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  1. #41
    Roger Cole's Avatar
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    Quote Originally Posted by Michael R 1974 View Post
    Roger, for an extra few $ you can also put a dimmer on it (also from SuperBrightLEDs). It's a "pulse width modulation" dimmer so that there is no change in output spectrum. It's a no-brainer to hook up.

    Attached is the "Mark I" I made. I've since replaced it with a safer version, which is similar but larger and with a slot to insert #1 and #2 Kodak safelight filters. With that setup I get safe times way longer than I'd ever need, and it works great for making masks with ortho films (the reason I went down this path in the first place). The dimmer makes it really flexible.

    While safelights are everywhere, good ones are not, and just because something's expensive doesn't mean it's any good either.
    Depends on what you mean by "a good one." All those rectangular ones take standard filters and in my experience are very safe. So is my Patterson and I presume the same design labeled Arista and the newer different shaped Patterson.

    But if you mean some are not safe, true enough - like that Yankee with the white body and the two filters, one of which is not safe at least for VC. Granted it's labeled for graded but the VC filter is so un-necessarily dim it tempts one to try the graded filter.

    What you will get with LEDs is, probably (I'm going to verify this with mine of course) more light while still being safe, along with longer life and less fragility. That doesn't mean the others don't work fine.

    Still wondering if anyone has had any problem switching the LEDs with relay based timers. I'm going to try it anyway. If it fries them I'll eitehr go back to my regular ones until I can work out some noise suppression to isolate them more or just leave them on during exposure. I got used to that when I used my Duka regularly for B&W anyway.

  2. #42

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    You know what's intriguing about this, is the blue and green bulbs. Should these bulb's spectrum be compatible with VC paper emulsions it's a short leap to building your own additive VC lamp house for your enlarger.

    Steve

  3. #43
    Roger Cole's Avatar
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    I think that's been tried already, not sure how successfully.

    I have an LED white light lamphouse for my D2. It works beautifully with normal VC filters so the spectrum is pretty consistent with the original PH211. It has the bonuses of almost no heat with no negative popping and very long life. I bought it from a gentleman who makes them and posted them for sale on here and the LFPF. I don't know if he's worked on the VC head idea or not.

  4. #44

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    Quote Originally Posted by Roger Cole View Post
    Depends on what you mean by "a good one." All those rectangular ones take standard filters and in my experience are very safe. So is my Patterson and I presume the same design labeled Arista and the newer different shaped Patterson.

    But if you mean some are not safe, true enough - like that Yankee with the white body and the two filters, one of which is not safe at least for VC. Granted it's labeled for graded but the VC filter is so un-necessarily dim it tempts one to try the graded filter.

    What you will get with LEDs is, probably (I'm going to verify this with mine of course) more light while still being safe, along with longer life and less fragility. That doesn't mean the others don't work fine.

    Still wondering if anyone has had any problem switching the LEDs with relay based timers. I'm going to try it anyway. If it fries them I'll eitehr go back to my regular ones until I can work out some noise suppression to isolate them more or just leave them on during exposure. I got used to that when I used my Duka regularly for B&W anyway.
    Yes what I meant is that not all safelights are safe, particularly if one is working with film. That's all I meant.

    Regarding getting more light with LEDs, I don't know if that is the case or not, nor was it the reason I tried them. This of course would depend on the spectrum emitted, and the LEDs I used are not the sharpest cutting around.

  5. #45
    Roger Cole's Avatar
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    Film yes, very different.

    Another reason, if you can find them with the right emission line, would be more useful RA4 safelights. You can use the conventional ones as PE has posted but they need to be VERY dim (that said, just seeing outlines is VERY useful.) My Duka on lowest setting bounced off the ceiling is safe for brief exposure for RA4 and about as bright as a conventional Kodak OC black and white, but they are no longer available new. (Which is why I don't use mine for black and white.)

    The reason I am trying them is just to see if they are brighter than my regular safelights (well, one "regular" and a Jobo Maxilux which can still be found used from time to time) while being as safe. It's a fairly cheap experiment and if I don't want to keep them I can probably unload them here for less than I paid and cut the cost even more.

  6. #46
    Leigh B's Avatar
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    Quote Originally Posted by Roger Cole View Post
    if you can find them with the right emission line, would be more useful RA4 safelights.
    There's a disconnect here.

    Even if you can find an LED or similar emitter that's highly monochromatic, i.e. a single spectral line...

    the response curve of the film is not well-delimited, with significant sensitivity throughout the visible spectrum,
    even though the sensitivity peaks are well-delineated.

    With that type of film, no safelight can be completely safe.

    - Leigh
    “Wise men talk because they have something to say; fools, because they have to say something.” - Plato

  7. #47
    Roger Cole's Avatar
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    Quote Originally Posted by Leigh B View Post
    There's a disconnect here.

    Even if you can find an LED or similar emitter that's highly monochromatic, i.e. a single spectral line...

    the response curve of the film is not well-delimited, with significant sensitivity throughout the visible spectrum,
    even though the sensitivity peaks are well-delineated.

    With that type of film, no safelight can be completely safe.

    - Leigh
    There certainly is a disconnect. Who the heck is talking about film? Ok, I know the prior poster was, but I think about ortho film which certainly is safe exposed to red, if the red is narrow filtered and any other colors sufficiently low level.

    I know that RA4 paper is sensitive to all colors. But I also know it's less sensitive in some places. I think, but do not know, that this corresponds to the color of the orange dye masking layer. At least that looks very close to the color of my Duka 50 sodium, which again I have tested and shown to be safe for RA4, at least for 5 minutes exposure, when set on the lowest setting and bounced off my white ceiling in my old darkroom, with my particular set up. PE has posted about using the conventional #13 I believe, dark amber filter with RA4 successfully. Very dim, but better than nothing, and safe used properly. My reference to LEDs would mean that you need a similar emission - perhaps something slightly different would work even better.

    There is also this, but it's more for a flashlight (aka torch on that side of the pond) for looking into nooks and crannies, dropped items etc.

    http://www.rhdesigns.co.uk/darkroom/html/safetorch.html

  8. #48
    Leigh B's Avatar
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    I have film on the brain. Lots of threads going on here and LFPF about film processing.

    My comments apply equally to color paper. You can find spectral regions of reduced sensitivity, but not zero.

    - Leigh
    “Wise men talk because they have something to say; fools, because they have to say something.” - Plato

  9. #49
    Roger Cole's Avatar
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    Not zero true but low enough that a useful safelight is possible.

  10. #50
    Ken Nadvornick's Avatar
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    Quote Originally Posted by Leigh B View Post
    For example, quoting from a report entitled "SPECTRAL SIGNATURES OF NIGHTTIME LIGHTS":
    "High and low pressure sodium vapor lamps have very little variability. Both have strong emission
    lines at 819 nm. The low pressure sodium lamp has only one additional emission line of any
    consequence, at 589 nm.
    " (emphasis mine)
    Hi Leigh,

    Real world observations always trump theory. So I went down to my darkroom and fired up my Thomas Duplex and let it stablize. It has a reasonably low mileage tube. I removed all filters so I could see the bare bulb. Then I located my copy of The Hunt for Red October. (Appropriate for safelight testing?) I held up the DVD at an oblique angle to the bulb and observed with my own eyes the color bands generated tangentially to the recording tracks. This happened about 15 minutes ago.

    In addition to the overwhelming sodium D-line I was also able to easily make out additional blue, green and red bands. These corresponded very closely in both color and relative brightness levels to the three non-sodium emission spectra documented in Brian Niece's LPS discharge tube image and graph. The blue was very deep and the faintest of the three. The red was a bit brighter, but not nearly as bright as the green. But all three were unmistakable.

    I then refitted the Roscoe #19 Fire filter and looked again. As expected, the blue and green bands had disappeared, but the red was still visible. In other words, the Duplex was now converted into a truly safe light.

    If you look at the transmission chart at the above Roscoe link you'll see that in addition to cutting off the shorter wavelengths the #19 also transmits only about 35% of the sodium orange light. This also appeared to correspond visually with what I was seeing.

    Where do the additional emissions come from? I'm still speculating from impurities introduced inadvertently into the tube by the manufacturing process or materials, or on purpose as a consequence of the engineering required to create a commercially viable product. For example, this article describes the neon and argon Penning mixture added to LPS tubes to assist with the inital striking of the lamp.

    I would strongly suggest that you try the above first-person observation for yourself.

    Ken
    Last edited by Ken Nadvornick; 09-08-2012 at 02:18 AM. Click to view previous post history. Reason: Removal of incorrect conclusion...
    "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

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