Adapting a Jupiter-9 for Leica LTM, HowTo?

[johannielscom]

Hi Brian,

some time ago a US member sold a Jupiter-9 85/2.0 lens in the classifieds that was adapted to Leica LTM specs by Kim Coxon.

The Jupiter-9 on Leica LTM apparently can only be set to focus correctly on closest distance or on infinity but not both.

But, what about making it focus correctly from a certain aperture onwards when set to closest focus, and opening up more when focusing further away? Would that be feasible? Of course that would mean losing wide open close focus, but if in return it would focus correctly at say 3 mtrs and wide open, I'd go for it.

Since Kim is rarely here and you are the Sonnar guru (deep bow), could you help me out by describing what should be done to a Jupiter-9 to make it come to terms with Leica LTM?


I'd be interested in pictorials and the likes, too!

 

[ferider]

Johan,

there are two shims in the Jupiter 9: one for infinity collimation, one to move the rear element group. By changing both shims (and changing the focal length), some J9s can be collimated perfectly from min focus to infinity; some can not, because the rear el. group has to be moved forward so much that the lens will collide with the aperture ring when focusing. It's a gamble. Most J9s that I have seen (around a dozen ?), have the second shim completely removed, I'm assuming to get as close to optimum as possible.

Contact Kim directly - he's the expert. Not that Brian is not, but for the 85, Kim might be able to help you. He also published a manual for doing this, with photos.

Roland.

 

[johannielscom]

Allright, some math then!


Russian standard lens is 52.4mm, Leica is 51.6mm (both say '50' at the front).

That is a factor 1.01550 that the Russian standard is longer.

Apply that to 85mm (divide 85mm by 1.01550) and it should mean that the focal length should actually be shortened to 83.7mm to make it work on Leica LTM. Right?

Now would that mean that a lens shortened to a focal length of 83.7mm would stay accurate while focused throughout its range? Or would it still 'wander off' throughout the range?



I'll get in touch with Kim to ask for that manual, Roland!

 

[ferider]

... Now would that mean that a lens shortened to a focal length of 83.7mm would stay accurate while focused throughout its range? Or would it still 'wander off' throughout the range?

I'll get in touch with Kim to ask for that manual, Roland!

Yes, Kim had luck with some lenses being able to focus them throughout the range. I think in some cases he had to grind down the aperture ring.

Found his manual, BTW:

http://www.pentax-manuals.com/repairs/j9service.pdf
http://www.pentax-manuals.com/repairs/j9collim.pdf

Your other option is to find a very early Jupiter from 1951 or so, or a ZK 85/2 (I once had one). Only downside is that it has min. focus 1.8m, just like the original Sonnar.

Roland.

 

[Sonnar Brian]

The chrome J-9's only have one shim, the main one. The rear module looks like "fit and finish" on individual lenses.

the Black J-9's have a secondary shim for the rear module.

I tried 3 different J-9's, moving the rear module to reduce the focal length and then adjusting the main shim. "limited range Zoom". Change focal length, then compensate.

There was just not enough space in the optics module to reduce the focal length enough to focus across the entire range.

http://www.rangefinderforum.com/forums/showthread.php?t=79337

I sold the lens in this thread to someone just wanting it for portraits.

 

[johannielscom]

The J-9 has a double helical, and translates the motion for the 8.5cm focal length to the RF cam. The translation produces the same travel on the RF Cam that a J-3 or J-9 lens would produce, ie for a 52.4mm focal length lens. The Leica standard is set up for a nominal 51.6mm travel. The travel on the RF cam of the Russian lens is ~0.1mm more than a Leica is set up for. Reducing the focal length of the J-9 slightly means the required travel for the focus across range is less, and that lines up with the J-9 monted on a Leica.

That's my story, and I am sticking to it...

So Brian,

according to the above quote from that thread you linked to, my calculation of reducing the focal lens length to 83,7mm would/could be correct?

 

[Sonnar Brian]

Go for it!

I have not had morning coffee... The nominal focal length in the Spec sheet for the J-9 is 84.5mm. Use that for a starting point, and give it a try.

 

[johannielscom]

Go for it!

I have not had morning coffee... The nominal focal length in the Spec sheet for the J-9 is 84.5mm. Use that for a starting point, and give it a try.

Actually I went for it early this morning, albeit in a slightly different fashion:

JUPITER-9 2/85 M39 LEICA ZORKI FED SONNAR GLASS SILVER. S/N OF LENS 5100582. It was made in 31.05.1951 in krasnogorsk factory from german sonnar optical block. Lens has original passport. Optical block has number on body, 840054. I have many lenses of this year and only this number has a sonnar lens.

Quote from the ad I bought this from:

I had some savings for a Hektor 73mm from the Westlicht auction but it went way past my budget. This one didn't!

 

[ferider]

I have a good feeling about this one, Johan. Note the effective focal length on the passport (83.7 ?).

That being said: I had similar cravings as you seem to have: my pick was the Komura 80/1.8, also from the 50s, an Ernostar 🙂

Roland.

 

[B-9]

Any updates? Interesting to see what has come of this project!

 

[johannielscom]

Nothing has come of it since I bumped into a lens that fit the bill straight out of the factory!

And, to get more crazy, I'm selling said lens in the classifieds as of tonight! 😱