Shape of opening for waterhouse stops

Discussion in 'Large Format Cameras and Accessories' started by calceman, Aug 29, 2009.

  1. calceman

    calceman Member

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    In the book "vie camera techniques" by Leslie Stroebel (p110, figure 5.34), there's a mention of out of focus images in bright lights produce in focus images of diaphragm opening (I suppose it could be bohke).
    I have an old barrel lens with no diaphragm, so I will make some waterhouse stops sometimes soon. Instead of making them as a perfect circle, I am thinking of cuting the hole as other geometries (stars, heart, moon crescent...) for experimental bohke. This may influence sharpness, but I contact print 8x10, so its not so important.
    Anybody tried this? Any thoughts of possible results?
     
  2. Mick Fagan

    Mick Fagan Subscriber

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    I have a set of Waterhouse stops, 6 in all I think, they are all square openings.

    The square openings certainly make a difference. They were used for some advertising pictures using a 4x5 monorail camera and a very old enlarging lens, which I believe these Waterhouse stops were originally made for.

    Along the way the enlarging lens went missing when we moved our business to bigger, larger and brighter premises in the late eighties. I was given the Waterhouse stops, mainly because I could possibly use them on my German manufactured Berthold reprographic camera and the single peculiar lens I had for it at the time.

    Yes, interesting picture on page 110.

    However the picture on page 143, 6-35, has fascinated me ever since purchasing this book, Gestalt organisational law of continuation, what a name!

    Mick.
     
  3. smieglitz

    smieglitz Member

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    Here's a set of original stops for a Wollensak Verito lens. I have not used them since my Veritos are not the right size for these, but have always been curious about their effect.

    [​IMG]

    Here's a link to an old 1919 Wollensak catalog page illustrating them on the cameraeccentric.com website.

    Joe
     
  4. calceman

    calceman Member

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    Beautiful stops, but maybe to diffucult of a pattern to reproduce at home... As far as I understand, the more branches for a star, the larger the amount of diffusion. Probably similar to the imagon with its perforated "waterhouse" accessories.
    So maybe, best to keep the shape not too far from a circle (square, heart or whatever else). Mick, what's the effect of a square opening?
    ***off topic''' For the Gestalt organisational law of continuation, you can always check "transparant screens" on flickr.
     
  5. Mick Fagan

    Mick Fagan Subscriber

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    The square opening on the camera, was more pronounced than on an enlarger.

    The effect is four areas, as in the four corners of the stop, being virtually the same as a wide open lens, whilst the centre of the squares, so to speak, was more in focus, or appeared to be more in focus.

    There was also a vignetting effect in the four corners when used on the enlarger, that is the corners of the square stop got slightly more light than the centre of the squares. This combined with the slight differences of sharp focus, made for a neat effect.

    Another thing was the ability to expose the negative with a square stop in alignment with the negative edges, then when enlarging, rotate the film to whatever angle will give the most desired effect.

    The best enlarger for this type of work was our Beseler 4x5 with the rotating neg stage carrier.

    Mick.
     
  6. calceman

    calceman Member

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    I'd like to know if, when used wide open, you get bohke that has squares instead of circles.
    So anything that spills out of a circle will increase diffusion. But wide open, do you register the shape of the diaphragm opening or not?
    My guess is that I will try out in a couple of weeks...
     
  7. David A. Goldfarb

    David A. Goldfarb Moderator Staff Member Moderator

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    Bokeh refers broadly to the quality of the rendering of the out of focus areas of an image, and not just to the shape of out of focus points of light, but those out of focus points of light will take the shape of the diaphragm.

    As I understand it, diamond shaped stops were used for color separations in the printing industry, and the stop was rotated for different colors when making the halftone screen, but maybe one of the printers here can explain that more clearly.

    Stops like the Imagon's "sink strainer" stops and Joe's star-shaped Verito stops are designed to reduce exposure while retaining some of the spherical aberration that produces the lens's signature diffuse focus effect and would otherwise be reduced by stopping down the lens with a normal iris diaphragm.
     
  8. calceman

    calceman Member

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    Looks like there's some science involved in the shape of the diaphragm, and influence diffusion and even colour separation...
    In the imagon, the main larger opening in the center increases depth of field, but each peripheric hole would allow small amounts of light to hit the film and create faint offset images giving the diffuse effect. Most likely normal lenses with this type of sink strainer type of diaphragm would produce similar soft images.
    Anyway, the shape and amount of holes in waterhouse stops looks like a good thing to experiment with.
     
  9. phfitz

    phfitz Member

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    "Anyway, the shape and amount of holes in waterhouse stops looks like a good thing to experiment with."

    Physical placement of the slot will also change the effect, most are just ahead of the iris, imagon is in front of the lens, Verito was just behind the front lens.

    If you have a filter slip for the lens, you can make ANY shape aperture with aero-duplicating film, ultra clear film base, ultra high D-max.
     

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  10. David A. Goldfarb

    David A. Goldfarb Moderator Staff Member Moderator

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    Not particularly. Most normal lenses are designed to be well corrected for spherical aberration, while an Imagon is designed to "poorly corrected" for spherical aberration to produce the diffuse effect. On a poorly corrected lens, rays entering the lens at the periphery focus at a different plane from rays entering at the center, causing a diffuse image to be superimposed on the sharp image. Normally, this effect would be reduced by stopping down, but the sink strainer or star diaphragm allows those rays from the periphery to reach the film. With a well corrected lens, all the rays focus at or close to the same plane, so allowing more peripheral rays to reach the film would not create much of a diffuse image, because there isn't one there to begin with.

    As an aside, there are subjective considerations involved in what exactly "well corrected" means, since a certain amount of spherical aberration can be aesthetically appealing even in a lens that is intended to be a "sharp" (as opposed to "soft focus") lens, and too much correction is sometimes associated with various kinds of "bad bokeh."
     
  11. numnutz

    numnutz Member

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    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 :smile:
     
  12. calceman

    calceman Member

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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.
     
  13. David A. Goldfarb

    David A. Goldfarb Moderator Staff Member Moderator

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    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.
     
  14. Lee L

    Lee L Member

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    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
     
  15. keithwms

    keithwms Member

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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 :wink:

    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.
     
  16. calceman

    calceman Member

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    David, that particular catalogue is in french, bottom of p27 in the text, not in the figure (http://www.cameraeccentric.com/html/info/emilbusch_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."
     
  17. calceman

    calceman Member

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    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.
     
  18. David A. Goldfarb

    David A. Goldfarb Moderator Staff Member Moderator

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    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.
     
  19. calceman

    calceman Member

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    Which would be the subject of another thread: "in-camera Dodging". :wink:
     
  20. phfitz

    phfitz Member

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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.
     
  21. David A. Goldfarb

    David A. Goldfarb Moderator Staff Member Moderator

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    I thought of a photographic diaphragm, like some people use film to make zone plates, but I wonder if that was a likely way of doing things in 1911. Film was in use, certainly, but I wonder if it had yet become more common for large format photography than dry plates. I've had filmholders dating from that era and earlier, so it was certainly possible.
     
  22. calceman

    calceman Member

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