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Thread: fresnel screens

  1. #1

    Join Date
    Sep 2004
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    fresnel screens

    I know this has been discussed before, but I'm confused about what I have. I just purchased a Linhof Technikardan 45 that came with a frensel screen. However, the screen assembly seems to be a little different from what I have read about here before. The fresnel screen (plastic) is on the film side of the glass with the circular grooves facing the film. On the back side of the fresnel screen is a piece of clear glass (not frosted) with a grid on it. For you Technikardan people, the gridded glass is held in place with the two screws (one on top and one on bottom) and the fresnel screen is in a type of narrow frame that seems to be held in place with the four other screws (in the corners). It all seems to be installed as the camera is designed for.

    I assume that a ground glass is normally installed by the two top and bottom screws and with the back of the fresnel screen in contact with the front surface of this clear glass, it seems to me to be correctly installed. However, there may be a slight gap or space between the two surfaces - it is impossible to determine.

    The screen is very bright and will be a definite improvement over my older 4x5 with standard ground glass.

    Does this all sound like it's installed properly. From what I have read here before, it has been said to install the fresnel screen on the back side of the glass not on the film side, however, for this type of setup, maybe it's done correctly.

  2. #2

    fresnel screens

    Maybe Bob Solomon from HP Marketing will chime in here.

    Linhof sold these fresnels that were as you said, installed under the ground glass for several years and have a new and improved version that is supposed to prevent the tendency to separate/warp.

    My Master Technika came with one of the older versions of this fresnel and because mine had a similar separation that prevented consistent focus, I was forced to send it to Marflex (the Linhof repair agent) to have it removed and have them install the rear mount (behind the ground glass) fresnel. Marflex had to re-calibrate the ground glass because the under the ground glass fresnel has a different registration. I believe that I got the Linhof fresnel from Badger for about $100 and it was held in place behind the ground glass with side screws and clips.

    The new fresnel works fine for me. Have fun with the TK45. Great camera.

  3. #3

    fresnel screens

    Sounds like you have the Beatti screen. It is what I have on my TK and it sounds exactly like the same set up. If the screen was placed correctly, you are going to love it.

  4. #4

    fresnel screens

    I should have added, if the previous owner messed up with the 4 screws that hold the fresnel lens, then you will not register the film plane with the focus plane. OTOH if he did not mess with them, you should be fine. The way Beatti set it up, the fresnel lens should be on the film side and the piece of glass covering it. I guess this was done to protect the fresnel as it is very delicate and placing a loupe on it would scratch it.

  5. #5

    Join Date
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    fresnel screens

    A modern Linhof camera (Technika IV to the current 4x5 modelas) have 4 small adjustable shims, one in each corner, that the ground side of the ground glass sits on. The ground glass is held in place on each end with a black metal strip that is mounted to the back with 3 screws in each. Under the center screw on each strip there is a moving stainless clip the holds the fresnel in place, grooved side down.

    The Linhof Super Screen is plastic and has grooves on one side and a frosted surface on the other. The frosted side faces the film and the grooved side faces up. To protect the grooves a glass overlay with grid was available as an acessory and is placed on top of the Super Screen and is held in place with the stainless clips or it is placed diretly on top of the Super Screen and is held in place with the black metal strips with the 3 screws.

    " the gridded glass is held in place with the two screws (one on top and one on bottom) and the fresnel screen is in a type of narrow frame that seems to be held in place with the four other screws (in the corners). It all seems to be installed as the camera is designed for."

    This is not the way a Linhof is designed.

    " The fresnel screen (plastic) is on the film side of the glass with the circular grooves facing the film."

    This can mean that someone has played with the proper settings for the shims. What you are describing is not a Linhof gg or a Super Screen.

  6. #6

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    fresnel screens

    "Linhof sold these fresnels that were as you said, installed under the ground glass for several years and have a new and improved version that is supposed to prevent the tendency to separate/warp"

    No, you are confusing the old Linhof camera screen placement where the groundglass we placed over the fresnel.

    The Super Screen replaced both the fresnel and the groundglass as a one piece, non-sandwiched piece. It was covered by the CM Grid screen to protect the grooves of the Super Screen which was positioned with the grooved side torward the eye.

    A fresnel screen is properly positioned grooved side torwards the lens.

  7. #7

    Join Date
    Nov 2003
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    fresnel screens

    I don't have a Linhof, but my Maxwell screen is installed that way. With a Fresnel facing the film, it is possible that there is a slight focus shift. I've seen 1/3 the thickness of the screen as the estimate. If the camera is new to you, it might be a good idea in any case to check that the focus plane of the screen and that of the film are close enough. It is never possible to get them exactly the same but the difference should be very small, certainly within the limits of normal focusing error.

  8. #8

    Join Date
    Sep 2004
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    fresnel screens

    Thanks everyone for your help. It sounds like this is clearly not a normal Linhof accessory installation. I'll need to do some careful testing to see if everything is in register.

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