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  1. #11

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    Quote Originally Posted by rmazzullo View Post
    I guess I'll have to wait until an electron microscope comes up for sale on e-bay.
    Hey, if you've got the bucks and can figure out how to use and maintain it, why shortchange yourself?

  2. #12

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    HAPPY HOLIDAYS TO ALL EMULSION MAKERS !
    There are many electron microscopes on ebay! Price ranges from under a thousand dollar to the mid 10s of thousands. I am gonna stick with my optical scopes. I have known people who had full time jobs just preparing samples for and running those things.
    Bill

  3. #13
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    Quote Originally Posted by Jim Noel View Post
    PE beat me to the punch.
    What you are seeing with an optical microscope is not the grains, but clusters of grain.

    With an optical microscope, you see a hint of the silver halide grain as translucent dots before development. After development you see black threads, clumps and dots of silver metal.

    I forgot to mention that here, sample prep involves gluing the emulsion side of the film to a substrate very firmly before microtoming in order to prevent deformation or destruction of the emulsion layer. And, photmicrographs of raw emulsion are rather rare.

    With an electron microscope, you see the crystal as it actually is.

    Electron micrographs run from about $150 to 500 each depending on lab service offered and quantity done at one time.

    Both types of imaging have been done on emulsions and pubilshed in textbooks, but electron micrographs are the preferred method for raw emulsion and photo micrographs are preferred for film cross sections.

    PE

  4. #14
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    a "possible" alternative...

    Here are a couple of links to the web pages of two people who built a scanning tunneling microscope, that alleges a ~1 micrometer resolution...for very cheap money.

    http://www.geocities.com/spm_stm/Project_overview.html

    --and--

    http://www.e-basteln.de/index_o.htm

    hmmm...maybe I don't have to spend big bucks on e-bay after all.....

    (go to this link to see a 1.25 um x 1.25 um image: http://www.geocities.com/spm_stm/Progress.html)

    Bob M.

  5. #15
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    Bob;

    This is not the same thing. See the photo quality images that I posted elsewhere at the 1 micron resolution.

    PE

  6. #16
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    PE,

    I should have mentioned that my post was meant more for it's novelty value than for any real practical use.

    Oops.

    Bob M.

  7. #17

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    electron microscope

    Scientific American published instructions for making an electron microscope at home. Martin Gardner's column, I believe. Check the indexes from 30 to 40 years ago. If I remember right, it involved little more than the kind of parts, equipment and glass work they use at neon sign places.

    ...just can case anyone is getting bored ...

  8. #18

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    My 1950's microscope is OK for making photomicrographs of edge effects and of negatives of resolution charts but grain(clumps) is a bit beyond it. Attachment,IIRC FP4 in Pyrocat HD with a 40x objective was hard to focus and dim.A modern microscope might do better.
    Attached Thumbnails Attached Thumbnails grain.jpg  

  9. #19
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    Well, here are some things to consider when wanting to look at the internal structure of a film:

    1. Looking at the raw emulison - use an Electron Microscope or a Scanning Electron Microscope. Sample prep is critical to see the grains, and resolution must be on the order of 1.0 micron or smaller in the case of paper emulsions. Don't forget the words "SAMPLE PREP". These were done in a special lab. I did quite a few, but never ran the instrument.

    2. A microdensitometer is used to look at edge effects. I have posted examples here on APUG. I did a lot of these, but never ran the instrument.

    3. Grain is measured as RMSG (Root Mean Square). To do this a microdensitometer is used with special software / hardware to derive the grain profile. A sample is scanned across a given step to get the RMS of the deviation in density. I have no examples, but used to do this often. I never ran this instrument.

    4. To look at film structure, you need a microtome and a method of laminating the film to another substrate. You cut sandwiches of this and look edge on to see the structure. Silver grains and silver can be seen as tiny dots with no resolution. Usually, the magnifiacation is about 2500x and an oil immersion lens is used. I did a lot of these myself but was never what you would consider an expert.

    PE

  10. #20

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    Hardly anyone has a microdensitomer.Ilford have one, Geoffrey Crawley has one,that's all I have been told.
    Would a modern microscope be any use at all? The objective would need high magnification,how high?

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