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Thread: A DIY 177mm f/8 Cooke triplet for 4x5 from off-the shelf lenses that YOU can build

  1. #91
    Tim Meisburger's Avatar
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    Re: A DIY 177mm f/8 Cooke triplet for 4x5 from off-the shelf lenses that YOU can bui

    Looking good! It will be really interesting to see a portrait, when you have it complete.

  2. #92
    Nodda Duma's Avatar
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    A DIY 177mm f/8 Cooke triplet for 4x5 from off-the shelf lenses that YOU can build

    Thanks.

    Flange focal length (distance from the outside mounting flange to image plane) measures ~ 165mm. Reversed, focal length measures 200. Very rough measurements of course. Maybe I'll have a 2-step zoom

    Next I'll either pull the optics to machine the slot for the waterhouse stops, or make a lensboard to mount it to my camera. Slow and steady, or go for broke? Decisions, decisions...

  3. #93

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    Re: A DIY 177mm f/8 Cooke triplet for 4x5 from off-the shelf lenses that YOU can bui

    sounds like you are going slow and steady then?
    ~nicholas
    lifeofstawa
    stawastawa at gmail

  4. #94
    Nodda Duma's Avatar
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    Re: A DIY 177mm f/8 Cooke triplet for 4x5 from off-the shelf lenses that YOU can bui

    No I think I'll put it on a camera first...just have not had the time to work on it

  5. #95
    Nodda Duma's Avatar
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    Re: A DIY 177mm f/8 Cooke triplet for 4x5 from off-the shelf lenses that YOU can bui

    First light!

    Acquired a Burke & James press camera which accommodates a lens board sufficiently large for the lens. This allowed me to capture an image on one of my homemade glass plates coated with a homemade emulsion. This particular exposure was 3 minutes (it was getting dark) wide open at f/8.

    Click image for larger version. 

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    I'm pretty sure my focus is slightly off due to the difference in distance from lens to the emulsion plane for a glass plate (0.050" thick) and for sheet film (~0.0075"). I focused the words of the license plate while viewing ground glass with a loupe to be centered in the depth of focus, but the license plate appears to be at the outer edge of the depth of focus in the image. The can blocking the plate number is about 6" wide and is completely within the DOF. Still, it allows some fair judgement of image quality -- which is close to prediction -- and bokeh, which is difficult to analyze in Zemax.

    Next test will be for object distance much further. Or a portrait. I think this would be a good portrait lens.

  6. #96
    Peter De Smidt's Avatar
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    Re: A DIY 177mm f/8 Cooke triplet for 4x5 from off-the shelf lenses that YOU can bui

    Great job!
    "Why can't we all just get along?" President Dale, Mars Attacks

  7. #97

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    Re: A DIY 177mm f/8 Cooke triplet for 4x5 from off-the shelf lenses that YOU can bui

    There is an online machine shop emachineshop.com which provides a design tool to use in designing parts and generating quotes. Perhaps that would be an option.

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