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  1. #11

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    Quote Originally Posted by pgomena
    The diffraction inherent in pinhole images

    Peter Gomena
    Do you mean diffusion? But yes, on second thoughts, there should be something in it if several people report it. I have seen instructions for making pinhole cameras advocating additional walls inside the camera to reduce stray light. However, my own experience is that it is wise to take care that the shadows receive enough exposure, and if they do, in many motives the highlights tend to become quite dense. In addition, there is the light fall-off in the periphery. Such variables should also depend, at least partly, apart from camera construction on preferred motives and image widths.

  2. #12
    Donald Qualls's Avatar
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    I don't think it's either diffraction or diffusion that's causing the low contrast commonly seen in pinhole images. Rather, it's flare -- specifically, what large format photographers call "bellows flare", caused when a lens with too large an image circle is used; bright light then scatters from the inside of the bellows (or lens cone, or camera chamber) and produces an overall fog on the film that reduces contrast.

    As I said before, I have one camera that doesn't do it at all (i.e. produces images of about normal contrast for the film and development), which I believe is due to a hyper-efficient internal baffle and de facto lens shade resulting from the conversion of the lens to pinhole. Additionally, my AutoPin Polaroid 210 shows very little flare and thus good contrast (with prints for which I have little or no contrast control), probably (I think) because the folds of the bellows capture more light than they scatter. By contrast, a couple of my other cameras that were originally made with lenses that barely covered the format, and converted to the ultra-wide coverage of a pinhole, give pretty normal contrast in controlled light, but flare terribly with a bright sky even just outside the frame.

    Light fall-off can be an issue, but doesn't really affect perceived contrast, which isn't really the full-frame brightness ratio but rather on a scale just above the micro-contrast that influences perceived sharpness. In addition, reduced perceived sharpness tends to reduce the perceived contrast as well -- scenes with the same brightness range will look less contrasty if slightly fuzzy than if perfectly sharp.
    Photography has always fascinated me -- as a child, simply for the magic of capturing an image onto glossy paper with a little box, but as an adult because of the unique juxtaposition of science and art -- the physics of optics, the mechanics of the camera, the chemistry of film and developer, alongside the art in seeing, composing, exposing, processing and printing.

  3. #13

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    Good points, Donald. Diffraction certainly will cause "fuzziness", and a fuzzier image will look less contrasty than a sharp one, and flare will kill contrast. Thinking back to my various pinhole contraptions, the more flare present at the time of exposure, the lower the contrast of the images. On occasions where I was shooting in overcast conditions with the sky to my back, my pinhole images were contrastier. A lens shade apparently is important even if there is no lens present, and internal baffling will help reduce flare. I found that images I made in a high-contrast situation with an old clamshell 5x7 camera produced the grainiest pinhole images I've made yet. Now I have an idea why -- Lots of light bouncing around inside.

    Peter Gomena

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