Crown Graphic Fresnel?

Discussion in 'Large Format Cameras and Accessories' started by davidave, Jun 29, 2010.

  1. davidave

    davidave Member

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    Is there a way to tell if the fresnel is installed on a Crown Graphic just by looking through the ground glass? Through my research I've discovered the fresnel is a necessary focusing element, but I want to make sure *bay auctions include the fresnel.
     
  2. Bertil

    Bertil Subscriber

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    Shouldn't be any problem: open up the lens (or take it away) use a loupe and you should see the fresnel rings - if they are there!
    /Bertil
     
  3. Ian Grant

    Ian Grant Subscriber

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    Not all Pacemaker Speed & Crown Graphics came with a fresnel. The difference in overall screen brightness is quite noticeable when a fresnel's present.

    The back frame for the original screen/fresnel combination has a different register to the plain screen version because the fresnel is lens side of the screen. You can fit a fresnel to the rear on the plain screen Graphics.

    Few sellers mention whether there's a fresnel.

    Ian
     
  4. davidave

    davidave Member

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    Thanks for the replies guys. I stumbled upon another test where the guy measured the ground glass to film plane distance. He said there was about a 1mm difference and calibrated the rangefinder to compensate. He then did focus test and everything came out perfect. The conclusion was that there should have been a fresnel (about 1mm thick) in place. Makes sense!
     
  5. Ian Grant

    Ian Grant Subscriber

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    He should have shimmed the screen, which is very simple, because the screen is still out of tolerance so not accurate. So as soon a s any movements are used the range-finder is useless and the screen as well :D

    Ian
     
  6. Wade D

    Wade D Member

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    The fresnel is nice to have but not a necessity. My old Speed Graphic Anni doesn't have one and it focuses just fine. The rangefinder is spot on as well.
     
  7. Ian Grant

    Ian Grant Subscriber

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    A fresnel does make a huge difference to overall screen brightness though, over 2 stops when measured with a spot-meter.

    Ian
     
  8. Fotoguy20d

    Fotoguy20d Subscriber

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    You won't need a loupe. The fresnel is very noticeable on the inside - light reflecting off it makes a distinctive pattern. Also, you can feel it.

    Dan
     
  9. Wade D

    Wade D Member

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    I agree that the fresnel makes focusing much easier but to a practiced eye the standard ground glass works well enough. At least for me. I am planning on re-grinding the old screen using your great instructions. Never thought it would be so simple!