1975 Jupiter-8 in LTM, close-focus mod, on the EP2.

Brian S

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The J-8 is based on the pre-war 5cm F2 Carl Zeiss Sonnar, and is available in Leica thread mount and in Contax/Kiev mount.

The LTM version is normally limited to 1M close-focus. I removed the close-focus stop.

The J-8 at its normal 1M min focus, wide-open at F2, on the EP2.

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At its new closest focus.

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The infinity stop also acts as the new close-focus stop.
 

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Streetshooter

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Allright Brian,
explain how I can do that to my J8.....
I carry that lens all the time. I love the way it sees light..... I have 2 and the 1 I'd like to do this with is a '62.
Turn me on......
 

Brian S

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I will document the process for the modification- took the pictures, need to write it up. It is easier to do on the newer style focus mount, simply remove one of the stop screws. Mine will RF couple with the M8 to 0.7m, I also filed down the threads on the mount so the RF follower moves with it.

I need to look at a 1962 focus mount. I have a spare, will see if a similar trick can be done.

The 1975 lens was a 30 minute job, including filing the threads.
 

Streetshooter

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Thanks Brian, that's the only issue with the J8....close focus...
here's a image I did of my son..... it's just a fast pass thru in LR...
but it's easy to see how the lens transmits and translates light... the tones are always beautiful.....

G2 ISO 1600 f2.8 Nik Silver Effex

 

classicus

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I will document the process for the modification- took the pictures, need to write it up. It is easier to do on the newer style focus mount, simply remove one of the stop screws. Mine will RF couple with the M8 to 0.7m, I also filed down the threads on the mount so the RF follower moves with it.

I need to look at a 1962 focus mount. I have a spare, will see if a similar trick can be done.

The 1975 lens was a 30 minute job, including filing the threads.
Thanks Brian,

I have what I understand is a 2002 jupiter 8 ,which is great,
I'll appreciate if you can specify which screw...
 

Brian S

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This weekend I should have time to edit the pictures and write-up the process. I want to make one change to my lens- install a washer under the stop screw to aid in acting as a close stop. There is some resistance now where the infinity stop also acts as a near-stop, but it is possible to push past it. At that point, the lens will keep going and you have to remember to stop. although- it does get even closer focus than what is shown.
 

Brian S

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It will RF couple on my M8 down to 28" easily, and on the EP2 gets to ~18". It does as well as my LTM Nikkors, which go to 18" by design.
 

Brian S

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I took the J-8 apart last night and made an improvement: had to raise the stop screw by ~0.1mm. As originally put back together, without the close-focus stop screw, I relied on the distance-stop screw to act as both near and far stop. I got some resistance at the near end, but it was possible to push past the stop. Keep going, helical unscrewed.

Last night I ended up using some copper tape and a paper "washer" to prevent the stop screw from going all the way in. This worked much better, the lens now has a "hard" stop for the near end. It is close: if you do not put the screw in far enough, it catches and the lens cannot focus. You cannot use a washer (I tried) as it hangs up on the helical.

SO:
Step 1: take the optics module out. You are left with the focus mount.
Step 2: Focus the lens until you see the screw under the slot, will appear near infinity. (see pic1)
Step 3: Take out the stop screw under the slot.
Step 4: Unscrew the Helical. Remember where it comes apart: many ways to rethread it.
Step 5: Remove CLOSE Focus screw from the inner portion of the helical. (Pic 2)
Step 6: You will need to make shim, use a washer, etc, to prevent the first screw from going all the way in. It will be where the failed washer is in Pic 3.

You will have to experiment to get the thickness correct for the remaining stop screw to work as far and near stop.

You will also need to file the threads of the mount down about one thread. This permits the RF follower to keep up with the Cam if using on an RF camera. Of course on a u43, that step is not required.
 

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linkedit

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I was thinking of getting one of these lenses but after seeing the samples I'm having 2nd thoughts. The lens seems very flat and not all that sharp.
 

Brian S

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Jupiter-8, on the Canon P.

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My example shots in the thread are quick-and-dirty grab shots to show the close-focus mod.

A good J-8 compares well with a Nikkor-HC 5cm F2, Sonnar formula lens. Between LTM and S-Mount, I have 5 of those.
 

linkedit

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My example shots in the thread are quick-and-dirty grab shots to show the close-focus mod.

A good J-8 compares well with a Nikkor-HC 5cm F2, Sonnar formula lens. Between LTM and S-Mount, I have 5 of those.
that sample looks much better. any tips to picking a good one? i had read that sometimes the construction of these lenses isn't the greatest.
 

Brian S

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For an M43 camera, you do not worry about shiming the lens for a Leica RF.

I would go for a late black one, like this for m43. Look for one with clean glass. Should run under $50.
 
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