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  1. #11

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    This might be close--:>)
    http://www.enterprisemission.com/moon5.htm

    .......
    When earth and sun are frozen clods,
    When, all its matter degraded
    Matter in aether shall have faded,
    We, that is, all the work we’ve done
    As waves in aether, shall for ever run
    In swift expanding spheres, through heavens beyond the sun.

    Great Principle of all we see,
    Thou endless Continuity!
    By thee are all our angles gently rounded

    -James Clerk Maxwell

    http://www.southalabama.edu/mathstat.../last.poem.pdf

  2. #12
    David A. Goldfarb's Avatar
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    Duplicate threads merged.
    flickr--http://www.flickr.com/photos/davidagoldfarb/
    Photography (not as up to date as the flickr site)--http://www.davidagoldfarb.com/photo
    Academic (Slavic and Comparative Literature)--http://www.davidagoldfarb.com

  3. #13

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    Allow me to ask what's probably obvious to everyone else - Are these the "T" grains we'd all like to make with double run emulsions?

    (preferably , Computer vAg Controlled, sensitized with unobtanium dye, and impossibly perfectly coated )

  4. #14
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    They would have to be controlled, but what the run conditions are I don't know offhand.

    They are apparently not T-Grains.

    PE

  5. #15

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    So looking at my crystal shape diagram someone posted a while back - These are the corner nibbled cubes that are produced when pAg is around 7.5 - 8. T grains (the flat octahedral ones) are made around 9.5.

    So in our single run emulsions where pAg (or vAg, if that is what we are measuring) is not held constant - do we have a multitude of grain types, or do the grains shift as the emulsion ripens?

  6. #16
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    In a single run, the vAg shifts as the run continues and you get a variety of shapes and sizes which we call K grains (Klunkers). The emulsion in question would probably look like a soccer ball. It requires a double run.

    If ammonia is present, or another solvent, in a single run, the grains tend to one size and shape but are rather amorphous giveing smooth rounding tending towards spherical. Without the solvent, and with control, the ends and edges tend to be sharp and well defined.

    PE
    Last edited by Photo Engineer; 12-17-2009 at 06:34 PM. Click to view previous post history. Reason: spelling

  7. #17

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    Quote Originally Posted by Photo Engineer View Post
    Octahedra = 8 sided, Tetra deca hedra = 4 10 sided. An octahedron in emulsion parlance in the case above is a cube with clipped corners. A cube has 6 faces and 8 corners. If you look closely at my photomicrograph, you see that each side has 6 edges but there are 8 + 6 sides making 14. Go figure!

    There are several possible shapes possible. AFAIK, there is nothing "golden" or special about them.

    PE
    Exactly.
    An octahedron is a cube with clipped corners,
    but only if they are clipped in such a way so as to compleatly eliminate the [100] faces of the cube.

    Shallow clipping that only reduces the area of cube faces but does not elimnate them, produces tetradecahedral grains
    (the 6 cube faces + the 8 slightly truncated corners)

    Yes...
    "Golden Tetras" was something that sprung up in my mind from once having had an interest in Tropical Fish.

    My dendrites were streching!

    Ray

  8. #18
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    But Ray, there would be nothing special about them AFAIK. Except the difficulty making them.

    PE

  9. #19

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    That is a good point.

    But it suggests a question:
    What advantages do the various grain types offer?

    If digital imaging had not encroached upon the advancement in silver halide imaging,
    do you think the variety of grain types used in actual products would have increased
    (optimizaton by specialzation) or decreased (optimizaton by progress toward common goals)?

  10. #20
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    Well, aside from amorphous, there are cubes, octahedra, tetrahedra, pyramid and t-grains to mention a few. Each has advantages and disadvantages, but I'm not sure I am the person to describe these fully.

    T-Grains offer high speed, finer grain and better sharpness in many cases. Cubes offer similar advantages, especially fine cubes in print films. A mix of these two are uesd in the new Ektar 100 according to Kodak literature.

    Then there are thick and thin T-Grains. Well, you get the picture.

    Entire textbooks could be written on these subjects alone. And then you get into the epitaxial crystals and the different halide ratios and the field expands from there.

    So, to answer you, we saw this in Ektar 100 so the answer is yes. We were on the brink of something. OTOH, the yield was getting slower per unit of money spent, so we knew that the well was going dry. By some estimates, we might have had that 25,000 speed film by now or maybe higher. IDK. I'm sure we would have had a better Kodachrome. JK.

    PE

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