Shape of opening for waterhouse stops
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?
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pictures using a 4x5 monorail camera and a very old enlarging lens, which I believe these Waterhouse stops were originally made for.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!
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.
Here's a link to an old 1919 Wollensak catalog page illustrating them on the cameraeccentric.com website.
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.
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.
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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...
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.
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.
"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.
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.
Originally Posted by calceman
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."