Schneider barrel mounts can have their maximum aperture adjusted!

Discussion in 'Camera Building, Repairs & Modification' started by eumenius, Feb 27, 2006.

  1. eumenius

    eumenius Member

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    Hello friends,

    today I was playing with Schneider 105/4.5 Componar. I have the cells, and the size 0 barrel (BK0, Blendenkorper 0 according to Schneider datasheet) - with maximum aperture 9. The iris didn't open completely, and that frustrated me very much. When I took the assembly apart, I found that iris can be fully opened and closed, or allowed to open just to the maximum size needed! In other words, Schneider made one barrel for all their 0-sized lenses, and changed only the aperture markings on setting ring. To adjust the max aperture, I loosened five screws on a brass keeping plate inside, and carefully moved the center ring (to which the front cell was screwed) just until the iris blades were invisible through the front, and the setting ring was on 9 stop. That was the maximum aperture - 4.5 in my case. I tightened the screws, and reassembled everything together. The result: I have a fully functional lens, the only thing I have to do is to write a new iris scale on this barrel. 9 corresponds now to 4.5, 11 is 5.6, and 64 is 32 - more than enough to me. I think the 1 sized barrel has the same scheme. So if you have a Schneider barrel mount that you would use with some other cells, you can adjust its aperture to some desired value.

    Good luck, and cheers from Moscow - Zhenya
     
  2. Donald Qualls

    Donald Qualls Member

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    The Russian genius strikes again! :smile:
     
  3. Dan Fromm

    Dan Fromm Member

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    Interesting.

    I wonder what's wrong with the Schneider barrels I've had. Three held 240/9 G-Clarons, one held 55/8 Repro-Claron, one held 135/5.6 Symmar. All had diaphragms that opened all the way and aperture scales to match the lens. So the first four opened wider that the largest marked aperture.
     
  4. eumenius

    eumenius Member

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    Dan,
    the inner construction of those barrels is typically German - plenty of unneeded complications and something important being overlooked :smile: In my barrel mount all five heads of the screws keeping the inner delimiting plate in place were damaged - quite incredible for German assembly! But I know why they're damaged - the max aperture depends on the position of the threaded ring that contains the front lens cell, so if the screws are not tight, the aperture goes off when the cell is screwed in with too much torque. There's no other stopping screws, keeping everything in factory set ordnung, can you imagine that? Only five screws and a brass thin plate keeps everything together, in an indirect way. The Schneider barrel was designed with a serious construction flaw, that's it. Maybe thanks to this flaw (the max aperture opening can be screwed up with too much torque) your barrels open up for too much. My 240/9 G-Claron barrel doesn't open to full on 9 setting, that's for sure - I got this barrel, too.