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Thread: Make your own helical focus mount

  1. #11

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    Re: Make your own helical focus mount

    I can understand your desire to make your own. But there are some major issues that you have to solve to make this work. The first is the FFL of your lens. If the helical is too long you can't focus to infinity. And if it too short you will also have a focusing problem in that you won't be able to focus to infinity unless you make an extension for the lens board to make the helical the correct FFL when it is fully retracted. How will you calibrate DOF and distance settings? Then the helical has to be large enough so the rear element fits inside it. These would eliminate nearly all MF helicals and most "junkyard" helicals.

  2. #12

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    Re: Make your own helical focus mount

    Quote Originally Posted by Bob Salomon - HP Marketing View Post
    I can understand your desire to make your own. But there are some major issues that you have to solve to make this work. The first is the FFL of your lens. If the helical is too long you can't focus to infinity. And if it too short you will also have a focusing problem in that you won't be able to focus to infinity unless you make an extension for the lens board to make the helical the correct FFL when it is fully retracted. How will you calibrate DOF and distance settings? Then the helical has to be large enough so the rear element fits inside it. These would eliminate nearly all MF helicals and most "junkyard" helicals.
    Ahh I am a builder guy. These are part of the enjoyable part to make something work. All these problems can be solved. Heck, I am finishing up on a 6x30 camera. Have you heard about one of those? But thanks for the concern. You do have some justification here. The lens rear element won't be a problem for medium format helicals but the helical does have to be short. If the helical is too short I adjust the rest of the camera/cone to fit. Too long...I will machine off the extra bit.

  3. #13

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    Re: Make your own helical focus mount

    I go along with Darcy, to do this kind of stuff you really have to think outside the box.
    If you want to go crude, use telescoping sections of PVC pipe. One section or the other could be sanded down & lined with velvet or felt for a slip fit. Cut slot in one tube, add a guide pin & you can make a crude helical or if you use a threaded cap you could have a helical for cheap.

  4. #14
    Leon Aslan SocalAstro's Avatar
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    Re: Make your own helical focus mount

    Darcy,

    I just took apart an old Vivitar 500mm f/8 mirror lens made for 35mm cameras and it is large enough to house my Nikkor 65mm SW lens, BUT it is too long to build a camera around as it is. I have to reduce it's length to something manageable to allow it to reach infinity focus as others have indicated.

    I may build a second P&S 4x5 or 5x7 camera with this helical, but I'd have to use a longer lens (75mm-90mm).

    Cheers,
    Leon

  5. #15
    come to the dark s(l)ide..... Carsten Wolff's Avatar
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    Re: Make your own helical focus mount

    sorry, late piping in here...
    A problem to be aware of if going down that route: With a lot of the [cheaper] helical options is that the lens will rotate, which ain't much fun, as the cable release and the aperture/shutter speed scales invariably end up in the most awkward positions, not even talking about attempts to add a flashsync cord......hilarious. So consider a proper non-rotating helix.
    http://www.jeffbridges.com/perception.html "Whether you think you can, or think you can't, you are right."

  6. #16

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    Dec 2003
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    Re: Make your own helical focus mount

    I just got a MAMIYA SEKOR 90mm LENS for a MAMIYA 23 got the helical focus mount
    and lens all for $60.00 works great but don't quit do a 4x5 SO I thank I will put in my
    90mm S-K Super Angulon in it as it is a #0 shutter any way
    banjo

  7. #17

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    Dec 2003
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    Re: Make your own helical focus mount

    hey all
    I have been working on my Century Graphic 2x3
    what was trying to do was get a helical focus mount
    to put a Super-Angulon 5.6/47mm maybe Super-Angulon 5.6/65mm
    or a Angulon 6.8/65mm ! the Super-Angulon 5.6/65mm has a #0
    shutter that why I got the MAMIYA SEKOR 90mm LENS for a
    MAMIYA 23 got the helical focus mount is it has a #0 shutter
    But it to big to put on a 23 Century ! so now I have a Kodak Retina Ia
    Rangefinder w/ Zenar f3.5/50mm Lens parts camera coming to
    use the helical focus part of it on my Century . the Retina Ia has a #00
    shutter so I can put my Angulon 6.8/65mm shutter & lens on it Or keep
    looking for a good buy on a Super-Angulon 5.6/47mm as it is also uses
    a #00 so it should work TOO you may ask why I am doing this that to
    use a 47mm on the Century is hard to use the focus is hard to do with
    the bed in the down position with the helical focus mount I can put the bed
    in the down position out of view of the lens & still focus the lens
    so I will maybe use the MAMIYA SEKOR 90mm LENS for a MAMIYA
    23 got the helical focus mount some day BUT for what Darcy Cote
    is trying to do a Mamiya 23 got the helical focus mount mite work for
    him as some the cost is not that bad

    banjo

  8. #18
    8x10, 5x7, 4x5, et al Leigh's Avatar
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    Re: Make your own helical focus mount

    I have a number of new (NOS) zoom lens helical focus assemblies, cheap.

    If you're interested I'll check the diameters. They're pretty large.

    - Leigh

  9. #19

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    Re: Make your own helical focus mount

    leigh, I for one would be very interested

  10. #20
    hacker extraordinaire
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    Re: Make your own helical focus mount

    I made a helical mount for my cigar box camera using an old JC Penny 35mm SLR lens. It fits my 90mm Angulon easily and focuses down to 5 feet.
    Science is what we understand well enough to explain to a computer. Art is everything else we do.
    --A=B by Petkovšek et. al.

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