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  1. #21
    baachitraka's Avatar
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    I do not know whether this is related to this discussion.

    I am wondering why bellows in LF having ridges rather than smooth taper. Curious to know, how light propagates through the ridges.


    Quote Originally Posted by markbarendt View Post
    Had another thought here.

    It isn't that you can see sharper, squinting actually degrades sharpness and clarity.

    What it does do though is simplify the image, because extraneous detail is no longer "distracting" us, the "essence" remains/becomes more clear, not the image itself.
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  2. #22
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    Quote Originally Posted by baachitraka View Post
    I do not know whether this is related to this discussion.

    I am wondering why bellows in LF having ridges rather than smooth taper. Curious to know, how light propagates through the ridges.
    There is normally no interference from the ridges, they are normally outside the path the light follows from lens to film.

    Now if the bellows is allowed to sag into the light path then it will simply block the light in that area, nothing reaches the film.

    There is no difference in this effect for a non-ridged, bag, bellows.
    Mark Barendt, Ignacio, CO

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  3. #23
    David Brown's Avatar
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    Quote Originally Posted by baachitraka View Post
    Will adding an another aperture to an existing lens produces any sharper pictures, provided both apertures have same or different opening?
    Probably not.
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  4. #24
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    Quote Originally Posted by baachitraka View Post
    I do not know whether this is related to this discussion.

    I am wondering why bellows in LF having ridges rather than smooth taper. Curious to know, how light propagates through the ridges.
    The ridges and folds allow the bellows to compress and expand for focusing, and are structural so the bellows will not sag (much) when extended. They also allow a camera to fold up for transport. The bellows are black on the inside to reduce reflections, and larger than the image cone coming out of the lens so no light is propagated through them, and virtually no light is reflected off of them inside the camera.
    Last edited by rjbuzzclick; 06-22-2011 at 02:42 PM. Click to view previous post history.
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  5. #25
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    Quote Originally Posted by baachitraka View Post
    As you might have experienced that squinting human eye can able to see outside world slightly sharper...

    With that, Will adding an another aperture to an existing lens produces any sharper pictures, provided both apertures have same or different opening?

    Just curious...
    Probably not. Apertures are usually placed at the nodal point of the lens. There is only one of those. An aperture placed in a different spot either won't have an effect or will become the de facto aperture, but in the wrong place. There are however many "tricks" available in optics, but in the end it's all math and physics, and there is rarely a free lunch with those two.

  6. #26
    baachitraka's Avatar
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    One of the inspiration to ask about two apertures is that I use to work with corrugated horn antennas with different profiles.

    http://www.google.com/search?um=1&hl...34l769l2.1.2l5

    The mathematics behind is quite complicated. I just wonder whether it is possible to shape the light waves through two more apertures...

    Quote Originally Posted by JBrunner View Post
    Probably not. Apertures are usually placed at the nodal point of the lens. There is only one of those. An aperture placed in a different spot either won't have an effect or will become the de facto aperture, but in the wrong place. There are however many "tricks" available in optics, but in the end it's all math and physics, and there is rarely a free lunch with those two.
    OM-1n: Do I need to own a Leica?
    Rolleicord Va: Humble.
    Agfa Isolette III: Amazingly simple, yet it produces outstanding negatives.
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  7. #27
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    Quote Originally Posted by markbarendt View Post
    The Sony lens is a soft focus lens, not a super sharp lens.
    Sorry, but that's just not true. The STF is not a soft focus lens, it does not have deliberate spherical aberration, in fact it has remarkably low SA and is one of the very sharpest 135mm lenses you will find. It introduces no softness (reduction in resolution) to any part of the image, either in-focus or out-. It was originally a Minolta AF lens and Sony continues to make it, so it (including the current Sony version) will work with any Alpha/Dynax/Maxxum 35mm cameras people might have.

    What it does is have an apodisation filter (dark at the edges, light in the middle) very close to the aperture. This means that when shot wide open, the bokeh has a gaussian rather than circular form, which means that you no longer have blur circles with sharp edges but big soft blobs with no visible edge whatsoever, which means that backgrounds become beautifully smooth.

    With any lens (ignoring aberrations), a point source appears on the film as an image of the lens' aperture, scaled by how far out of focus it is. So a focused point is a point, a defocused point will appear as a circle/septagon/whatever with sharp edges. If you then put the apodisation filter next to the aperture, that circle is dimmed at the edges and you lose the sharp edges on your bokeh.

    As to the original poster - your vision gets sharper because when you squint, you're manually stopping down your aperture. The eye is a very simple lens that works poorly wide-open. Our vision is sharp in bright sunlight (small pupils, high f/number) but in dim light, the pupils open up, expose more of the poorer-performing part of the lens and your vision gets softer.

  8. #28
    markbarendt's Avatar
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    Dang, wrong again.
    Mark Barendt, Ignacio, CO

    "We do not see things the way they are. We see things the way we are." Anaïs Nin

  9. #29
    baachitraka's Avatar
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    Thanks for clarification, further STF has two apertures.

    Quote Originally Posted by polyglot View Post
    Sorry, but that's just not true. The STF is not a soft focus lens, it does not have deliberate spherical aberration, in fact it has remarkably low SA and is one of the very sharpest 135mm lenses you will find. It introduces no softness (reduction in resolution) to any part of the image, either in-focus or out-. It was originally a Minolta AF lens and Sony continues to make it, so it (including the current Sony version) will work with any Alpha/Dynax/Maxxum 35mm cameras people might have.

    What it does is have an apodisation filter (dark at the edges, light in the middle) very close to the aperture. This means that when shot wide open, the bokeh has a gaussian rather than circular form, which means that you no longer have blur circles with sharp edges but big soft blobs with no visible edge whatsoever, which means that backgrounds become beautifully smooth.

    With any lens (ignoring aberrations), a point source appears on the film as an image of the lens' aperture, scaled by how far out of focus it is. So a focused point is a point, a defocused point will appear as a circle/septagon/whatever with sharp edges. If you then put the apodisation filter next to the aperture, that circle is dimmed at the edges and you lose the sharp edges on your bokeh.

    As to the original poster - your vision gets sharper because when you squint, you're manually stopping down your aperture. The eye is a very simple lens that works poorly wide-open. Our vision is sharp in bright sunlight (small pupils, high f/number) but in dim light, the pupils open up, expose more of the poorer-performing part of the lens and your vision gets softer.
    OM-1n: Do I need to own a Leica?
    Rolleicord Va: Humble.
    Agfa Isolette III: Amazingly simple, yet it produces outstanding negatives.
    Holga 120GFN: EV 11 or EV 12.

  10. #30
    Steve Smith's Avatar
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    If you want sharp focus and minimal depth of field at all aperture settings then you need to fit a variable aperture in the same shape as a cat's eye. i.e (). No matter how closed up it is, the image is formed from the full diameter of the lens.


    Steve.

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