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  1. #31

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    I am sure that the new light source must be UV in that Michael related that it is not "hot". Additionally Azo (according to the Kodak spectral sensitivity curve on the material) exposes entirely in the 360-410 nm UV band. This is near band UV or A band in the three band method of classification. This light probably still in the visible spectrum (at least the upper 410nm band would be) that focus shift would not be a consideration.

    This new light source is probably useable only on Azo, unless a secondary light source is incorporated into the system.

    The "new" Durst 5X7 enlarger which is useable on both Pt-Pd and Azo is designed for UV output. This enlarger is scheduled for 3-03 release. And, once again, useable only for the materials noted.
    Art is a step from what is obvious and well-known toward what is arcane and concealed.

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  2. #32
    Eric Rose's Avatar
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    Maybe it uses the same bulbs as tanning beds. I wonder if anyone has ever tried to expose their contact print in a tanning bed just to check it out.
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  3. #33

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    I imagine that it would expose, Eric, although I have not tried that myself. I think that the problem that exists, and apparently is being solved by others, is getting enough light intensity to pass through to the easel. The enlarging lens does "choke" things down a bit. I visited with a fellow on another forum and he related that while Azo is very slow (paper speed 6) vs polycontrast (paper speed 150) it is still a lot faster then pt-pd and he had contact printed Azo under his UV printer for pt-pd.
    Art is a step from what is obvious and well-known toward what is arcane and concealed.

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  4. #34
    glbeas's Avatar
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    </span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (Ed Sukach @ Mar 21 2003, 08:51 AM)</td></tr><tr><td id='QUOTE'> </span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (glbeas @ Mar 20 2003, 02:15 PM)</td></tr><tr><td id='QUOTE'></span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (Michael A. Smith @ Mar 20 2003, 06:07 PM)</td></tr><tr><td id='QUOTE'> You all should know that there will be a light source coming soon (the patent has been applied for) that will enable one to enlarge on Azo. </td></tr></table><span class='postcolor'>
    ...will this be using the visible blue end or the uv spectrum to expose Azo? If it&#39;s uv would there be any problems with focus shift like you have with infrared?</td></tr></table><span class='postcolor'>
    How would one notice a &quot;focus shift&quot; in the enlarger? - Or would this be switchable from &quot;Ordinary&quot; to &quot;Special for AZO&quot;? </td></tr></table><span class='postcolor'>
    Same way you notice the focus shift when shooting infrared, it comes out fuzzy&#33;
    Focusing in visible light and shooting in a non visible wavelength can give errors if the lens doesn&#39;t focus the same at all wavelengths, and most lenses are corrected for visible light.
    Gary Beasley

  5. #35
    Ed Sukach's Avatar
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    </span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (glbeas @ Mar 21 2003, 11:57 AM)</td></tr><tr><td id='QUOTE'>Same way you notice the focus shift when shooting infrared, it comes out fuzzy&#33;
    Focusing in visible light and shooting in a non visible wavelength can give errors if the lens doesn&#39;t focus the same at all wavelengths, and most lenses are corrected for visible light.</td></tr></table><span class='postcolor'>
    Hmmm ...

    This is one thing I have been meaning to check out. I have read quite a bit about IR and have wrestled with the focus problem.
    "Fuzzy" - I am famliar with.
    The last I&#39;ve read, and I&#39;ve reconciled it with the optical theory that I know, is that any "focus shift" will be directly proportional (but not linearly) to the wavelength of light in question; and given the IR sensitivity of films like Konica 750, Ilford&#39;s SFX, MACO 820 ... and what was that extended red range film from Agfa? ... AND the fact that when using a SLR with a Red #25 or 29 fiter in place, a great deal of the non-affective wavelength will be eliminated, the most common error is to OVER-compensate. With films &#39;way out there in the IR spectrum, e.g., Kodak&#39;s HIE and opaque filters (87&#39;s and 89&#39;s) - the usual 10% or so, applied *after* focusing IS valid.

    In enlarging, a LOT is going to depend on the actual spectrum from the new light source. If my memory of Geometrical Optics serves, there will be relatively less shift with shorter wavelengths. Another factor will lie in the fact that ordinary glasses, including optical glasses used in enlarger lenses, filter out UV rather effectively - See the Hasselbad UV lens with Flouride elements.

    So ... If this light source operates in blue-visible- to- near UV, I doubt that there will be much "shift. If it produces light across the visible spectrum to far (or properly "more distant") UV there could be. "Far" UV is not likely - the human eye will flouresce beyond a certain wavelength and that *IS* uncomfortable.

    More "complications" for the perfectionists among us -- all the time.

    Carpe erratum!!

    Ed Sukach, FFP.

  6. #36

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    I don&#39;t know whether this is factual or not...however I have been told this by someone who should know... The El Nikor lenses are among those that have the capability of transmitting the UV spectrum in which Azo paper is exposed. However, I have also been advised that conventional enlarging lenses are fairly effective in blocking UV transmission. There are apparently quartz elements in some of the more exotic optical systems that are most effective in passing UV. In fact metal halide lamps have a quartz envelope in most cases.
    Art is a step from what is obvious and well-known toward what is arcane and concealed.

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  7. #37
    Ed Sukach's Avatar
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    </span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (dnmilikan @ Mar 21 2003, 01:33 PM)</td></tr><tr><td id='QUOTE'> There are apparently quartz elements in some of the more exotic optical systems that are most effective in passing UV. In fact metal halide lamps have a quartz envelope in most cases.</td></tr></table><span class='postcolor'>
    The reason for using quatz is that it has a *very* high melting point - much higher than glasses. Halogens, etc., get *hot*.

    I can only remember two outstanding attributes of crystalline quartz - It has a very high index of refraction; and it can be made without "inclusions" that would cause the energy from a laser to be "grabbed" - 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 "Iceland Spar", otherwise known as "Calcite" or "Fluorite".
    Interesting stuff - Calcite is also the only material with two (2) indices of refraction.
    That DOES complicate optical design.

    BTW - That Hasselblad UV lens is listed at something like &#036;US 10K.
    Carpe erratum!!

    Ed Sukach, FFP.

  8. #38

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    Ed,
    I was under the distinct impression that acrylic was more resistant to uv transmission then glass. At least that is what my supplier has indicated to me. Am I correct, or have I been misinformed?

    At that price, I think that I may have to order a couple of the blad lenses...how many for you?
    Art is a step from what is obvious and well-known toward what is arcane and concealed.

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  9. #39
    Ed Sukach's Avatar
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    </span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (dnmilikan @ Mar 21 2003, 03:34 PM)</td></tr><tr><td id='QUOTE'>&nbsp;
    I was under the distinct impression that acrylic was more resistant to uv transmission then glass. At least that is what my supplier has indicated to me. Am I correct, or have I been misinformed?

    At that price, I think that I may have to order a couple of the blad lenses...how many for you?</td></tr></table><span class='postcolor'>
    Acrylic filters out very little UV by itself. Coatings can be applied to absorb UV - as is done regularly with sunglasses... and some of the acrylic sheeting used to take the place of glass in frames (about double the price and scartches like crazy).

    Glass on the other hand - It is pretty futile to try to get a tan in a Greenhouse or a glass- enclosed porch.
    Carpe erratum!!

    Ed Sukach, FFP.

  10. #40

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    Ed,
    Thank you for clearing that up for me. I understand what you are saying and what the basis for my suppliers claims were. Thanks again.
    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



 

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