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  1. #31
    clayne's Avatar
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    When the thread has taken it to the point of which type of cinematic material is on each DVD used for spectral comparison then I know we've hit gold; I'm not surprised Ken has taken us there too. :-)

    FWIW: I also have a Thomas Duplex, used it with vanes just about fully closed and never experienced fogging with either MCC110 or Emaks graded papers. However, I didn't use it 100% of the time because it was just too bright for my 10 by 16 by 12' (ceilings) garage darkroom at the time. When I did use it I used it in addition to 2 ceiling banked red LED safelights. I did not remember seeing any kind of fogging as a result of this safelight.

    I did use the included filters (they're translucent red) at all times - just that the vanes were sometimes slightly open. I never used it without filters.
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  2. #32
    Greg Davis's Avatar
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    Ken, I will send you some extra. Don't worry about sending it back. I already have some pre cut to fit the lower slots. I will include the tissue paper since that is how a filter that is purchased would be used. I am going to test mine again using regular MGIV today because it is faster than MGWT. This time it will be tested fully closed rather than open to see if I get more then 3 minutes, which shows fog with the vanes fully open.

    On another note, I tested the yellow and black edged filters with the vanes fully closed with Kodak RA4 paper awhile back. These both use the same 3406 and 3407 material, but the black tape filter has more sheets in it. It tested to 7 minutes +, so maybe it is filtering something out that a disc just isn't showing.
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  3. #33
    Greg Davis's Avatar
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    Ok, so I just did another test, this time with the vanes fully closed and using the faster speed Ilford MGIV. No fogging at all up to 7 minutes. For those that haven't bothered looking at Kodak's instructions, the paper is exposed to the safelight in steps of 1, 2, and 4 minutes, creating 1, 3, and 7 minutes patches. I may try another one later that is 5, 10, and 20 minutes (5, 15, 35 minutes total), but since that means standing in my darkroom with nothing to do for more than a half an hour, I am not enthusiastic about trying it.
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  4. #34

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    Quote Originally Posted by Ken Nadvornick View Post
    Here's what I did...

    Covered both slots with a single layer of filter material.
    Filter material was Rosco #19 Fire polyester.
    Filter material was not sandwiched between glass sheets.

    Here's what I saw...

    Both blue bands gone.
    A single reduced green band still visible, the 1 red band still visible.
    The sodium yellow intensity was moderately reduced.
    That's basically what I got. Faint green, huge yellow, moderate red.

    Quote Originally Posted by Ken Nadvornick View Post
    Here's what I did...

    Covered both slots with a double layer of #19 filter material.

    Here's what I saw...

    Both blue bands gone.
    Both green bands gone.
    One red band still visible.
    The sodium yellow intensity was severely reduced.
    I haven't tried doubling the filter, yet, but I think I'll give it a shot.

    Quote Originally Posted by Ken Nadvornick View Post
    And here's what I think...

    All my original observations were made using the DVD for the movie The Hunt for Red October.* I now see that different discs have very different reflection characteristics. My original observations showed no residual blues or greens through a single layer of #19. Using the FWAAF disc I now see a definite residual green band.

    My original paper fogging tests were made using only pre-threshold-exposed Kentmere Bromide #3 sheets. This should be a blue-sensitive only paper. It showed no fogging even after 30+ minutes.

    Based on what I saw tonight, I now need to try Ilford MGIV VC blue/green paper to see if that residual green band makes a difference. Based on Sundowner's results, I would expect it to fog on the low contrast end to some detectable level when using my single sheet of #19 material. Then I need to try doubling up the sheets.
    I hadn't really thought that different discs would show different bands, but I guess that could easily be true; I only used the one disc and I got the blue/green/yellow/red pattern you described...but I'm still confused as to why I got so much fogging when I threw the #27 filter over top of the #19, because that should have been a total cutoff of anything that could hurt the paper, regardless of sensitivity...unless something silly was happening: porous filter, paper emulsion acting screwy, etc. That's why I'm going to try the rubylith; it should be paper-safe, and if I still get fogging then something completely odd is happening.

  5. #35

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    Okay, quick update with some results: I tried the non-scientific eight-minute coin test again, just now. I used a single layer of rubylith between two sheets of glass in the lower filter position and sealed up all possible light leaks on the safelight; the safelight itself was allowed to warm up for about 20 minutes or so. After developing the test strip in complete darkness I can't see any traces of fogging or coin silhouettes...so in addition to being ecstatic at having made progress, we now know two things:

    1) The rubylith layer effectively cuts the blue-green bands out and acts as an effective filter.
    2) The paper emulsion is more than likely intact, which makes sense because it's being stored properly.

    At this point, I think my next step is to flash the paper to its threshold and do a more accurate test, and to try installing some opaque panels in the vanes; the rubylith cuts a lot of the overall light, but it's still ridiculously bright in the darkroom and a bit less light would be appreciated when working over an enlarger easel.

  6. #36
    Ken Nadvornick's Avatar
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    A quick caveat regarding the possibility of using Rubylith as a Duplex filter replacement. The Rosco filter sheets are made of a rugged heat-resistant polyester material as they are intended to filter theatrical lighting. Using them in a Duplex should be right up their design alley.

    But Rubylith I'm not so sure about. I don't know what it's made of. Or the coloring agent that is used. Or how those may stand up to the prolonged heat from close proximity to an LPS lamp. I've never tried using Rubylith for a six or eight hour darkroom session, let alone a dozen of those in a row over time.

    Remember also, the Rubylith cuts out a lot of light because it's absorbing that energy. It is not a dichroic medium. And absorbing energy means it will get hot. So at a minimum it may fade somewhat quickly. Or at the other end of the scale it may fail catastrophically. Or it may be just fine. I don't know for sure.

    Just something to keep in mind...

    When I receive the other filter samples that Greg is kindly offering I intend to continue testing to try and get to the bottom of this. Unfortunately I don't often have large blocks of free time, so it may take awhile. I can post frequently to APUG because I sit in front of computers writing software all day. But I don't always have big chunks of disposable time otherwise.

    Ken
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  7. #37

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    Quote Originally Posted by Ken Nadvornick View Post
    A quick caveat regarding the possibility of using Rubylith as a Duplex filter replacement. The Rosco filter sheets are made of a rugged heat-resistant polyester material as they are intended to filter theatrical lighting. Using them in a Duplex should be right up their design alley.

    But Rubylith I'm not so sure about. I don't know what it's made of. Or the coloring agent that is used. Or how those may stand up to the prolonged heat from close proximity to an LPS lamp. I've never tried using Rubylith for a six or eight hour darkroom session, let alone a dozen of those in a row over time.

    Remember also, the Rubylith cuts out a lot of light because it's absorbing that energy. It is not a dichroic medium. And absorbing energy means it will get hot. So at a minimum it may fade somewhat quickly. Or at the other end of the scale it may fail catastrophically. Or it may be just fine. I don't know for sure.

    Just something to keep in mind...

    When I receive the other filter samples that Greg is kindly offering I intend to continue testing to try and get to the bottom of this. Unfortunately I don't often have large blocks of free time, so it may take awhile. I can post frequently to APUG because I sit in front of computers writing software all day. But I don't always have big chunks of disposable time otherwise.

    Ken
    I haven't found that the housing seems to get very hot in a couple hours' time, but I'll certainly keep this in mind; hopefully, rubylith wouldn't fade over a three- to six-month period or fail in catastrophic fashion. As far as the light-cutting is concerned, the amount that passes the filter is enough to keep the room REALLY BRIGHT; I'm going to have to cut it down further to see anything on the easel. I'll be really interested in seeing your results from Greg's filters; thus far I think we've had a lot of good information in this thread and I'm hoping that there will be more coming.

  8. #38
    George Nova Scotia's Avatar
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    I've been following this thread and must say that I've run into a similar problem with the Thomas Duplex and Ilford Warmtone paper using Rosco 19 Fire & even adding some layers of a Rosco Red. MGIV is fine, just the WT (FB in my case). I also have two of the Kodak "beehive" style lamps with Kodak OC filters & 15w bulbs - this setup is clean up to 20 minutes - I got bored after that. I wasn't ready to use the WT paper & with the OC filters that's about as far as I went.

    Keep up the good work.

  9. #39
    Greg Davis's Avatar
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    Another follow-up. I conducted the test again with Ilford MGWT, but with the vanes fully closed. As before, I am using the yellow tape filter in the bottom, which contains 3407 and 3406 Rosco filters, and a red tape filter in the vanes containing a sheet of #19 Fire.

    No fogging after 7 minutes. With the vanes open I had fogging at the 3 minute mark.

    I extended the test to 3, 9, and 21 minutes, 3x the original test. Vanes still fully closed.

    No fogging at all.
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  10. #40

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    Quote Originally Posted by George Nova Scotia View Post
    I've been following this thread and must say that I've run into a similar problem with the Thomas Duplex and Ilford Warmtone paper using Rosco 19 Fire & even adding some layers of a Rosco Red. MGIV is fine, just the WT (FB in my case). I also have two of the Kodak "beehive" style lamps with Kodak OC filters & 15w bulbs - this setup is clean up to 20 minutes - I got bored after that. I wasn't ready to use the WT paper & with the OC filters that's about as far as I went.

    Keep up the good work.
    Maybe there's something different in the emulsion, perchance? I'm not using a warm tone paper but from what I can tell, Oriental VCFB is pretty sensitive to green...so maybe you're in the same situation as me.

    Quote Originally Posted by Greg Davis View Post
    Another follow-up. I conducted the test again with Ilford MGWT, but with the vanes fully closed. As before, I am using the yellow tape filter in the bottom, which contains 3407 and 3406 Rosco filters, and a red tape filter in the vanes containing a sheet of #19 Fire.

    No fogging after 7 minutes. With the vanes open I had fogging at the 3 minute mark.

    I extended the test to 3, 9, and 21 minutes, 3x the original test. Vanes still fully closed.

    No fogging at all.
    Okay, well that partially explains the confusion I had on how the 3406 and 3407 filters were blocking the correct wavelengths; somehow, I missed you having a 19 filter in the vanes. That makes more sense, now; it sort of makes me even more confused about the WT paper, but right now I'll accept partial confusion as a form of progress.

    I'm going to try a longer test tonight and see where I get.

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