Sinar fresnel lens question?

Discussion in 'Large Format Cameras and Accessories' started by Dave Dawson, Mar 26, 2009.

  1. Dave Dawson

    Dave Dawson Member

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    Hi All, Please excuse this what might seem to some a very basic question but all the LF cameras I have used in the past have had their fresnel lens inside the camera with the grooves in contact with the ground surface of the focusing screen. However it appears that with the Sinar F,C,P range the fresnel fits on the outside of the camera behind the gg screen.

    My question is....Doesn't that give TWO focusing points?:confused:

    Please put me out of my misery gently:smile:

    Cheers Dave in London
     
  2. Ian Grant

    Ian Grant Subscriber

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    No, the focus is always on the ground glass, the fresnel is only altering the direction of the light in these screens not offering magnification. It does matter which way the particular back is designed to take the fresnel as that can afect focus if you place the combination the wrong way around.

    Ian
     
  3. Dave Dawson

    Dave Dawson Member

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    Ahhhhh, So the concentric rings of the fresnel are in contact with the smooth side of the gg screen...Correct ?
     
  4. archphoto

    archphoto Member

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    Yes, that should be right.
    I have had it this way for 20 years on my Sinar P2.
    Having it the other way around would mean that you damage the fresnel when focussing with a magnifier.

    Peter
     
  5. Dave Dawson

    Dave Dawson Member

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    Now I understand....Thanks Ian and Peter........Job done.

    Cheers Dave