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Thread: Speed Graphic inaccurate focus

  1. #11

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    Re: Speed Graphic inaccurate focus

    Quote Originally Posted by Jim Jones View Post
    Another problem occurs when adding a non-OEM GG to a Graphic: it may not be the correct thickness.
    Shouldn’t make a difference as long as you place the ground side in the proper position in the back. What could displace focus would be replacing the fresnel on the camera with a thicker then one when the fresnel is under the gg.

  2. #12
    Serious Amateur Photographer pepeguitarra's Avatar
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    Re: Speed Graphic inaccurate focus

    My Super Speed Graphic came with a fresnel from factory, and it is placed between the lens and the ground glass. The Fresnel circles are in contact with the ground side of the ground glass. How do I know, I have the factory manual that shows the position. I got the manual in the internet after trying to be smart and removing the fresnel from there and putting it outside the camera on the smooth side of the ground glass. I got out of focus images. I had to go and put it back the way it was and indeed, it was like that from factory. In fact the Super and the Super Speed Graphic came like that, see a screen shot from manual.

    Fresnel by Palenquero Photography, on Flickr

  3. #13
    Serious Amateur Photographer pepeguitarra's Avatar
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    Re: Speed Graphic inaccurate focus

    The whole page on this subject:

    part1 by Palenquero Photography, on Flickr

    part2 by Palenquero Photography, on Flickr

  4. #14

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    Re: Speed Graphic inaccurate focus

    Yes, Pepe, that's what Graflex Inc. and successors intended.

    But Pacemaker Graphics were introduced before Graflex installed fresnels ("Ektalite field lens") in their cameras. When Graflex introduced the Graflok back in 1949 focusing panel fresnels were optional. I b'lieve they were standard issue for 3x4 and 4x5 Graphics by 1954.

    That's one of the reasons that people with Graphics get into trouble with aftermarket or retrofit fresnels. As I mentioned, there are two different panels, one with high bosses (no Graflex-issue fresnel), the other with low (Graflex-issue fresnel). Both have the same casting number.

  5. #15
    Nodda Duma's Avatar
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    Speed Graphic inaccurate focus

    Quote Originally Posted by Bob Salomon View Post
    Shouldn’t make a difference as long as you place the ground side in the proper position in the back. What could displace focus would be replacing the fresnel on the camera with a thicker then one when the fresnel is under the gg.
    It does due to combination of converging rays and change in optical path length (index of refraction * glass thickness)


    Dan: Good tidbit of info on bosses and I’ll check mine out tonight.
    Newly made large format dry plates available! Look:
    https://www.pictoriographica.com

  6. #16

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    Re: Speed Graphic inaccurate focus

    Quote Originally Posted by DocTranimal View Post
    I got a Speed Graphic a while back and have been noticing that all of my shots are soft where I focused and sharp about 1 inch front of where I focused.

    When I got the camera, it had the OEM fresnel and ground glass. I've been doing tests with pack film and with or without the fresnel, And the problem is the same with all of my shots.

    What's going on? This is frustrating.
    Are you using a loupe? If so, have you focused it on the grain side of the gg?

  7. #17

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    Re: Speed Graphic inaccurate focus

    A thought - does it suffer from the same issue as my MPP? The ground glass is at 5.08mm, but the Fidelity film holders put the emulsion at the current standard 4.80mm. The ground glass is positioned for the plate holders I bought with the camera.

    Neil

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