My first large format camera - a Crown Graphic - question about ground glass removal

Discussion in 'Large Format Cameras and Accessories' started by Todd Barlow, Aug 19, 2012.

  1. Todd Barlow

    Todd Barlow Subscriber

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    I have acquired a Crown Graphic 4x5 and I have a few questions:

    1) From my research the back it came with is a Graflok back (see photo 3) - correct?
    2) It appears that the ground glass is sitting on top of a fresnel screen (see photo 2)
    3) I would like to clean the ground glass - based on your experience is it as simple as removing the brackets shown?(see photo 1) Any shims or other smaller parts I have to be on the look out for?
    4) Have read alot about the cleaning and soap and water comes up the most for both the GG and the Fresnal - based on your experience any advice you would pass on.

    Clean the GG, test the shutter speeds, test the bellows and then load my first film in the holders and I think I will be ready for the field test.

    Thank you in advance for your insight and help.

    Todd
     

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  2. Ian Grant

    Ian Grant Subscriber

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    Yes ot's aGraflok back, removal of the screen and fresnel is very easy and there's no shims normally. I clean with liquid detergent & warm water followed by a rinse with glass cleaner, this leaves it with no smears. Reassembly is easy :D

    Ian
     
  3. Jon Shiu

    Jon Shiu Subscriber

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    Yes, just take the clips off and wash with soap and water, rinse, and dry with a towel. When removing, take note of how the glass is positioned: I believe fresnel below with lines facing up, then ground glass on top with frosted surface down.

    Jon
     
  4. mopar_guy

    mopar_guy Subscriber

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  5. jnanian

    jnanian Advertiser Advertiser

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    if you want a "grid" so you can align things
    or so you can mark where a 6x6 or 2x3 or? rollfilm holder
    would be to make your composition that much easier ..
    make a grid on a sheet of paper and go to your friendly
    copy shop and have them print it on clear film, its cheap :smile:
    just slide it on top of your glass under the clippy things
    and there you go, an inexpensive grid ...

    have fun !
     
  6. ChuckP

    ChuckP Subscriber

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    Be careful washing the Fresnel screen. It's easy to scratch it. Just take it easy.
     
  7. Captain_joe6

    Captain_joe6 Member

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    I don't know about that order. There were a lot of rumblings about the Chamonix cameras and their old practice of putting the fresnel under the ground glass, which lead to improper focus as the ground glass was not at the film plane, but the fresnel was. They've since changed things and started putting the fresnel on top.

    I don't want to claim authority on this one, since I'm far from it. I'm just spouting off that every other camera I've seen with a fresnel has had it on top. YMMV, of course.
     
  8. Ian Grant

    Ian Grant Subscriber

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    Jon Shiu is 100% correct about the order for the Crown/Speed & Super Graphic where the original back came with a fresnel. They have the correct spacing.

    Chamonix made a huge error in manufacture because they hadn't taken the extra thickness of a fresnel into account which shifts the focus plane consequently their first batches of cameras had a focus error mainly only seen when shooting at wider apertures.

    Fresnels below the screen are quite common Graflex, Linhof, Wista and many others have all used them this way, current Lihnof models use them on top though.

    There are some Graflex backs (usually spring backs) that had no fresnel (from new) the castings are almost identical except the 4 corner pillars which support the ground glass but the OP's clearly not got this back.

    Ian
     
  9. Dan Fromm

    Dan Fromm Member

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    You're right about the Chamonix catastrophe, as Ian has already pointed out.

    You're mistaken about Graphics. Graflex Inc started offering a fresnel with Graphics (Pacemaker Speed, Pacemaker Crown, Century) when they introduced the Graflok back in 1949. It was an option. As Graflex sold them, the fresnel went between the ground glass and the lens.

    This is absolutely not to say that it is safe to put a fresnel in front of the GG in a Graphic focusing panel that was sold without a fresnel. If you dismantle a Graphic focusing panel, you'll see that the GG (and fresnel, if one is there) sits on bosses at the sides of the gate. Focusing panels made to have a fresnel-GG sandwich mounted have low bosses, focusing panels made to have only a GG mounted have high bosses. There's one focusing panel casting for each size of Pacemaker Graphic (2x3, 3x4, 4x5); the bosses on focusing panels that have fresnels were milled down. So, the focusing panel's casting number carries no information about whether the panel want the sandwich or a GG without fresnel.

    Practical implications: if the FP has the sandwich, assume that it is original and make sure that the fresnel is between the GG and the lens, also that the ground side of the GG faces the fresnel. If the FP doesn't have the sandwich and you want a fresnel, put it between the GG and the film.
     
  10. Ian Grant

    Ian Grant Subscriber

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    I think you mean between the Ground Glass screen and the eye.

    In practice if you add a fresnel to a Crown/Speed Graphic Focus pane that never had one you add it eye side of the GG with the fresnel side against the glass, you need to shim the retaining clips otherwise the focus hood won't fit securely.

    Ian
     
  11. BradS

    BradS Subscriber

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    just to add a monkey wrench to the soup, I once had a Pacemaker Crown Graphic that came with no fresnel but, there were shims under the ground glass to compensate for the absense of the fresnel.
     
  12. Dan Fromm

    Dan Fromm Member

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    Ian, thanks for the correction. Of course you're right.
     
  13. Captain_joe6

    Captain_joe6 Member

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    Well, I suppose that'll teach me to go questioning the graflex guys... :wink: