusing ring all the way around 360 degrees and more.

After you remove it, it's time to get the rear optical group from the barrel.

To do this, unscrew those 3 black screws at the rear of the lens - circled in a pic above. Once again - make sure you got everything well marked before doing so.

Optical group housing togethe with apperture housing will become lose inside the barrel. To remove it completely, unscrew the top part from the bottom. What you will end up with is this :

 

[Krosya]

On the left you see the rear optical group, with apperture housing, in the center - rear part of that housing, that was held to barrel with 3 black screws. and below you have barrel/focusing ring.:

 

[Krosya]

Now its time to take a look at focusing ring itself :

It's basically 3 rings. Outer, Inner, and a retaining ring that holds them together (black one)

With a spanner wrench remove black retaining ring and take inner and outer focusing rings apart:

 

[Krosya]

As you can see -there is a window there in the inner ring. This is the focus range window and this is the part that will need to be expanded to focus closer.
One end of the wndow is INF and the other is 0.9m. The 0.9m side will have to filed down to make it go to 0.7m.:

Now you ned to mark the area to be filed down:

 

[Krosya]

Now you want to attach that little "T" piece to the rear barrel assembly:

And stick it inside the inner barrel to see how this works when lens is being focused:

 

[Krosya]

Once you marked the part that needs to be filed down - do it very carefully:

When you finish, it should look similar to this:

As you can see - ALL Cosina had to do was make that window longer/wider and lens would focus to 0.7m to begin with.

You will have a lot of metal shavings after this, so make sure you clean all the parts well before re-assembly. It helps to put a bit of lubricatin between the inner and outer focusing rings.
Assemble in reverse.

When you are done your lens will do this:

Once again - this is NOT an easy modification, so do it at your own risk. This thread is just to give you some guidelines,but I make no promises as to if or how your lens will work if you chose to try this.

Hope this helps and Good luck!

 

[Krosya]

I didnt have to file down the mount of the lens - RF coupling seems to work as it as on RD1S. Will have to check with other cameras. So check with your particular bodies on this.

 

[ampguy]

very cool! awesome photos and instructions!

 

[Sonnar Brian]

Thankyou for posting these instructions. Very detailed, and great pictures.

 

[Krosya]

Update:
Having checked RF coupling on other cameras it looks like I will need to file down threads in the mount a bit to be able to have full coupling to 0.7m.

 

[Krosya]

I know what I will be doing after dinner, tonight. 🙂

So, everybody's busy modifying their Noktons? 😉

 

[ampguy]

Hi Krosya

Hi Krosya

Which ltm to m adapter are you using?

I've heard that between the cv type 1 and type 2, there is a slight thickness difference.

So if say you currently have the thicker model, perhaps the other model would be just right?

Again, very interesting stuff, even though I have a J3 right now, and not a Nokton.

Dr. Brian or Lynn will be sure to correct me here, but I believe individual adapter thickness variances may affect both the J3, and the Nokton ... 😉

Update:
Having checked RF coupling on other cameras it looks like I will need to file down threads in the mount a bit to be able to have full coupling to 0.7m.

 

[Krosya]

I have several adapters - 3 Leica, 3 Voigtlanders anda couple of cheap ones from China. Best I can tell they all perform the same. I didnt try all of them on Nokton after the modification, but based on prior experience I wouldnt expect to see any difference.

 

[P. Lynn Miller]

Thanks for all the photos and instructions. You took the long way around to make the same modification. Well done!

I will say that there is no need to remove the front of the lens, there is a short cut that I worked out so that this can all be done from the back of the lens. I did the same modification, enlarging the 'window'.

I made templates and tools to allow me to repeat the modification consistently. Cosina could have done this at no cost and with added machining time of about 2 seconds.

Thanks for all your hard work!

 

[Krosya]

I thought (after the fact) that there is a way to do it without removal of the front too, but to me it makes handling easier with front of the lens being removed. Plus I was not sure from which end of the lens I'll be able to get to things I'd need to modify, so I started from the front.
What tools did you make? I didnt need any other tools than pictured at the beginning of the thread. I wonder what is it you made to make things easier?

 

[P. Lynn Miller]

What tools did you make? I didnt need any other tools than pictured at the beinning of the thread. I wonder what is it you made to make things easier?

I tend to make tools instead of using generic tools, such as spanner wrenches. So I made the needed pin wrenches for assembly and disassembly, a hardened filing guide/template, single-sided file, etc. Basically ensures that I can disassemble, modify and reassemble in the shortest amount of time without damage and repeatable results. Just a left-over habit from my days as an armourer.

I figure I can do the modification from start to finish in about an 2 hours with my tooling and holders.

But really you do not need any special tools.

 

[Krosya]

Well, I wonder how many brave souls out there will try this modification now? Anyone?😉