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  1. #11
    Vlad Soare's Avatar
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    I still do not know what is diamagnetism
    Diamagnetism is the tendency of some non-magnetic materials to be very slightly repelled by strong external magnetic fields.

    Tape recorder heads detect the variations in the magnetic field of the tape. Silver, being non-magnetic, has no magnetic field, so there's nothing that an ordinary tape recorder head could detect.
    You'd have to place the film in a strong magnetic field and to devise some means of measuring how strongly different areas of the film respond to it. It sounds interesting, but I have no idea how (and if) it could be done. Physics isn't my forte.

  2. #12
    Worker 11811's Avatar
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    There are three basic magnetic properties of materials: Ferromagnetic (magnetic) -- Paramagnetic. -- Diamagnetic (anti-magnetic)

    Materials such as iron, cobalt, neodymium or nickel are ferromagnetic. The electrons in their atoms are arranged in such a way that they can be magnetized and will retain said magnetization under certain conditions, even outside the presence of other magnetic fields.

    Materials like tungsten, cesium, aluminum and magnesium are paramagnetic. They will become temporary magnets but only in the presence of a (relatively) strong magnetic field. As soon as the external magnetic field is removed, they will return to their non-magnetic state.

    Silver, copper and many other materials are diamagnetic. Not only are then non-magnetic, they are actually repelled by magnetic fields. If you put them in a strong enough magnetic field, it is possible to make small amounts of these materials levitate due to this repulsion.

    Even though silver isn't magnetic, you might be able to detect an eddy current around it. Place it in a strong, alternating field and you can induce a field around it which can be detected with a second coil of wire. Metal detectors such as the ones you see in airports or like you see men using on the beach to find lost coins operate on the eddy current principle.

    There are two coils of wire inside the detector head. One is the "exciter" coil. The other is the "sense" coil. The exciter has a fairly strong electric current going through it. This current causes an electromagnetic field to develop around the coil. Any metal which comes near the exciter coil will be induced to have its own temporary magnetic field. The sense coil is also induced to have a magnetic field but, when the metal comes near, the field in the sense coil will be partially or completely stifled due to the field around the detected object. The metal detector's electronics will sound the alarm when the sense field is interrupted.

    It is possible to tell how much metal or what kind of metal is inside the detection field based on the strength of the response. Larger metal objects react more strongly. More distant objects do not react as strongly. Further, different types of metal exhibit unique characteristics inside the field. The induced field develops faster or collapses at different rates, depending on the type of metal. This is why security guards at airports are alerted when a person has a large amount of metal but not if there is merely a coin in his pocket. (The can set the sensitivity of the machine.) This is also how those coin finders on the beach can tell the difference between silver, copper and other metals. They detect the profile of the alternating field as it expands and collapses around the object.

    So, no, you can not record information on a piece of silver-impregnated film but it MIGHT be possible to use eddy current detection to read information.

    I am only supposing... It MIGHT be possible to "burn" a series of black and white stripes, similar to a bar code, on a strip of film and pass it through an eddy current detector. The alternating silver/clear patches on the film should be detectable. You'll have to experiment to see what you can do with this idea. I'm not sure how it will work. As I said, I'm just guessing.
    Randy S.

    In girum imus nocte et consumimur igni.

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    http://www.flickr.com/photos/randystankey/

  3. #13
    holmburgers's Avatar
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    Umut,

    You should study how old video worked, Like Quad 2... http://en.wikipedia.org/wiki/2%22_Quadruplex_videotape

    And yes tape recorders still exist, and I use them to record in my band; you can get new tape from Quantegy.

    Perhaps one of the other "non-silver" photography methods utilize a substance that is ferromagnetic?

  4. #14

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    Quote Originally Posted by Mustafa Umut Sarac View Post
    I invite you to write whatever you think about problems and advantages. Slower the scan or bigger the recording surface , you get more resolution , I guess.

    Thank you,

    Umut
    Then read what is said above. It was told and said already before you wrote that.

    The resolution problem is not a matter of speed, but of how big the magnetic 'units' that might (if they could, or would) record info are , and how small the units are a head can resolve.

    But silver does not store a magnetic duplicate of the image.
    There's nothing to scan.

  5. #15
    Steve Smith's Avatar
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    Quote Originally Posted by holmburgers View Post
    And yes tape recorders still exist, and I use them to record in my band; you can get new tape from Quantegy.
    There is still a market for Ampex 456. Not as big a market as film but it is still being sold.


    Steve.

  6. #16
    Marco B's Avatar
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    Quote Originally Posted by holmburgers View Post
    Perhaps one of the other "non-silver" photography methods utilize a substance that is ferromagnetic?
    Ah, well, maybe create a "frog-o-type" :



    Levitated in a 16 Tesla magnetic field of a Dutch University laboratory... the frog was alive and well during the procedure (and afterwards AFAIK)...:

    The frog that learned to fly

    Interesting quote from the above linked page:

    "In fact, it is possible to levitate magnetically every material and every living creature on the earth due to the always present molecular magnetism. The molecular magnetism is very weak (millions times weaker than ferromagnetism) and usually remains unnoticed in everyday life, thereby producing the wrong impression that materials around us are mainly nonmagnetic. But they are all magnetic. It is just that magnetic fields required to levitate all these "nonmagnetic" materials have to be approximately 100 times larger than for the case of, say, superconductors."

    By the way, Mustafa, I keep getting a big grin on my face each time I see your completely crazy ideas. Keep them coming, and maybe write a book sometime discussing them all, will be a nice art project.

    Marco
    Last edited by Marco B; 11-17-2010 at 11:31 AM. Click to view previous post history.
    My website

    "The nineteenth century began by believing that what was reasonable was true, and it wound up by believing that what it saw a photograph of, was true." - William M. Ivins Jr.

    "I don't know, maybe we should disinvent color, and we could just shoot Black & White." - David Burnett in 1978

    "Analog is chemistry + physics, digital is physics + math, which ones did you like most?"

  7. #17
    holmburgers's Avatar
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    Whoa Marco, that was awesome!

    Ok, hold the phone. How about toning? Are any of the toning metals magnetic?

  8. #18

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    If it was easy to read silver with a magnetic tape head they would not have used a magnetic stripe on APS film back in the 80's ( http://www.kenrockwell.com/tech/aps.htm see website for reference.) They would have just done something to imprint the emulsion and called it a day.

    I would be willing to bet that about all you would be able to do with a magnetic tape head is figure out that there is silver on the film, and even that will be a stretch.
    "Would you like it if someone that painted in oils told you that you were not making portraits because you were using a camera?"
    "Shouldn't it be more about the joy of producing and viewing the photo than what you paid for the camera?"

    Me

  9. #19
    Worker 11811's Avatar
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    Quote Originally Posted by bblhed View Post
    I would be willing to bet that about all you would be able to do with a magnetic tape head is figure out that there is silver on the film, and even that will be a stretch.
    Yes, you can detect the presence, absence or the amount of silver present on a piece of film using electronic methods. (Eddy current detection, etc.) You can use the absence or presence of silver to encode information, much the way you would record bits of data on paper using dot or bar codes but the silver, itself, can not carry information.
    Randy S.

    In girum imus nocte et consumimur igni.

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    http://www.flickr.com/photos/randystankey/

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