Velostigmat series II diffusion?

Discussion in 'Large Format Cameras and Accessories' started by athanasius80, Apr 13, 2006.

  1. athanasius80

    athanasius80 Member

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    I just got a 12 inch Velostigmat series II with the front cell diffusion ring. In testing the lens, it seems that cranking the diffusion ring changes the focus and when I refocus, I don't see diffusion, just a changed depth of field. Has anyone had similar observations?
     
  2. Russ Young

    Russ Young Member

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    Hi-
    Are you using it at the "soft" apertures- i.e., wide open or nearly so? After about f/8, it becomes pretty sharp...
    Russ
     
  3. jnanian

    jnanian Advertiser Advertiser

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    with my vitax, the diffusion ring allows you to stop the lens down a bit, and still achieve a soft image. it is a "defocus" knob and changes the placement of rear elements ... try shooting the lens wide open with the ring at different settings, and then try stopping the lens down, and re-set the diffusion ring - don't re-focus though :smile:

    i love being able to stop down to f16 and crank the de-focus knob to 3 or so, it gives a beautiful effect ...

    -john
     
  4. athanasius80

    athanasius80 Member

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    Followup: Thanks guys. Someone taped the diffusion ring somewhere in the past and I'm still looking for the number 5 on the ring and the number line on the barrel. Also, Its a 8x10 Velostigmat, and I don't have an 8x10 camera yet. I was just surprised at its behaviour on the ground glass and wanted to know what I might be doing wrong with my 5x7. Thanks for the ideas, keep 'em coming.
     
  5. Steve Hamley

    Steve Hamley Member

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    My 360mm Universal Heliar is the same - the diffusion effect is much less at smaller apertires, and "dialing in" diffusion changes the focal length and therefore focus.

    Steve