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  1. #41

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    Well, whatever the light source, I look forward to it and hope it will be practical for us.

    dgh
    David G Hall

  2. #42

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    David, I agree. The more immediate problem seems to be whether Kodak is going to keep Azo Gr.3 in their product line. I certainly hope that Michael and Paula are able to prevail in their efforts. In lieu of that, maybe the thing that I should be looking toward is putting in a walk in freezer to stock up on the Gr 3.
    Art is a step from what is obvious and well-known toward what is arcane and concealed.

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  3. #43
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  4. #44
    Ole
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    </span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (Ed Sukach @ Mar 21 2003, 02:52 PM)</td></tr><tr><td id='QUOTE'> I can only remember two outstanding attributes of crystalline quartz - It has a very high index of refraction; and it can be made without &quot;inclusions&quot; that would cause the energy from a laser to be &quot;grabbed&quot; - absorbed and converted to heat.... LOTS of heat.

    Plastics, generally, are transparent to UV. The only other material I know of with the requisite transparency is &quot;Iceland Spar&quot;, otherwise known as &quot;Calcite&quot; or &quot;Fluorite&quot;.
    Interesting stuff - Calcite is also the only material with two (2) indices of refraction.
    That DOES complicate optical design.
    </td></tr></table><span class='postcolor'>
    Ed,

    As a geologist I have to protest. "Iceland Spar" is Calcite, calcium carbonate. Fluorite is calcium fluoride; not the same thing at all. Fluorite has only one index of refraction, MOST other minerals - including quartz - have at least two. Calcite has one of the most pronounced differences, giving rise to the double refraction.

    What is usually ment by "quartz" in optics is fused silica, a glass with the same chemical composition as quartz. But unlike the mineral, glass (all glasses) has only one index of refraction. Crystalline quartz does funny things to light, like rotating polarized light or splitting it into two beams. Not very useful in (photo-)optics.

    Calcite was earlier used to make polarizers for microscopes, I know of no other optical use.

    Fluorite has very low dispersion, and has been used in some very expensive lenses.
    -- Ole Tjugen, Luddite Elitist
    Norway

  5. #45
    Ed Sukach's Avatar
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    [QUOTE=OleTj,Mar 24 2003, 12:04 AM]
    Quote Originally Posted by Ed Sukach,Mar 21 2003, 02:52 PM
    I can only remember ....
    Oh, picky, picky...&#33;&#33;

    This just illustrates how *time* can attenuate one&#39;s memory. However, this is the first I&#39;ve heard of *many* minerals having more than one index of refraction... either my training was not that microscopically (pun intended) precise, or the differences between the indices was not pronounced enough to be included .... come to think of it .... they both mean the same...

    To the filing cabinet in my darkroom...

    Well ... I&#39;m gaining ... The Hasselblad lens I&#39;m thinking of is:

    "20134 Zeiss UV-Sonnar CF f/4.3 105mm

    A special purpose lens for photography within the ultraviolet spectrum. It is sensitive to radiation from 215 nm to 700 nm (2150 - 7000 A ~with little circle over~ gstroms), i.e. from short-wave ultraviolet to the initial part of the infrared range. The lens can be pre-focused for ultraviolet in visible light without requiring refocusing for use in the UV range."

    I&#39;ve seen more information about the construction of this lens ... typically - I can&#39;t (#&#036;@%@#&#036 find it. Never can, when I NEED it.

    As far as quartz/ fused quartz - I did a lot of work in physical optics - Spectrophotometry, Optical QC, - and a LOT of Interfereometry ... most of the optical flats we used were "Fused Quartz", (much more durable than glass) and minor defects, e.g. "seeds" (bubbles) and whatnot were not uncommon, and had no effect of the operation. I did a LOT of calibration, optical polygons and the like - Autocollimators, Theodolites ...
    Ah, Theodolites ... a sort of "super transit" with, commonly, 40x telescopes over optically read scales. I worked in Cambridge, Massachusetts - a lively avant-garde College town... and I had a set up on the sixth floor, where I would check "Infinity focus" by training the telescope on certain windows....

    Crystalline quartz components were used - and necessary - in laser optical testing - for Modulation Transfer Functions - precisely for their *absence* of what would be minor defects in ordinary optical bench testing.

    I remember one "Commercial" use for Crystalline quartz - in cylindrical form. It was used to convert a laser beam (of xDiameter) to a one meter - or so - *line*.

    Carpe erratum!!

    Ed Sukach, FFP.

  6. #46
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    I just had a thought after reading all of the comments on UV enlarging lights for AZO. How are you supposed to work with this light source without going blind? Isn&#39;t UV light very bad for your vision?I know I wouldn&#39;t want to be looking through a grain magnifier at a UV light source, unless they build in some kind of removable UV blocking focusing filter. Anyway that is just a thought.
    Scott Stadler

  7. #47
    Eric Rose's Avatar
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    It is also a major contributor to skin cancer.
    www.ericrose.com
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    "civility is not a sign of weakness" JFK

    "The Dude abides" - the Dude

  8. #48

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    There are three different designations of UV emission. The primary health hazard lies below the near band which is required to expose Azo and Pt-pd prints. The far band is particularly nasty stuff, from what I understand. Obviously caution is still in order even with the near band but the hazard is not as great as is commonly attributed.
    Art is a step from what is obvious and well-known toward what is arcane and concealed.

    Visit my website at http://www.donaldmillerphotography.com

  9. #49

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    </span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (Ed Sukach @ Mar 25 2003, 01:15 AM)</td></tr><tr><td id='QUOTE'> and I had a set up on the sixth floor, where I would check &quot;Infinity focus&quot; by training the telescope on certain windows....

    </td></tr></table><span class='postcolor'>
    A good and practical use&#33;

  10. #50
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    </span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (Nige @ Mar 24 2003, 02:44 PM)</td></tr><tr><td id='QUOTE'> </span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (Ed Sukach @ Mar 25 2003, 01:15 AM)</td></tr><tr><td id='QUOTE'> and I had a set up on the sixth floor, where I would check &quot;Infinity focus&quot; by training the telescope on certain windows....

    </td></tr></table><span class='postcolor'>
    A good and practical use&#33; </td></tr></table><span class='postcolor'>
    Especially at night when ....... LOL
    www.ericrose.com
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    "civility is not a sign of weakness" JFK

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