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  1. #101

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    Quote Originally Posted by Ed Sukach
    I think you'll find that filter wasn't for the absorption of Ultra Violet (very little of a tungsten source spectrum is UV) .. but for the other end; Infra Red ... there is quite a bit of that ... and its' alter ego - heat.
    IR filters are very common in optical system .. they are commonly called "heat glass" or heat filters".
    Yes, the IR filter is common in this type of system and in fact I still have one of these filters installed in the Bes 23-C II that I use for film testing. It is in the form of some type of acryllic of about 1/32" thickness. But I also had a UV filter in there at one time, of that I have no doubt, and to the best of my recollection it either came with the enlarger or was recommended by Beseler. I can not say how much UV the tungsten-halogen bulb in my Beseler 23-C radiates, if any, but I have tested other bulbs of this type with UV processes and and they definitely emit some UV radiation.

    And BTW, Cool-Blue and Daylight fluorescent tube, which most people don't expect would provide mucy UV radiation, are almost as effecive in exposing dichromate colloid processes as real "UV" type tubes, i.e. BL, BLB and SA.

    However, let me make this perfectly clear. I am not claiming that the tungsten lamp in my Best 23C II system is radiating enough UV radiation to affect exposure of panchromatic film. I simply put it out as an idea that deserves some consideration and I intend to test it myself as soon as I have the materials required to do so.



    Sandy
    Last edited by sanking; 08-17-2004 at 11:06 PM. Click to view previous post history.

  2. #102
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    Yes. Kirk, I studied these characteristics of human vision while working in simulation and human factors at NASA Langley Research Center. My question was not about the human resonse curve, but about the response curve of the visual filter in certain densitometers. If it is supposed to duplicate the human response curve, then it should not be used in the kind of work we are talking about in this thread. Nowhere in the system do we have the human resonse curve duplicated by any of our sensitized materials.
    Gadget Gainer

  3. #103

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    Sandy, the BLB (Black Light Bulbs?) tubes you mention - I understand there are at least two types of these tubes. One has a main emission at around 370, and the other aroud 350. Is this correct, and which type do you use?

    Kirk

  4. #104
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    Quote Originally Posted by sanking
    Yes, the IR filter is common in this type of system and in fact I still have one of these filters installed in the Bes 23-C II that I use for film testing. It is in the form of some type of acryllic of about 1/32" thickness.
    I don't mean this to be a win/ lose argument. It is entirely possible for an enlarger manufacturer to do any number of things with the construction of their equipment. Somewhere in this PC, there is a bookmark of a lamp manufacturer's site (Osram??) complete with spectrograhic charts of the output of their lamps. It is true that there is *some* UV emanation from Tungsten and Halogen lamps - but not much. The higher the color temperature of the lamp - the more UV .... That is why most "studio" flash systems - balanced to daylight ~ 5000 - 6000K have "UV" coating... to eliminate fluorescence from fabric "brighteners" and such.

    I DON'T know about Beseler. I DO know that my Omega 5500 does NOT have UV filtration in the optical system of its Color Head.

    It really suprises me that an IR - Heat Glass filter would be made of acrylic. This would be the first plastic heat filter I've ever encountered. The special glass ones I am familiar with (@#$% expensive!! - 50 US$ for the Omega) are very effective - that is, they get HOT!!! Are you sure it was an acrylic filter? If I remember - one of the ways to identify plastics was to burn them ... Nitrocellulose burns very well, a clear, yellow flame... I can't remember what acrylic does, but I think it was either a flame or smoldering and bubbling.
    Carpe erratum!!

    Ed Sukach, FFP.

  5. #105

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    Quote Originally Posted by Kirk Keyes
    Sandy, the BLB (Black Light Bulbs?) tubes you mention - I understand there are at least two types of these tubes. One has a main emission at around 370, and the other around 350. Is this correct, and which type do you use?

    Kirk
    Kirk,

    The BL and BLB tubes are essentially the same tube, the only difference being that the BLB has a filter that cuts off all light above about 420 nm. Since many alternative processes have some sensitivity to light above 420 nm the BL tubes print slightly faster than BLB. BTW, the correct name for these tubes is Black Light and Black Light Blue.

    I have an article on UV light sources for alternative printing at http://unblinkingeye.com/Articles/Light/light.html. There are SPD charts for many of the light sources people are using for printing alternative processes.

    You might be interested to note that the SA and AQUA tubes, which peak at around 420 nm, are also very effective for exposing Pt./Pd. processes. Some people actually find that they print faster than BL and BLB tubes, though that was not true with the tubes I tested. Some of the extra speed from the SA and AQUA tubes is likely due to the fact that glass passes a much higher percentage of radiation at 420 nm than at 350 nm.

    The issues involved with exposing alternative processes are very complicated as you have to balance issues such as UV transmission of glass, the SPD of the light source, and the specific requirements of the process. The good thing is that if you just forgot all this you can make good prints with a rather wide range of light sources, some which in theory would not appear to be good candidates.

    Sandy

  6. #106

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    Quote Originally Posted by Ed Sukach
    It really suprises me that an IR - Heat Glass filter would be made of acrylic. This would be the first plastic heat filter I've ever encountered. The special glass ones I am familiar with (@#$% expensive!! - 50 US$ for the Omega) are very effective - that is, they get HOT!!! Are you sure it was an acrylic filter?
    The filter is some kind of plastic, and it looks to be acrylic. But you may be right in that it is not an IR filter. I could have just assumed that it was when its only purpose might be to just support the filters that go into that slot.

    Sandy

  7. #107

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    Sany wrote, "I have an article on UV light sources for alternative printing at http://unblinkingeye.com/Articles/Light/light.html. There are SPD charts for many of the light sources people are using for printing alternative processes."

    Sandy - thanks for the tip on the article. I guess that makes you the expert on that subject! :^)

    So are you using the Sylvania BLB bulbs for which you have the spectra in the article?

  8. #108

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    Patrick wrote, "Yes. Kirk, I studied these characteristics of human vision while working in simulation and human factors at NASA Langley Research Center."

    Cool! Wish I was there back then with you.

    "My question was not about the human resonse curve, but about the response curve of the visual filter in certain densitometers. If it is supposed to duplicate the human response curve, then it should not be used in the kind of work we are talking about in this thread. Nowhere in the system do we have the human resonse curve duplicated by any of our sensitized materials."

    Patrick, that's true. The response has certainly not been "duplicated". But what is really more important is that some of these things that we are discussing have been standardized. Like the Status A and M filters used in color densitometry. We need to recognize that.

    And where things may not have been standardized, like UV filtration of a densitometer, then finding out peak transmission and bandpass widths are needed too. Determining these things may help with this question, and being explicit about them, like Sandy was when describing his densitometer, will help too.

    I'm sure you can visualize exactly what the properties of a 373 nm with a 45 nm width looks like.

  9. #109

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    Sandy Wrote, "Yes, the IR filter is common in this type of system and in fact I still have one of these filters installed in the Bes 23-C II that I use for film testing. It is in the form of some type of acryllic of about 1/32" thickness."

    Sandy, Ed is right. Acrylic resin is not going to to be a very good IR filter. Remember that IR will heat things up and that will warp or melt the plastic.
    There are special types of glass designed for this purpose.

    Acrylic will not even be a good UV filter. Actually, most organic materials that are colorless are probably going to transmit UV on down to about 200 - 300 at the highest. Not effective as a UV filter.

    "I can not say how much UV the tungsten-halogen bulb in my Beseler 23-C radiates, if any, but I have tested other bulbs of this type with UV processes and and they definitely emit some UV radiation."

    Yes, they do radiate some UV light. But when compared to the amount of visible light they are emitting, it is practically insignificant. I have a spectrophotometer that uses a tungsten bulb and it can read down to 320 nm. But in the design of the instrument, no glass has been allowed in the pathway for the light. Only front surface mirrors and quartz glass have been used to avoid filtering any of the UV.

    I have no doubts that you could make an exposure on a material like Pt/Pd paper with a tungsten light source.

    "I am not claiming that the tungsten lamp in my Best 23C II system is radiating enough UV radiation to affect exposure of panchromatic film. I simply put it out as an idea that deserves some consideration and I intend to test it myself as soon as I have the materials required to do so."

    This could be demonstrated by combining a Wratten 18A filter with your tungsten light. The 18A passes UV from about 320 to 400 nm, centered around 360 nm and filters out visible wavelengths up to about 700 nm where it starts to pass IR. This alone would be ideal for testing your Pt/Pd paper as it will not respond to the IR. You could try it with some panchromatic film, as long as it was not sensitve past 650-680 nm. I have no doubt that you will loose a lot of film speed when compared to the tungsten light alone, daylight corrected or not. Please let us know what you find.

    But practically, he UV component of a tungsten bulb is not sigificant when exposing a step wedge for use with panchromatic film.

    Kirk

  10. #110

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    Sandy - Side Note -
    I've been looking at your UV light source article you recommended http://unblinkingeye.com/Articles/Light/L2/l2.html , and I have a question - you say, "Speed was determined by the first step wedge that provided maximum density"

    Why did you pick that? Doesn't film testing convention say that you should have used the first step that showed any density? That's how regular film speeds are determined. And paper speed points are a middle grey. Why did you use maximum black?

    Sorry for the side trip, but I'm curious.



 

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