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  1. #1

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    Sharper pinhole image

    I have found that using a pin hole with the camera lens, the image is sharper than with just the pinhole by itself. I do'nt think placement of the pinhole in front or behind the lens is critical. Any one else tried this?

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    Dave Wooten's Avatar
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    Quote Originally Posted by kevin klein View Post
    I have found that using a pin hole with the camera lens, the image is sharper than with just the pinhole by itself. I do'nt think placement of the pinhole in front or behind the lens is critical. Any one else tried this?
    does it increase your angle or maintain the angle of the lens?
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    No longer a "pinhole", now an aperture perhaps.
    Don't sweat the petty things and don't pet the sweaty things! http://rwyoung.wordpress.com

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    Quote Originally Posted by kevin klein View Post
    I have found that using a pin hole with the camera lens, the image is sharper than with just the pinhole by itself. I do'nt think placement of the pinhole in front or behind the lens is critical. Any one else tried this?
    Doesn't it seem more like a lens image with much greater depth of field but softened markedly by the diffraction? That is what I would expect, but no, I've not tried it, so you know more than I do.

    Pinhole images actually can be quite sharp, especially if done with large format with a relatively long draw, and then reduced. Also, the quality of the pinhole is a major factor. There are "better" and "worse" pinholes, depending, of course, on what your expected results are.

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    The angle is the same with or without the pinhole,at least in my experiments. I used a 4x5 and tried short and long draws on the bellows,it is much better with the lens. It is'nt pure pinhole photography but I am looking for extreme depth of field for closeup model photography(as in miniatures) for the best realisim.

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    Quote Originally Posted by kevin klein View Post
    The angle is the same with or without the pinhole,at least in my experiments. I used a 4x5 and tried short and long draws on the bellows,it is much better with the lens. It is'nt pure pinhole photography but I am looking for extreme depth of field for closeup model photography(as in miniatures) for the best realisim.
    So, if you are using a 4x5 and that's what you want to achieve, I suspect you'd have better results if you would unscrew one of the elements of the lens and put a black paper disk in there with a small aperture in it, or you might be better with some other material because I suspect that a precise hole would be difficult to make in paper. It would then be at the plane where the aperture is designed to be. I would think that placing it either in front of, or behind the lens would introduce additional anomalies, which, if you are looking for a faithful representation of your subject, could only interfere with the quality you can achieve. The image will be degraded enough through the introduction of the additional diffraction.

    Using the lens in this project as you are doing is far better than pinhole would be. The pinhole used close up brings in a very odd effect where objects closer to the pinhole than the pinhole is to the film become progressively softer the closer they get.

    But, another thought. Using large film with a long pinhole would work well, especially if the film were very oversized and you would reduce it for your final image. Since the dimension of the pinhole is a square function, great advantage is possible in sharpness as the length is increased if the image is to be reduced subsequently. Proportionally to the size of the image, the resolution becomes much sharper. See Alfred Blaker's _Field Photography_ for an explanation of how this works. Seems to me it could be useful for your purposes if you don't mind really long exposure times.

  7. #7

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    I placed the pinhole behind the lens, also tried seperate exposures with only the front element and rear element and pinhole, they turned out blurry. The next experiment is to make a waterhouse pinhole stop and use that in a petzval lens. In the past I had placed the pinhole in front of the lens with equaly good results. The pinhole is simply a piece of aluminum from a pop can and the hole drilled the usual way.

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    Quote Originally Posted by kevin klein View Post
    I placed the pinhole behind the lens, also tried seperate exposures with only the front element and rear element and pinhole, they turned out blurry. The next experiment is to make a waterhouse pinhole stop and use that in a petzval lens. In the past I had placed the pinhole in front of the lens with equaly good results. The pinhole is simply a piece of aluminum from a pop can and the hole drilled the usual way.
    Using a single element or group rather than the whole lens is not likely to work unless the lens is designed for that, such as the symmetrical anastigmats such as the protar, dagor, symmar types. With those, the focal length will be about double that of both groups used together.

    You can use your regular lens instead of the petzval type with the waterhouse stop. It is the same principle.

    If you want quality, I doubt you are going to get much with the aluminum. Aluminum has rather poor working characteristics; brittle, generally produces ragged edges. It works well for people using pinhole to achieve "pinholy" effects, but it doesn't sound like that is what you are looking for. Copper would probably work a lot better for you. Poking a hole with a needle and sanding off the backside with 600 grit sandpaper on a firm block will give a much cleaner hole and a cleaner image, too. Copper is better than brass for similar reasons; it has better working characteristics and can be annealed by heating if you need to rework. You can get .003 inch or so copper shimstock at some auto parts houses. You can blacken the copper in selenium toner, or in livers of sulphur (sodium or potassium sulfide). Easy. Blackening will help keep the lens flare down and will improve your image markedly.

  9. #9
    Dave Wooten's Avatar
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    angle ? doesnt a pin hole lens have a much wider circle at any given focal length than a solid lens? I thought pinhole correctly drilled for optimum would "cover" about 3.5 x's focal length? Think I read it in the Renner.

    Might be possible to "sharpen it up a bit" using a red filter with certain film and light source.
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  10. #10

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    Pinholes give images of wide angular field, free from curvilinear distortion and spectral absorption.
    The optimum pinhole diameter may be calculated by multiplying the pinhole to image distance by the wavelength of light used by3.6 and then taking the square root.

    Both the pinhole to image distance and the wavelength of light should be in the same units,
    e.g. if the pinhole to image distance is 100mm and the wavelength of light is 500nm(i.e. 5x10 to the power of-4 mm)
    then you just multiply 5x10 to the power of-4 mm by 100 by 3.6 and then take the square root which gives 0.424 mm

    Although image brightness and resolution are limited advantages are the large depth of field and wide angle of view.

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