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  1. #11

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    Quote Originally Posted by Greg Davis View Post
    I don't know what you have been reading, but I purchased a set of filters from Thomas Duplex and cut them open to find the Rosco gel numbers still printed on them.
    Wow...that's odd. I just looked up those filters and the wavelengths they allow to pass are not what I would have expected at all. The factory filters that came with mine were horrendously cracked/crinkled gelatin with no printed numbers to be found, and I looked pretty hard to find one just in case I had to cross-reference something. That's very interesting info; thank you!

  2. #12
    Ken Nadvornick's Avatar
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    Quote Originally Posted by Greg Davis View Post
    The filters are wrong. The pair on the moveable vanes should be two sheets of the Rosco #19 with diffusion, but the bottom pair should be a sheet of Rosco #3406 and #3407 with diffusion. This matches the filters that are sold commercially for this safelight.
    Quote Originally Posted by Ken Nadvornick View Post
    I dunno' Greg. For b&w all I use is a single layer of Roscoe #19 Fire between glass sheets without any diffusion. The Roscoe spectral transmission chart says this should be sufficient. And for both my CD and pre-flashed fogging tests of Ilford MGIV, it is.

    This filter is located in the lower filter position. The vanes contain only sheets of black mount board. That allows me to adjust down to total darkness for easel framing and focusing.

    Ken
    Quote Originally Posted by Greg Davis View Post
    I tried that after your posts in the other thread. I had fog after very short times. I test using Kodak's method of using safelight exposure before a medium gray exposure, and again after a medium gray exposure on separate pieces of paper. Using the filters I mentioned gave me safe times after exposure of up to three minutes with the vanes fully open, and well past seven minutes with them fully closed. With just the #19 filter in place I had safe times of less than one minute fully closed after the paper received printing exposure. Just my experience.

    I should note that I was using Ilford MGWT paper. Regular MG gave slightly longer safelight times, though I don't know why since printing times are shorter with MG than MGWT.

    And, yes, I was meticulous about other sources of light being an influence. Even the glow from my watch face was eliminated from the darkroom first.
    Hi Greg,

    This is the first chance I've had to look into this further. I went and checked my set of original FBD filters for my Duplex. I purchased my unit new before they were discontinued so I know they were OEM pieces. They showed no indication of Roscoe product or serial numbers. Could it be that the construction of the filters changed over the product lifetime of these safelights? Mine was purchased quite a few years ago.

    I then had a look at the spectral transmission graphs made available online by Roscoe. There are two very slightly different versions of the #19 Fire filter listed. I've referenced the version I purchased. Here are the three in question for others who may not have seen them:

    Rosco E-Colour+ #019 Fire

    Rosco Roscolux #3406 Sun85

    Roscoe Roscolux #3407 Sun CTO

    And here again is that LPS line spectrum from Brian Niece, Associate Professor of Chemistry at Assumption College in Massachusetts (fourth item down the page):

    Low Pressure Sodium Line Spectrum

    From the generated line spectrum of an LPS lamp the extra blues and greens caused by the inclusion of the argon/neon Penning mixture are readily apparent. And a look at the #19 Fire filter chart shows that it should be almost perfectly opaque to those wavelengths all by itself. For standard OC-rated b&w materials this filter should work fine. And in practice, at least for me, it does.

    On the other hand, I'm not sure what additional safeness the other two filters would add, given their respective charts. Especially in the green regions for VC papers. Filter #3407 in particular allows a substantial percentage of blue-greens and greens to pass. This should be an obvious risk factor for VC papers if the #19 were not present.

    Might these second two filters be intended for different materials? I'm really curious regarding your observed results.

    Ken
    "They are the proof that something was there and no longer is. Like a stain. And the stillness of them is boggling. You can turn away but when you come back they’ll still be there looking at you."

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  3. #13

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    Quote Originally Posted by Ken Nadvornick View Post
    Might these second two filters be intended for different materials? I'm really curious regarding your observed results.
    Well, we need a cross-reference between Thomas' "edge tape color" based ID scheme, and the various gel colors, but as a clue, here are the official instructions from Thomas (I scanned the sheets that came with mine):

    http://backglass.org/duncan/darkroom...ight_instr.pdf

    Duncan

  4. #14
    Greg Davis's Avatar
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    I purchased a set from Freestyle while Thomas was still in business. I bought a yellow tape, a red tape, and a black tape. I took them apart a few years later to see if they were filters I could replace myself for less money. In the yellow tape filter I found two sheets of gel filter material. One had the number 3407, the other 3406. I recognized them as Rosco filters from my sample book. The red tape had "ROSCO 19" printed on the edge of the filter. The black tape did not have any markings, but were the same colors as the yellow tape, but used more layers of filter material inside. All of them used the tissue paper that comes with Rosco filters as the diffusion material.

    The numbers were not present in both filters of a pair. I don't think they were intended to be left on the filter material when cut and put in place. I had a very old set of Thomas Duplex filters, and they were different material. It was far too old and faded to tell what they once were. It is possible that the filters sold for these safelights now and just before Thomas Duplex stopped selling their lights are made by someone else and they just use what they think may work, but if you buy a set of filters from Freestyle or KHB Photographix, these are what you get.

    You could always buy a set, open them, and tell us what is in them. If they are different than what I have, then I was sold the wrong filters. But I doubt it.
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  5. #15

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    Quote Originally Posted by Ken Nadvornick View Post
    From the generated line spectrum of an LPS lamp the extra blues and greens caused by the inclusion of the argon/neon Penning mixture are readily apparent. And a look at the #19 Fire filter chart shows that it should be almost perfectly opaque to those wavelengths all by itself. For standard OC-rated b&w materials this filter should work fine. And in practice, at least for me, it does.

    On the other hand, I'm not sure what additional safeness the other two filters would add, given their respective charts. Especially in the green regions for VC papers. Filter #3407 in particular allows a substantial percentage of blue-greens and greens to pass. This should be an obvious risk factor for VC papers if the #19 were not present.
    This is the part that confuses me. The 19 filter is only supposed to allow the passage of a slight percentage of green-ish wavelengths, and this was very evident in my not-at-all scientific test; there was a definite green band right where one would expect it, were they looking at the chart for the 19 filter. I was under the impression that this wouldn't be an issue when I ordered the 19 and 27 filters, because I'd read so many reports of them being great cutoff filters for the sodium lamp...but somehow I still got a definite graying of the paper after less than a minute's time. With that said, I can't figure out how the other two filter numbers would help, because they seem to be letting in a lot of blue/green wavelengths.

    Quote Originally Posted by frobozz View Post
    Well, we need a cross-reference between Thomas' "edge tape color" based ID scheme, and the various gel colors, but as a clue, here are the official instructions from Thomas (I scanned the sheets that came with mine):
    I just found that online not too long ago; thanks for posting it!

    Quote Originally Posted by Greg Davis View Post
    I purchased a set from Freestyle while Thomas was still in business. I bought a yellow tape, a red tape, and a black tape. I took them apart a few years later to see if they were filters I could replace myself for less money. In the yellow tape filter I found two sheets of gel filter material. One had the number 3407, the other 3406. I recognized them as Rosco filters from my sample book. The red tape had "ROSCO 19" printed on the edge of the filter. The black tape did not have any markings, but were the same colors as the yellow tape, but used more layers of filter material inside. All of them used the tissue paper that comes with Rosco filters as the diffusion material.

    The numbers were not present in both filters of a pair. I don't think they were intended to be left on the filter material when cut and put in place. I had a very old set of Thomas Duplex filters, and they were different material. It was far too old and faded to tell what they once were. It is possible that the filters sold for these safelights now and just before Thomas Duplex stopped selling their lights are made by someone else and they just use what they think may work, but if you buy a set of filters from Freestyle or KHB Photographix, these are what you get.

    You could always buy a set, open them, and tell us what is in them. If they are different than what I have, then I was sold the wrong filters. But I doubt it.
    I think the filters I had in mine when I got it were the older style, as well...and they were desiccated beyond recognition. I'm almost tempted to buy the inner set and see what comes in them...but that may have to wait until I have some extra cash. For now, I'm hoping that the rubylith I ordered will come in soon and hopefully allow me to actually use the safelight, rather than just look at it.

  6. #16
    Ken Nadvornick's Avatar
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    Quote Originally Posted by Sundowner View Post
    This is the part that confuses me...
    And it's confusing me as well. The #19 filter should cut off virtually ALL of the blues and greens. In other words, when in place you should see no blue and/or green bands at all.

    Before my successful (pre-fogged) safelight tests I fired up the Duplex, let it warm for ~30 minutes, then looked at the CD reflections unfiltered. In addition to the massive yellow sodium doublet, I saw the much, much fainter blue and green spikes. I also saw the extra deep red spike.

    Then while looking directly at those spikes I interposed a single layer of #19 filter. The blue and green spikes disappeared. When I removed the #19, they returned. Back and forth.

    Later, when I performed the safelight test I was able to leave a sheet of Kentmere Bromide #3 graded paper out for ~30 minutes with no hint of fogging.* As you may know, bromide papers are very fast. It should have responded to any blue light present. But it didn't. It remained pure white. (Even checked with a reflection densitometer to factor out my subjective eyes.)

    So as I said, I too am confused.

    Also keep in mind that if you use a cover sheet of Rubylith you will likely be filtering out all of the yellow sodium light as well. At least in a perfect world. I've never tried it myself, so I don't know how much will pass. Maybe only that secondary red spike I mentioned above?

    Ken

    * Apologies, as I earlier identified the test paper as Ilford MGIV. It was actually the Kentmere Bromide. The Ilford was used for my red LED safelight testing.
    "They are the proof that something was there and no longer is. Like a stain. And the stillness of them is boggling. You can turn away but when you come back they’ll still be there looking at you."

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  7. #17
    Greg Davis's Avatar
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    In regards to the paper that you left out for 30+ minutes, did you flash it at all to see if there was any effect on top of exposure? My tests didn't show much, if anything, in blank white areas. The degradation was in areas that were already exposed by the enlarger.
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  8. #18
    Ken Nadvornick's Avatar
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    Yes, I did. That's what I meant when I said "pre-fogged." Perhaps not the best choice of words by me. Probably should have said "threshold fogged."

    A test was first made to determine threshold exposure for the Bromide #3 paper. Then the test sheet was pre-exposed to just below that threshold level. Any additional safelight fogging exposure should have therefore been immediately visible after development. Either to my eye, or to the far more sensitive reflection densitometer. Comparisons were made against a similarly pre-exposed control sheet that was not subjected to the safelight.

    It should also be noted that 30 minutes was an arbitrary cutoff by me. Because there was no detectable fogging, the actual safe time limit was therefore an unknown time beyond 30 minutes.

    When I later performed similar testing for a DIY red LED safelight under Rubylith, I extended the test out to 60 minutes without any apparent fogging on MGIV. That's where my earlier incorrect reference to MGIV came from.

    Ken
    "They are the proof that something was there and no longer is. Like a stain. And the stillness of them is boggling. You can turn away but when you come back they’ll still be there looking at you."

    — Diane Arbus, March 15, 1971, in response to a request for a brief statement about photographs

  9. #19

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    Quote Originally Posted by Ken Nadvornick View Post
    And it's confusing me as well. The #19 filter should cut off virtually ALL of the blues and greens. In other words, when in place you should see no blue and/or green bands at all.

    Before my successful (pre-fogged) safelight tests I fired up the Duplex, let it warm for ~30 minutes, then looked at the CD reflections unfiltered. In addition to the massive yellow sodium doublet, I saw the much, much fainter blue and green spikes. I also saw the extra deep red spike.

    Then while looking directly at those spikes I interposed a single layer of #19 filter. The blue and green spikes disappeared. When I removed the #19, they returned. Back and forth.

    Later, when I performed the safelight test I was able to leave a sheet of Kentmere Bromide #3 graded paper out for ~30 minutes with no hint of fogging.* As you may know, bromide papers are very fast. It should have responded to any blue light present. But it didn't. It remained pure white. (Even checked with a reflection densitometer to factor out my subjective eyes.)

    So as I said, I too am confused.

    Also keep in mind that if you use a cover sheet of Rubylith you will likely be filtering out all of the yellow sodium light as well. At least in a perfect world. I've never tried it myself, so I don't know how much will pass. Maybe only that secondary red spike I mentioned above?

    Ken

    * Apologies, as I earlier identified the test paper as Ilford MGIV. It was actually the Kentmere Bromide. The Ilford was used for my red LED safelight testing.
    Well, allow me to make it even more confusing: I did the exact same thing that you did with filtered and unfiltered reflections on the CD. Unfiltered, I saw the blue and green bands, and also the massive yellow sodium band and the deep red...exactly as expected. With the #19 filter in place, the yellow and red were unaffected and the blue was entirely cut out...but the green band was still dimly present. I actually managed to do a side-by-side comparison with the #19 filter halfway covering the sodium lamp, and although the green band was attenuated it was, as aforementioned, present. So, I don't know what to make of that, because there should be very, very little green coming through the #19 filter...but it was most assuredly there, and likely - in my opinion - burning the paper.

  10. #20
    Jim Noel's Avatar
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    I simplified the solution in my 10x10' darkroom. I use the supplied yellow/tan filter over the tube. I inserted black foam core in the vanes to attenuate the light. I have never had a problem with fogging in the 20+ years I have used this light.
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