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Thread: 790mm F:5.4 LF & ULF Lens Data

  1. 14-Jun-2013, 17:48 #1
    Reinhold Schable
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    790mm F:5.4 LF & ULF Lens Data

    I needed a way to evaluate the bellows draw and image circle for a ULF lens I've been concocting.

    By commandeering my wife's sewing room, I blacked out the windows, cut a hole in a blackout that looked out over my back yard, and ...presto... a camera obscura. I rigged up a 4'x6' white sheet of plywood on a tripod to focus the image and measure bellows draw and image circle.

    Here 's a data sheet covering the image circle, bellows draw, and effective apertures at various focusing distances. Notice that it projects a 1425mm (56") diameter circle at infinity, and a circle well over 1830mm (72") !!! when focused at 3 meters (10'). The folks shooting huge wet plate and paper negative portraits should have fun with this lens.

    More later...
    Reinhold

    www.re-inventedphotoequip.com
    Attached Thumbnails Attached Thumbnails 790 data 6-13.pdf  
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  2. 14-Jun-2013, 18:02 #2
    Tin Can
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    Re: 790mm F:5.4 LF & ULF Lens Data

    You are a big tease! Now I want to make my van into a camera, or maybe make one for the roof rack.

    When will "Cet obscur objet du désir" be available?
    Tin Can
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  3. 14-Jun-2013, 18:34 #3
    Dan Fromm
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    Re: 790mm F:5.4 LF & ULF Lens Data

    Um, Reinhold, aren't you acquainted with arithmetic? The theory's well-known and well-validated, you don't have to measure (if the focal length is what you think it is), you can calculate extension.
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  4. 14-Jun-2013, 18:38 #4
    Jim Fitzgerald
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    Re: 790mm F:5.4 LF & ULF Lens Data

    Reinhold, congratulations! Can't wait. Let me know about it as my 14x17 and 8x20 lens boards await!
    Jim Fitzgerald


    http://www.jimscarbonartphotography.com


    http://www.youtube.com/watch?v=Tl5FK7PTkFw

    http://www.youtube.com/watch?v=V40Mz0mVotg


    https://youtu.be/en6Y8QaVszA
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  5. 14-Jun-2013, 19:39 #5
    Reinhold Schable
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    Re: 790mm F:5.4 LF & ULF Lens Data

    Dan... Shhhhhh, you'll blow my cover. Besides, I find it comforting to verify things with physical involvement

    Jim... Just a few small details to work out. Maybe the unveiling will be this weekend.
    So that you can prepare your lensboards, here's a drawing...

    Reinhold
    Attached Thumbnails Attached Thumbnails 790 sales dwg bw.pdf  
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  6. 15-Jun-2013, 03:28 #6
    Craig Tuffin
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    Re: 790mm F:5.4 LF & ULF Lens Data

    Happy to test one on my 20x24 for you Reinhold...or in the van and shoot a 24x32
    _______________________________________

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  7. 15-Jun-2013, 05:00 #7
    Steven Tribe
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    Re: 790mm F:5.4 LF & ULF Lens Data

    Reinhold - when you get round to making more complex lenses, get in touch.
    I can supply spherometer measurements etc. for the Darlot (et alia.) Objectif d'Artist - 3 +ve lenses and the -ve lens. All simple lenses.
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  8. 15-Jun-2013, 05:26 #8
    Tin Can
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    Re: 790mm F:5.4 LF & ULF Lens Data

    No sleep. All night designing new camera!
    Tin Can
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  9. 20-Jun-2013, 09:56 #9
    Reinhold Schable
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    Re: 790mm F:5.4 LF & ULF Lens Data

    Ta Dahhh...
    I've just posted the lens details and pricing in the For Sale section.
    Thanks for your interest and patience.
    Reinhold
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  10. 20-Jun-2013, 09:58 #10
    Tin Can
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    Re: 790mm F:5.4 LF & ULF Lens Data

    going there now

    Quote Originally Posted by Reinhold Schable View Post
    Ta Dahhh...
    I've just posted the lens details and pricing in the For Sale section.
    Thanks for your interest and patience.
    Reinhold
    Tin Can
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