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Thread: camera obscura advice

  1. #1

    camera obscura advice

    I'm kicking an idea around in my head -- a project I might I might propose for possible funding by a local program of small arts grants. I wanted to bounce the idea off you all, who might have some words of wisdom to offer, before I get too far with it.

    There's a historic building in town, in a park -- basically a stone tower. It's round, like a silo, maybe 3 stories high and perhaps 15 feet in diameter. As far as I can tell, it's empty, save a central pole that seems to be some sort of structural support for the roof. The building has one door and one window. The window is directly across from the door, and only about 4 feet off the ground.

    I'm sure you can see this coming: I want to turn this building into a pinhole camera. One with a curved film plane. Seeing as the tower is made of thick stone, I figure this would involve only a lot of black plastic around the door and window, with an appropriately sized hole in one of them. (and the picture would divided by a central line, where the column in the tower blocks or at least distorts the light).

    Then I start to think about the logistics of how to "capture" the image projected. The easy way out would be white sheets taped to the wall and a lensed camera to take a picture of the picture. That may well be the way to go. It would have the advantages of ease, instant feedback (w/digital) and of being color, if there is perceptible color.

    But wouldn't it be more exciting to make an image directly onto a paper positive of some sort? What are the possibilities? Would hand-coating paper or cloth with liquid emulsion be a good idea? (I've heard the Maco brand is very good, but haven't tried it). How would I develop something extremely large? Tiling together lots of pieces of large BW photo paper? What are other options? How did they do it in the airplane hanger?

    An only tangentially-related question: are any alt-process "emulsions" light-sensitive enough to capture the image in a pinhole camera (i.e. cyanotype or platinum or...)? Or would that not work because those processes create images from where the light is fully and partially "blocked" but an image is created in a camera or pinhole camera captures the degree of light everywhere, none of it blocked? Would it work, for example with cyanotype of Van Dyke if the exposure were days long? Does that even make sense?

    Any answers, speculations, discouragements or encouragements much appreciated!

  2. #2

    camera obscura advice

    Cordelia, this is an interesting project. I've built a 'mega' format box camera, 24"x30" format, using a 3x3 grid of 8"x10" sheets of photo paper, taped together in the camera. Post exposure I develop each sheet individually in small trays, then contact print them. The resulting prints can then be reassembled into the grid-like composite image.

    B/W photo paper is sensitive enough to capture brightly lit daylight scenes; using the above method you can also use panchromatic sheet film, and get much quicker exposure times; although you would have to work in complete darkness to set up the sheets and take them down. With paper negatives you could work under dim red light safely.

    Alternative process emulsions like cyanotype are way too slow for pinhole; I've exposed some in glass-lensed cameras and they're still way too slow for practical photography. Liquid silver gelatin emulsions give you essentially the same type of sensitivity and commercially made B/W paper negatives, but you have the added fun of sizing and coating your chosen surface. No real advantage other than you can choose a surface other than paper.

    There are also mural-sized rolls of B/W photo paper, available from places like Freestyle; you could transport one of these rolls in a light-safe container; set it up in the camera obscura; make your exposure; then transport it back home to where you can use plastic painters troughs within which to "dip and dunk" process the paper mural.

    For color images by far the easiest method is to photograph the projected image using another camera.


  3. #3

    camera obscura advice

    If you search for Abe (Abelardo) Morell's work, his camera obscura room photos are/were (generally, since I don't know everything he's done) shot with a view camera inside the camera unknown to me, but exposures on b/w panchro film (with a lens) as long as 8 hours.

    Camera Obscura image brightness I imagine to be pretty low...the one time I set one up (3 days with an aperture only, last day with a lens (4000 mm f/100 (= +0.25 diopter, 40 mm diam))), it was interesting to observe how different people adjusted to vision in the dark. One woman asked if pinhole images were all b/w...while standing inside the camera obscura with the rest of us. I realized it was 'night vision/color sensitivity' issue prompting the question, so I didn't get to enjoy a laugh at the question.

    It took a while for her to believe we could see color in the image, but after a couple more minutes and identifying bright objects with known colors (a flag in the sun), she was 'on board' with us, more or less.

    Jim Jones (member here) recommended a double layer of 0.006" black plastic sheet. We had alot of windows to cover. I ended up using a single layer for mechanical issues, and there were no pinhole leaks...maybe the second time they try to reuse the plastic that may not be true!

    The biggest problem was light coming in at the bottom of the windows where there was a ledge making the plastic not lie where we wanted it.


  4. #4

    camera obscura advice

    Murray + Joe --

    I'm reasonably familiar with and quite inspired by Abelardo Morrell's work. He actually lives and teaches at the art college in Boston (where I live) though I've never had the pleasure of meeting him. There's actually an absolutely terrific documentary about him, his work and about being a Cuban-American. It's called "In the Shadow of the House" and I'd strongly recommend it to all photographers -- and non-photographers. An extremely interesting film all-round... a lot of insight into how he works, too. I'm not sure of its availability (I saw it at the Boston Independent Film Festival last year or the year before), but keep an eye out.

    I expect the most REASONABLE thing for me to do would be to photograph the camera obscura image with a lensed camera. Maybe various different lensed cameras. (That could be cool... the same image shot with digital, medium format, plastic cameras, etc. and made into some sort of diptych/triptych, whatever).

    I expect the logistics of getting into and blacking out this tower (working with the public works department and so forth) would probably be enough complications for my first project of this sort -- then I can move on to fancier techniques in future, after I see how this works. I don't have my own darkroom, so arranging a place to process huge swaths of paper would just add to the complications. (though I love the idea of doing a mural with paper from Freestyle or wherever -- of course that would exist, why didn't I think of that?) Maybe that will be next.

    I'm sure I could find this info with a little digging, but what is the "speed" rating of chemicals like cyanotype? I feel like I learned at some point that your average BW RC photo paper is about a 4 ASA. Does that make cyanotype something like .5? Less? What about processes like albumen, where the image gets exposed much quicker in UV light than cyan or VDB? Just curious...

    THanks for the ideas! More always appreciated.

    - Annie (aka Cordelia)

  5. #5

    camera obscura advice

    Another large pinhole project is at

  6. #6

    camera obscura advice

    Quote Originally Posted by 1198
    Another large pinhole project is at
    the largest pinhole i have ever seen can be found on this site:

    he converted a contractor's shed to a pinhole camera ;-)


  7. #7

    camera obscura advice

    1) I really don't know, but suspect cyano and other deep blue to UV-sensitive processes are alot slower than any paper or graphic arts film...I can't cite anything specific off-hand, but got a gut feeling it's more than 'alot' slower, like maybe many times slower. I think the traditional alt-process recipes are (generally considered) too slow for in-camera use, even with a 'normal' f-stop/lens.

    You might look at Mike Ware's modified processes to see if one of the 'newer' formulae is fast enough for in-camera use...I think I read someone accomplishing that...or at least theorizing...maybe ImageMaker (pretty scarce here lately), a.k.a Donald Qualls on APUG, etc.

    2) Re: "Shadow of the House"... I missed it at a local Hispanic festival, and called to ask about renting that time it only had educational licensing at $400, but they told me a time frame (either late 2007 or 2008, I forgot) when it would be available at your local video rental store.

    I see it is available as a DVD purchase now (NTSC only) for US$35

    Rental I will ask about, now that I know it exists...maybe local public library!


  8. #8

    camera obscura advice


    I once tried exposing cyanotype paper in an F/3 lens camera (need I mention that F/3 is a heckuva lot faster than the typical pinhole camera); after several HOURS of exposure IN BRIGHT SUN, there was barely any visible image.

    So, it's roughly 6 stops more exposure time required for an F/190 pinhole vs an F/3 lens (6,12,24,48,96,192). That's doubling my "several HOURS" of exposure 6 times over. Say, optimistically, 2 hours for a base exposure of F/3 that BARELY registers any density; doubled 6 times is 4,8,16,32,64,128 hours of exposure. That's 128 hours, assuming there's no reciprocity failure with cyanotype. Now, this was with "Sunprint" brand commercial cyano paper, developed straight off in water; you may get a tad more speed, as Murray mentioned, using a newer cyano formula. But I doubt if you would get enough additional speed to make a considerable difference. That's not to say you shouldn't try it; perhaps it might work. I'd like to see your results.


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