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  1. #21
    jstraw's Avatar
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    Does anyone know how much gap between the two panes is too much?

  2. #22

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    "It is recommended that something, perhaps tape, be used to create a gap between the two panes so that there is not tight contact between the AN glass and the base side of the film, true?"

    I'm not sure about this. My only past experience with ANR glass has been with it pressing firmly on the negative--that being in Leitz Focomat 35mm enlargers. I recently bought a universal glass negative carrier for my current LPL but I haven't used it yet and it also presses tight against the negative.

  3. #23

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    Quote Originally Posted by Lee Shively View Post
    "It is recommended that something, perhaps tape, be used to create a gap between the two panes so that there is not tight contact between the AN glass and the base side of the film, true?"

    I'm not sure about this. My only past experience with ANR glass has been with it pressing firmly on the negative--that being in Leitz Focomat 35mm enlargers. I recently bought a universal glass negative carrier for my current LPL but I haven't used it yet and it also presses tight against the negative.
    I think my devere carriers press the film quite tight and have not had probs. The emulsion side tends not to be too shiny and so is not a source of rings normally. Its the top (base) which is the prob esp with very shiny modern films such as Acros, Tmax 100, Neopan 400 or some oldies like Pan F. I have heard of some having rings even with AN glass but I guess all AN glass is different so you will prob have to test. My Durst 138 has no AN glass andd I still dont have probs but this exerts far less pressure than the devere which has the head weight effectively bearing down on it.

  4. #24
    jstraw's Avatar
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    If the correct approach is for the negative to be sandwiched tightly between the lower, normal glass and the upper, AN glass then I can use black tape to do the masking un the underside of the bottom glass.

  5. #25
    Loose Gravel's Avatar
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    If the glass above is not touching the neg, then it is not flattening the neg and it then would have no purpose. It would seem that if you are going to use a double glass carrier, then the neg needs to be compressed between the glass. As the glass and the neg get within a few multiples of the wavelength of light, it becomes important that the glass be ANR, or better yet with diffusion, diffuse.

    I don't use glass much, but it would seem that the curvature of roll film with its high enlargement ratio and bigger f/# would be more of a problem than a naturally flat piece of sheet film under low magification and small f/#.

    Anybody done the numbers on DOF during enlargement? What is the curvature of field for enlarging lenses -- trivial?
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  6. #26

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    Quote Originally Posted by Loose Gravel View Post
    ...What is the curvature of field for enlarging lenses...
    I thought that enlarging lenses were flat-field, i.e. with no curvature?

  7. #27
    David A. Goldfarb's Avatar
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    "Flat field" usually means "relatively flat within a certain range of magnification," and enlarging lenses are designed to fit that description for typical use (or sometimes special use in the case of lenses like the Rodagon G lenses for mural sized enlargements).
    flickr--http://www.flickr.com/photos/davidagoldfarb/
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    Academic (Slavic and Comparative Literature)--http://www.davidagoldfarb.com

  8. #28

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    I guess we're hijacking the thread so I apologize but I also now have a question concerning glass carriers.

    In my previous experience with Leitz enlargers , the negative carriers were open at the bottom with an ANR glass ring at the top and they held the negatives very flat. The universal LPL carrier (for 35mm thru 6x7) I just bought has glass on both the top and bottom. I'm wondering if the bottom piece of glass is necessary?

  9. #29
    Jon Shiu's Avatar
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    Quote Originally Posted by Lee Shively View Post
    I guess we're hijacking the thread so I apologize but I also now have a question concerning glass carriers.

    In my previous experience with Leitz enlargers , the negative carriers were open at the bottom with an ANR glass ring at the top and they held the negatives very flat. The universal LPL carrier (for 35mm thru 6x7) I just bought has glass on both the top and bottom. I'm wondering if the bottom piece of glass is necessary?
    Hi, the glass is necessary to prevent the negative from falling through the neg carrier.

    Jon

    Alright, the bottom glass is necessary to support the film, otherwise it will sag. I didn't mean completely fall through.
    Last edited by Jon Shiu; 01-10-2007 at 09:29 PM. Click to view previous post history. Reason: to clarify my post
    Mendocino Coast Black and White Photography: www.jonshiu.com

  10. #30

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    Not really. The masking blades would prevent this. Also, negative strips extend into the metal frame area where they are also held in place.

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