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Thread: Rapid Rectilinear Spacing

  1. #1

    Rapid Rectilinear Spacing

    I happened to run across the unmarked front and rear mounted cells of a large old lens and, what the heck, for $12.50 including the brass shade, I didn't even argue over the asking price. A cursory examination makes me guess that it was about an 18 inch f/8ish RR. Does anyone have one mounted (Jim? Ole?) who could tell me the spacing? Or, would anyone have a formula or even a guess as to the proper spacing range before I go into barrel making mode?

  2. #2

    Join Date
    Dec 2006

    Re: Rapid Rectilinear Spacing

    just from experience with similar lenses I'd say about 70mm. You would have to measure the exact same lens to make sure.

  3. #3

    Join Date
    Sep 2003
    Harbor City, California

    Re: Rapid Rectilinear Spacing

    Since they are unmarked, how about sticking the cells in some sort of plastic plumbing tube temporarily and see what results? Not very scientific, but it could vbe interesting.

  4. #4

    Join Date
    May 2004

    Re: Rapid Rectilinear Spacing

    The formula is here (equation 1.16 or 1.17):

  5. #5

    Re: Rapid Rectilinear Spacing

    Uli, I ran the numbers and, Wimpler, 70mm is as good as anything. Minor variances just change the combined focal length a little. I made a barrel out of a cardboard mailing tube and mounted it in an extra board I had. I just tested it on the camera and it is now a 19 ½ inch f/8 lens. Looks pretty good on the ground glass with just a little "glow". I'll give it a try wide open then decide if I want to work out some stops for it. Thanks for the input.

  6. #6

    Re: Rapid Rectilinear Spacing

    Oh, and Ernest, I checked out the plastic plumbing tubes and, as the lens threads are a bit larger than 3 inches, I thought it would be easier to rough out a 3 inch mailing tube than the heavy plastic.

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