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Thread: camera obscura

  1. #1

    camera obscura

    I installed a brief (3-4 days) camera obscura locally as an experiment. Initially I started with a variable iris, about 1.25-1.5" in a 33'x24' or so room. 90 degrees away I put in a 4m (13') zoneplate made my a list member (I won't name unless he volunteers, so he doesn't get swamped with requests).

    There was a portable wall, v-shaped with a 90 degree corner in the gallery. For optimal use at the zone plate side, it was in the way of the main aperture. The sun was able to illuminate the zoen plate, so at sunset it looked like a flashlight spot. So we covered it up.

    It became overcast, and I tried a 0.25 diopter (4000 mm) 40 mm diameter (f/100) lens, and despite similar or worse f-number compared to the open iris, the lens brightened and sharpened things in a much better way. I was sure that DOF would be terrible so I didn't try it until the last day. It was actually good.

    I did not want to spend time with a learning curve shooting with film in the dark, so I just set up a digital camera. Phone cam did not have enough sensitivity. I shot 15 seconds @ f/5.6 which was EV1 (I think I was on ISO 100, but didn't check). I had to brighten images in GIMP, so the light level was still lower than EV 1.

    Here are two images.

    The right angle wall was moved in front of the f/100 lens. If you look carefully you can see how the flat building was bent into the 90 degree corner and the 6" thick wall ends are visible.

    An inverted view is also included for convenience.

    Cars, bicycles, runners and a person with a limp were all interesting to watch moving by. A tree in front of the gallery was macro, larger than 1:1.

    Cars seemed to be affected by a 'visual Doppler effect', their speed changing and seemingly moving around the room as the image changed walls. The lens also projects aberrations at the far end of the room.

    It was well received, and they want to do it again this summer during their art camp.

    Attached files

  2. #2

    camera obscura

    inverted for convenience

    Attached files

  3. #3

    camera obscura

    Wow, Murray, that's a great-looking image! The facade has the look of a cardboard cutout.

  4. #4

    camera obscura

    I'm impressed !!!

    moot's right, it looks like a cutout or maybe a folding printed screen

  5. #5

    camera obscura

    I'm impressed !!!

    moot's right, it looks like a cutout or maybe a folding printed screen

  6. #6
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    camera obscura

    This is very cool, Murray. You did a good job.

  7. #7

    camera obscura

    Thanks.

    90 degree wall facing the pinhole (later lens).

    Camera angle distorts further too...I just got as far back as I could which wasn't far enough.

  8. #8

    camera obscura

    Cool images Murray.

    I think you responded to my earlier thread about building camera obscuras. I have written a small grant proposal to build one in a cool local building and do portraits of community members and then create an exhibit. I'm still waiting to hear about that. (I'll probably do it whether I get the grant or not... it was really just a way to facilitate getting the public works department on board... the project isn't going to be expensive, except for framing for the gallery).

    Anyway, I've heard you and others mention diopter lenses in relation to camera obscuras. Are these just the filter-like lens-things that magnify? I have a bunch of them in my box of random filters and lens-bits (from a junk auction) and use them to make weird close-up lens mods sometimes. Or are you talking about something else I don't know about?

    What's rationale of different diopter lenses on a camera obscura (vs. a straight pinhole, for example)?

    Thanks so much, and thanks for sharing the neat stuff!

    annie
    (cordelia)

  9. #9

    camera obscura

    OH! and, I forgot to mention, I too have been bemused watching the neat look of MOVEMENT through camera obscuras... people walking by and so forth... but your post gave me the idea to actually film some of my public camera obscura project to mini-DV (probably in the "night vision mode"!). I can have the film playing at the exhibit too...

    Thanks for sparking good ideas!

  10. #10

    camera obscura

    Quote Originally Posted by 1570
    Cool images Murray.

    What's rationale of different diopter lenses on a camera obscura (vs. a straight pinhole, for example)?

    annie
    (cordelia)
    Annie,
    A diopter lens will bring in a lot more light. Usually it takes a few minutes for your eyes to adjust and see the pinhole camera obscura image. With a diopter you will see an image before the door to the room is closed. This usually make it easier to draw. You do need to get the right diopter for the room. Diopters have a focus point, a +1 focuses at 1 meter, a +2 focuses at 1/2 meter, a +0.5 focuses at 2 meters. I made a tent camera obscura that I sued like you are proposing. I had the friend, artists and the general public draw in my tent then I showed the drawings in a gallery. Here is a link to my tent camera obscura, http://www.pinholeblender.com/co.html

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