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  1. #41
    Greg Davis's Avatar
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    Well, these are designed to have the yellow tape filter in place for all safelight purposes, and only the filter in the vanes are changed to suit the specific material being handled. The 3406 filter is very similar to an Wratten 85B filter for excess blue, and the 3407 is a Wratten 85B with 3 stop ND. This filter may just attenuate the spectrum a small amount, but mostly knock down the intensity of the bulb. The filter in the vanes would shift the spectrum for the appropriate light sensitive material, whether it is orthochromatic, VC paper, RA4, x-ray, etc.

    I don't know, I am just thinking out loud.
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  2. #42

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    Quote Originally Posted by Greg Davis View Post
    Well, these are designed to have the yellow tape filter in place for all safelight purposes, and only the filter in the vanes are changed to suit the specific material being handled. The 3406 filter is very similar to an Wratten 85B filter for excess blue, and the 3407 is a Wratten 85B with 3 stop ND. This filter may just attenuate the spectrum a small amount, but mostly knock down the intensity of the bulb. The filter in the vanes would shift the spectrum for the appropriate light sensitive material, whether it is orthochromatic, VC paper, RA4, x-ray, etc.

    I don't know, I am just thinking out loud.
    Actually, that makes a lot of sense. Nice thought process!

  3. #43
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    So was the original scenario that the light was being used with only half the filters? Yeah that would definitely do it - you need the filters no matter what.
    Stop worrying about grain, resolution, sharpness, and everything else that doesn't have a damn thing to do with substance.

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  4. #44

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    Quote Originally Posted by clayne View Post
    So was the original scenario that the light was being used with only half the filters? Yeah that would definitely do it - you need the filters no matter what.
    Well, my original scenario was the #19 filter in the lower position and the #27 filter in the vanes, but I got fogging even with the vanes completely closed; Greg's setup isn't the same as the one I had.

  5. #45
    Ken Nadvornick's Avatar
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    And to make things worse, my original scenario was single sheets of #19 in the lower position, and black mount board in the vanes to allow for controlling intensity. Pre-threshold-exposure testing with (presumably blue-only sensitive) Kentmere Bromide showed no fogging out to at least 30 minutes.

    The problem may be that #19 alone works well to block the two residual blue bands present, but only partially blocks the two green bands also present. These bands, along with an additional deep red one, likely arise from the Penning Mixture gases (argon and neon) also present in the lamp to assist with initial striking.

    In other words, Bromide is OK, but Ilford VC is not, depending on exposure times.

    Ken
    Last edited by Ken Nadvornick; 09-13-2013 at 06:57 PM. Click to view previous post history. Reason: Always use consistent descriptive wording...
    "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

  6. #46

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    Quote Originally Posted by Ken Nadvornick View Post
    And to make things worse, my original scenario was single sheets of #19 in the lower position, and black mount board in the vanes to allow for controlling intensity. Pre-threshold-exposure testing with (presumably blue-only sensitive) Kentmere Bromide showed no fogging out to at least 30 minutes.

    The problem may be that #19 alone works well to block the two residual blue bands present, but only partially blocks the two green bands also present. These bands, along with an additional deep red one, likely arise from the Penning Mixture gases (argon and neon) also present in the lamp to assist with initial striking.

    In other words, Bromide is OK, but Ilford VC is not, depending on exposure times.

    Ken
    That's exactly my line of thinking at current; #19 has been reported to be a successful replacement in too many instances for me to think that it just doesn't work, but I think that - like most things - it only works well in certain situations. From the information here and my own observations it seems to be a great option for those using blue-sensitive papers, and not very effective at all for anything that's green-sensitive. However, rubylith seems to be doing well in that latter capacity and from a few discussions I've had with people that know the material far better than me, I'm not worried about failure/fade at this point in time; it seems to have a good track record as an effective safelight filter for the sodium spectrum.

    I still haven't managed a better safelight test than my makeshift eight-minute coin check, but I did leave the light on for several hours straight last night in order to see how warm it got; the result was that the filter area was only lukewarm, but the lower part of the housing near the ballast was radiating a good deal of heat...so it appears that the ballast is the warm part on the light. I'm not sure if that's normal or not, but it was noticeably hot so I might consider putting a finned heat sink on the thing just to keep it cooled down a bit. Anyone else have any sort of significant heat from the ballast area?

  7. #47

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    Pictured: Approximate color with a rubylith filter.




    Apologies for the horrid cell-phone pictures; I had to play with the settings to get it to record something that approximates the real-life view and it generated a lot of noise in the image. Those problems aside, it's easy to see that this is a MASSIVE amount of light; one can easily read labels and see across the room.

    Pictured: Pay no attention to the clutter in the background.




    Snapping these two images was kind of entertaining because I could see WAY better than my phone's camera could see; the room is actually a lot brighter than the image implies and the printing on the Sprint bottle isn't nearly that blotchy. Ahh, the wonders of high-ISO digital photography...

  8. #48

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    Quick Update: I had a marathon printing session today that started with a couple of long paper tests; the long story made short is that I didn't have fogging or issues with highlights in any way, even after 30+ minutes under the safelight. The rubylith seems to cut the over-bright sodium lamp down to a very nice level and I printed all night with the vanes wide open. Seems that I've gotten this particular issue solved! Thanks to everyone for all their help and suggestions!

  9. #49
    Ken Nadvornick's Avatar
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    That's great to hear.

    Given that APUG is such a valuable database for searching, perhaps when you get a chance you could expand on your comments just a bit and give an explicit full description of your solution?

    For example, did you use only Rubylith filtration? Or was Rubylith in addition to other filters? If so, which ones? What positions? How many layers of Rubylith? Sandwiched between glass? Pre-threshold fog testing? Paper brands that did not fog? Distance of test papers from safelight? Etc., etc.?

    It's virtually certain that someone else down the road will find this thread and read those explicit answers and want to give it a try themselves...

    I'm still planning on more testing myself once I get my hands on some of those alternative filter materials. Unfortunately right now I'm planning for a cross-state large format photo vacation for October before the weather turns ugly again for ten months. So for the moment this is on hold.

    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

  10. #50

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    Quote Originally Posted by Ken Nadvornick View Post
    Given that APUG is such a valuable database for searching, perhaps when you get a chance you could expand on your comments just a bit and give an explicit full description of your solution?
    That's a good idea. I'll spell it out very clearly, then: There are two issues at play with the Thomas; light leaks and improper filtration...and to get good performance out of the light, both issues need to be resolved.

    One must first realize that due to the manner in which the Thomas is built - folded sheet metal that's riveted together - the gaps and seams in the safelight housing itself are a likely source for the unintentional escape of unfiltered sodium light; one must also realize that even a small amount of this light can be problematic because of the sheer intensity of the lamp. With that in mind, my advice is very simple: tape over every seam on the housing right out of the gate and thus negate the possibility of errant light escaping. A cleaner solution would be to take the housing apart and install some light-blocking foam or baffling of some sort wherever it's needed (which is almost everywhere) or to caulk over the seams with black silicone, but an effective on-the-cheap fix is any sort of opaque black tape. In addition to all of the seams on the housing, the interior corners of the lower filter "trays" - and if you have one of these lights you know exactly what I'm talking about - need to be taped/blocked, and the lower filters themselves won't be hurt by being taped into place, either. I'll restate it again for emphasis: TAPE OVER EVERY SEAM OR GAP.

    The second issue is filtration, and without re-hashing everything we've covered so far, I'll simply give you my final filter construction: one (1) sheet of rubylith sandwiched between the stock filter glass panels, with the edges taped as per a factory filter. There are no additional filters employed, and no diffusion material of any sort. There are no additional filters in the vanes; instead, a matte black board can be installed in order to dim the light as needed (such as when composing on the easel). The rubylith filter cuts the light output of the sodium lamp down quite a bit, but it's still quite formidable; thus, those that use faster papers or whom prefer less overall illumination may find that installing a black panel in the vanes greatly aids in controlling the ambient light level. I have found that I prefer the wide-open setting, but that's personal preference.

    At this point, the longest paper test I've conducted is 32 minutes on Oriental Seagull VC-FBII, and I noticed no fogging or burning on either pre-flashed or virgin paper; needless to say, this is FAR longer than is required for...well, almost anything. The approximate distance at which the test was conducted was 4 feet, with the vanes at their maximum opening. I can't speak for papers other than Seagull, but since this has been my most problematic paper in relation to safelights - it tends to fog/burn the quickest - I can only assume that most other papers would be safe under the rubylith filtration as well.

    That's all I can come up with, for now, but as I recall other important details - and I'm sure that I will - I'll add/edit as needed.

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