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1950 KMZ J-3: first infocus images from a very early Jupiter.

Discussion in 'Projects/Repair' started by Brian, Apr 6, 2012.

  1. Brian

    Brian SC Top Veteran

    638
    Jul 7, 2010
    This 1950 KMZ Jupiter-3 was originally made in Contax/Kiev mount, and looked like it had never been used. It probably was not.

    [​IMG]

    The focus was way off, the optics module was held in with sewing thread, there were no shims to remove to correct the front-focus problem, and some set screws were never put in. This lens is a mix of Russian and German parts which just did not work together.

    I put it into a KMZ LTM mount, shimmed for optimal use close-up and wide-open.

    [​IMG]

    Wide-open and close-up on the M9:

    [​IMG]

    Probably the first in-focus portrait ever made with the lens.

    The focal length was way off, and the lens could not be reliably used past about 10ft.

    [​IMG]

    Focus on the fence, tree behind it is in better focus. Infinity focus was unusable. Actual focus fell behind the RF as you moved to infinity. The focal length was much too short for a Leica, and would be even worse on a Contax. The field curvature also seemed very high- focus at edges was much closer than that in the center.

    First Jupiter-3 that I’ve ever had to increase the focal length. This is done by moving the rear triplet out.

    [​IMG]

    I used Teflon tape made for plumbing applications. This is a trial-and-error process, move the rear element and then change the main shim to get the focus correct for both close-up and infinity. Digital cameras are great for this. It took about four attempts to get the focus where it is now. When finished, an extra 0.15mm was required for the main shim, and the rear triplet was moved out about the same. The focal length was increased about 1mm, based on the extra 0.15mm required for the main shim.

    Close-up, and wide open:

    [​IMG]

    [​IMG]

    and distance at F1.5:

    [​IMG]

    The focus is fairly even across the fence, the field curvature seems to be tamed. I believe the spacing for the optics is now closer to the intended design, aberrations are not as wild.

    [​IMG]

    This lens seems to be the “missing link” between ZK Sonnars and Jupiter-3’s. Or it was assembly practice. I had another 1950 J-3 that was much like this one, but the focal length was much too long and the rear triplet could not be moved in far enough to correct the error. I parted it out. Two 1951 J-3’s: fixed one by moving the front optics to a new fixture and a new rear triplet, fixed the second by changing the rear triplet. I don’t know if all of the early J-3’s had issues, but the four that I’ve worked on were unusable. The 1953 J-3’s: all five that I’ve shot with were as good as the wartime Zeiss Sonnars.
     
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  2. Brian

    Brian SC Top Veteran

    638
    Jul 7, 2010
    Cherry Blossoms, F1.5

    [​IMG]

    At F4, some focus compensation for Sonnar Shift:

    [​IMG]
     
    • Like Like x 1
  3. Brian

    Brian SC Top Veteran

    638
    Jul 7, 2010
    Dogwood again, F1.5

    [​IMG]

    Sonnar Signature. The Serial Number on the rear module dates the lens to a batch of 5000 5cm F1.5 Carl Zeiss Jena Sonnars, shown finished in April 1945. I suspect a lot of lenses in various stages of manufacture were taken back to Russia, this was one of them.
     
    • Like Like x 1
  4. Armanius

    Armanius Bring Jack back!

    Jan 11, 2011
    Houston, Texas
    Jack
    As always, I love reading about your lens rehabilitation stories!
     
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  5. pictogramax

    pictogramax SC Top Veteran

    978
    Aug 18, 2011
    Belgrade, Serbia
    I admire your skill! And love the look you got from that rescued lens. Bravo!
     
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  6. nicodemus3d

    nicodemus3d New to SC

    9
    May 5, 2012
    Hi Brian,

    The bloom photos are lovely. I'm massively jealous that you've got your hands on such a nice pristine lens body. I've recently picked up a version of the Jupiter 3 and am completely in love with it.

    I've read on other forums that a close-focus mod is possible for this lens but sadly the pictures from those threads are no longer available so I can't look into trying the mod out myself.
    Do you happen to know anywhere I could get the focus mod done?

    Many Thanks

    -Mike
     
  7. Brian

    Brian SC Top Veteran

    638
    Jul 7, 2010
    I need to find those pictures again- until then,

    Take off the focus ring by undoing the three set screws. Then, three set screws hold the helical into the mount (one screw on early J-3's).

    Take out the helical- you will see a set screw that travels in a slot that acts as the stop for close-focus and infinity focus. Take it out, the lens will focus to ~0.8m.

    [​IMG]

    The Guide Screws in the helical will act as the close-focus stop with this screw gone. You can also file down the guide slots to go even closer. The threads of the mount will also have to be filed down for the RF follower to keep contact with the cam of the lens.
     
  8. nicodemus3d

    nicodemus3d New to SC

    9
    May 5, 2012
    Thank you for taking the time to reply Brian, your knowledge is much appreciated.

    I've removed the focus ring and the mount.

    I've found the screw. Although I originally got confused thinking it was one of the 2 screws that are 180 degrees to each other.
    Even after removing the mount and helical, there doesn't seem to be enough room to extract the screw through the gap. I there a special technique to this? It unscrews most of the way but starts bumping into the thread below it before it completely comes free.

    BTW, I thought I'd give the focus a clean and lube whilst the lens is disassembled. Is there any particular lube I should use for the focus?


    I remain unclear as to what part I should file down?

    Sorry for the barrage of questions on a Sunday morning and for hijacking your thread :rolleyes:

    Thanks

    -Mike
     
  9. Brian

    Brian SC Top Veteran

    638
    Jul 7, 2010
    On mine, there is a cutout for access to the screw- I think it was at infinity focus. You might need to separate the inner/outer helical. The screws in the guide slot come out, allow the helical to unscrew. be sure to scrobe marks in each side of the inner/outer helical near the guide rails. There are multiple starting positions, including one that allows full throw but is 180 degrees out of phase. The red dot for aperture will be off if you do not get it back to original starting point.

    I use white lithium grease, found at hardware shops.
     
  10. nicodemus3d

    nicodemus3d New to SC

    9
    May 5, 2012
    Yes I think I'll need to separate the inner and outer helicals to get the screw through the gap.
    I'll make sure to mark the points so that I can put it together again

    Do you happen to have a photo showing which thread needs to be filed down?
    It's really interesting to get to see and understand how these lenses operate. There are still huge gaps in my understanding though.
     
  11. Brian

    Brian SC Top Veteran

    638
    Jul 7, 2010
    A comparison of the mount of the j-3 focus mount used for this lens and a regular lens:

    [​IMG]

    And typical scibe marks that I make to get a helical back together after cleaning.

    [​IMG]

    Helical is the one i used for the 1950 J-3 conversion.
     
  12. Brian

    Brian SC Top Veteran

    638
    Jul 7, 2010
    Have plenty of Q-Tips, paper towels, Ronsonol, and Isopropyl alchohol for cleaning.

    [​IMG]
     
  13. nicodemus3d

    nicodemus3d New to SC

    9
    May 5, 2012
    I chickened out on the focus mod in the end. Settled for a good clean and re-lube of the focus. I'm just too scared to damage this little gem
     
  14. Brian

    Brian SC Top Veteran

    638
    Jul 7, 2010
    I don't blame you- when these lenses were $50 each, much easier to take a risk.

    The downside of the close-focus mod, infinity focus suffers. The 1950 lens is "out of spec", the focal length was too short. Most J-3's have a focal length longer than the Leica standard. Optimizing for 1m and wide-open means stopping down to F2.8~F4 for infinity focus. But optimizing for 0.8m, distance focus starts to suffer around 5m.