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  1. #11
    Paul Cocklin's Avatar
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    oh, pics look really good, too. Very cool looking camera.

  2. #12
    SMBooth's Avatar
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    Quote Originally Posted by Paul Cocklin View Post
    Just curious, how would one calculate coverage of image circle? I've been thinking of doing a 4x5 pinhole camera myself, (and will, eventually) and was wondering how far back the holder needs to be to ensure full coverage. Also, I know that it's said that these types of cameras have infinite dof, (or lack thereof) but is there an actual hyperfocal distance?
    Try this link http://www.mrpinhole.com/index.php

  3. #13
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    Well, in the Windoze environment, there is Pinhole Designer which has all sorts of handy calculations. I think in theory the field of view approaches 180º, but the light falls off and, as seen in CuS' photo on Flickr, the ultimate coverage can wind up being limited by the mechanics surrounding the pinhole. My first body cap adapter for the Bronica suffered serious vignetting, after which I did what I should have done in the first place and plotted a scale drawing of all the parts and spacings to work out larger holes for some of the components. Rev 2 was way better, even though the pinhole and the pinhole-to-film spacing didn't change. As a practical design, I would guess a 90º angle of view (film to pinhole distance approximately equal half the diagonal of the film frame) should be easily possible, and maybe out to 120º or so. But it can get tricky, as even the thickness of a foamcore or plywood mounting board could cause vignetting at some point.

    I believe a knife-edge pinhole is needed for very wide angles too, or at least a very thin foil. Otherwise the light fall-off will be more severe.

    The next step is then to work out an optimum pinhole diameter for the given spacing. Using a press camera was cool because the film-to-pinhole distance could be varied over a large range with one pinhole installed.

    I wouldn't say there's a hyperfocal distance, but there is an interesting phenomenon observed by several of us last year. As you look further into the background, there seems to be softer focus. This is apparently caused by resolution required to render the detail reaching a point where it is greater than the pinhole can render, not really a focus issue.

    DaveT
    Last edited by DWThomas; 06-22-2009 at 09:30 PM. Click to view previous post history.

  4. #14
    Paul Cocklin's Avatar
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    Thanks to both of you for the info. I appreciate the details, Dave. Sorry to the OP for taking a detour with his thread.

  5. #15
    AlternativePhotograp's Avatar
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    Hi Paul, and everyone else.
    The image circle is roughly 3,5 times the focal length. There is a book i have just co-written which covers the basics of pinholing, this and a lot more. It's called "From pinhole to print - in less than an hour" More info here:
    http://www.alternativephotography.co..._to_print.html
    Good luck!

  6. #16
    CuS
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    Quote Originally Posted by Paul Cocklin View Post
    Just curious, how would one calculate coverage of image circle? I've been thinking of doing a 4x5 pinhole camera myself, (and will, eventually) and was wondering how far back the holder needs to be to ensure full coverage. Also, I know that it's said that these types of cameras have infinite dof, (or lack thereof) but is there an actual hyperfocal distance?

    I was using this formula which related pinhole diameter to focal length:

    d=(sqrt(f))/25

    where:
    d= pinhole diameter
    f=focal length

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