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  1. #11

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    Quote Originally Posted by Tom Miller View Post
    Try electron microscope slides for apertures. They are precision holes in thin metal. If you buy direct from the manufacturer, they're about $25 for a vial of 100. I have twenty of them on one camera, and have seventy or eighty other single-shot cameras with electron microscope slide apertures. They're fantastic, especially when a bunch of cameras need to act the same and not be subject to the variability of hand-made pinholes.

    Earl Johnson sells them mounted for $1 each plus S & H.
    http://www.f295.org/Pinholeforum/for...?m-1283887930/
    Your URL is broken (or the forum site is having problems), but that could be a very interesting source. I will research further.

    I just wonder how much a stainless steel laser drilled pinhole vs. a soda can & sandpaper hole makes a difference with apertures above 1mm.
    I'm not looking for a sharp image, I just need enough resolution to capture some details in my subject.
    I wondered why there are so many wide angle and so few narrow angle pinhole cameras out there!

    Regarding the COC/FOV factor, it would be very useful to be able to predict the resolution of an image.
    Can I say, as a general rule, that the COC is dependent only on the pinhole size, regardless of the distance from the film (leaving diffraction effects aside) - or is there some relationship with distance too?
    SoFiET
    lii.cc

  2. #12
    andrew.roos's Avatar
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    Excluding diffraction, the CoC for a subject at infinity is the same size as the pinhole.

    The reason for this is simple. For a subject at infinity, all light rays from a point on the subject are parallel. The rays that pass through the pinhole keep on going without converging or diverging (because they are parallel) until they hit the film. So they area they expose on the film is the same size and shape as the pinhole.
    Last edited by andrew.roos; 04-28-2012 at 11:09 AM. Click to view previous post history.

  3. #13

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    Quote Originally Posted by gattu marrudu View Post
    Your URL is broken (or the forum site is having problems), but that could be a very interesting source. I will research further.
    Gattu, I apologize. The link works if you are a member of f295. I think there may now a cost to get access to the
    f295 website. Send me a private message.

  4. #14

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    If you can't get into f295... here's Earl's email address.
    earl.johnson@theobscurecamera.com

  5. #15
    RalphLambrecht's Avatar
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    what is your focallength,distance between pinhole and film?
    Regards

    Ralph W. Lambrecht
    www.darkroomagic.comrorrlambrec@ymail.com[/URL]
    www.waybeyondmonochrome.com

  6. #16

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    I made three different sets - 150, 200 and 250mm on a 35mm camera (taking the distance between the lens mount and the film into account as well, of course). I am testing on the 250 with a 1.2mm pinhole.
    I got some .001mm stainless steel shim and I'll see if the pictures look a bit sharper with a more precise pinhole.
    SoFiET
    lii.cc

  7. #17
    polyglot's Avatar
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    A 1.2mm hole means you're going to have a resolution no better than 20x30. It's going to be a spectacularly blurry mush.

  8. #18

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    Quote Originally Posted by polyglot View Post
    A 1.2mm hole means you're going to have a resolution no better than 20x30. It's going to be a spectacularly blurry mush.
    "Spectacular" is the right word...

    I shot at 3 different FOV's and compared a detail resized to roughly match in size in all the three pictures (see attached image below). Actually, the one that has the best resolution, with the same exposure (I did not correct the tones in the digital image), is the longest tube (the top frame).

    This is a digital shot of course, shot at 1600. Strangely enough, with a Delta 3200 exposed for the same time and developed at 3200 I keep getting blank frames, even taking the film reciprocity failure into account.

    Click image for larger version. 

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    EDIT - sorry, the last line shouldread 150mm - it's a quick and dirty shot (and of course way underexposed)
    SoFiET
    lii.cc

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