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  1. #11

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    Here's a set of original stops for a Wollensak Verito lens
    How would the F Stop value be calculated for these Waterhouse stops. I understand the focal length / effective aperture formula, but what about the additional light transmission from the triangular bits.

    Are there any other interesting soft focus patterns around?


    nn

  2. #12
    calceman's Avatar
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    From the Camera Eccentric catalogue page (Emil Busch 1911), the star-shaped iris is a way of illuminating the periphery of the negative, instead of using the circular ND filters. So many used for wide angle lenses.

  3. #13
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    Quote Originally Posted by calceman View Post
    From the Camera Eccentric catalogue page (Emil Busch 1911), the star-shaped iris is a way of illuminating the periphery of the negative, instead of using the circular ND filters. So many used for wide angle lenses.
    Do you have a direct link for that? It's a large site, and though I found the excerpts from the 1911 Busch catalogue, I didn't turn up any discussion of star shaped irises on a quick skim, and the ultrawide lenses in that catalogue all show perfectly round wheel stops.

    A star shaped iris could be used in this way, if the shape were right, but I suspect it would result in a sacrifice in sharpness, hence the "fan" on the Goerz Hypergon, which was designed to be used for part of the exposure to even out exposure in the corners.
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  4. #14
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    Quote Originally Posted by numnutz View Post
    How would the F Stop value be calculated for these Waterhouse stops. I understand the focal length / effective aperture formula, but what about the additional light transmission from the triangular bits.

    nn
    Calculate the total area of the opening in the waterhouse stop. Then calculate the diameter of a circle with the same area. Divide the focal length of the lens by the circle diameter you calculated and that's your working f-stop.

    Lee

  5. #15
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    I have been making my own waterhouse stops using developed but unexposed scraps from medium format E6 films. They seem opaque enough. I have been cutting holes with scissors, a knife, a razor, hole punch, a drill, whatever. Anything goes. You can make whatever shape you want. Just go nuts and experiment and enjoy making your own 'signature' apertures

    I would suggest looking at the aperture discs for the imagon and the mamiya rb/rz/645 SF lenses. They were probably well thought-out and tested designs, so they might make nice templates. Actually I am currently rigging the discs from a 150 SF in a brass lens. The main issue I had with my E6 film apertures is that they are so thin that they don't stay in place so well, so then you can wind up with an effectively elliptical opening.
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  6. #16
    calceman's Avatar
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    Quote Originally Posted by David A. Goldfarb View Post
    Do you have a direct link for that? It's a large site, and though I found the excerpts from the 1911 Busch catalogue, I didn't turn up any discussion of star shaped irises on a quick skim, and the ultrawide lenses in that catalogue all show perfectly round wheel stops.

    A star shaped iris could be used in this way, if the shape were right, but I suspect it would result in a sacrifice in sharpness, hence the "fan" on the Goerz Hypergon, which was designed to be used for part of the exposure to even out exposure in the corners.

    David, that particular catalogue is in french, bottom of p27 in the text, not in the figure (http://www.cameraeccentric.com/html/...ilbusch_1.html). Roughly, it goes like this:

    "The anastigmat pantoscope is a wide angle lens for extreme situations; but when using all the image, the luminosity around the borders will inevitably dicrease so that the photographer will have to rely on mechanical tricks (by moving the lens cap in front of the lens, or with a star-shaped iris that you could cut out yourself), or partially re-inforcing the borders of the plate."

  7. #17
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    Quote Originally Posted by keithwms View Post
    I have been making my own waterhouse stops using developed but unexposed scraps from medium format E6 films. They seem opaque enough. I have been cutting holes with scissors, a knife, a razor, hole punch, a drill, whatever. Anything goes. You can make whatever shape you want. Just go nuts and experiment and enjoy making your own 'signature' apertures

    I would suggest looking at the aperture discs for the imagon and the mamiya rb/rz/645 SF lenses. They were probably well thought-out and tested designs, so they might make nice templates. Actually I am currently rigging the discs from a 150 SF in a brass lens. The main issue I had with my E6 film apertures is that they are so thin that they don't stay in place so well, so then you can wind up with an effectively elliptical opening.
    For waterhouse stops, I used dark slide from some run down holder. It is a too brittle, but managed to drill holes.
    Now I found a black plastic satchel that is now being cut-up. These stops are great, bendable, and easy to "drill" by turning scissors and sand paper at the end.

  8. #18
    David A. Goldfarb's Avatar
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    Quote Originally Posted by calceman View Post
    David, that particular catalogue is in french, bottom of p27 in the text, not in the figure (http://www.cameraeccentric.com/html/...ilbusch_1.html). Roughly, it goes like this:

    "The anastigmat pantoscope is a wide angle lens for extreme situations; but when using all the image, the luminosity around the borders will inevitably dicrease so that the photographer will have to rely on mechanical tricks (by moving the lens cap in front of the lens, or with a star-shaped iris that you could cut out yourself), or partially re-inforcing the borders of the plate."
    Thanks. I missed that. I wonder, though, how practical this would be, since such lenses are designed to be used around f:22-45, and cutting a tiny star-shaped diaphragm of the appropriate shape and size very precisely would not be so easy for any but the largest Pantoscope lenses. It would make more sense to make a star shaped dodging tool and wave it in front of the lens for part of the exposure.
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  9. #19
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    Quote Originally Posted by David A. Goldfarb View Post
    It would make more sense to make a star shaped dodging tool and wave it in front of the lens for part of the exposure.
    Which would be the subject of another thread: "in-camera Dodging".

  10. #20

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    "I wonder, though, how practical this would be, since such lenses are designed to be used around f:22-45, and cutting a tiny star-shaped diaphragm of the appropriate shape and size very precisely would not be so easy for any but the largest Pantoscope lenses."

    Photograph it to size. Aero-duplicating film and Shanghai B&W 100 have ultra clear base/fog levels and should work well. E6 could work but may have a color cast to it. You can also choose to use a star or inverse star or any pattern that you can doodle with a Sharpie.

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