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  1. #31
    Leigh B's Avatar
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    Quote Originally Posted by dpurdy View Post
    The Thomas makes a lot of noise.
    Then it's broken and needs to be fixed. Mine makes absolutely no noise.

    I have encountered other posts where users report noise.

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

  2. #32
    Ken Nadvornick's Avatar
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    Quote Originally Posted by Leigh B View Post
    Could you explain the mechanism, please. Sodium is monochromatic (two closely-adjacent spikes).
    Yes, but I believe that there is more than just sodium contained within an LPS tube. This is from memory, but I believe there is some neon and argon in there as well? Perhaps other stuff also? I know that the HPS lamps show a far larger number of more intense blue spikes due to the presence of mercury in those tubes.

    So I'm assuming, but do not know for a fact, that the additional emission spikes are impurity-related, intentional or otherwise. If somone knows more about this, please ring in. I'd love to hear more.

    In any case, take a look at this link by Brian Niece, Associate Professor of Chemistry at Assumption College in Massachusetts. It details some of his real-world classroom lab results of capturing various emission spectra. His recording of the emissions from an LPS discharge tube are shown in the 4th example down the page. (The photos and graphs will all enlarge if you click on them.)

    Note the third photo. It distinctly records the non-doublet spikes on both sides of the primary D-line emission. Those green and blue spikes are the ones I'm referring to. They are far weaker than the doublet, but are nevertheless present.

    Given that after I applied the Roscoe #19 Fire filter (with no other changes to the system) my bromide paper fogging essentially vanished, I'm concluding those types of spikes were the culprits.

    Ken
    "Hate is an adolescent term used to stop discussion with people you disagree with. You can do better than that."
    —'blanksy', December 13, 2013

  3. #33
    Leigh B's Avatar
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    Hi Ken,

    Assuming the report is as you stated (I did not read it), I can find no other source online to substantiate it.

    All of the other reports from various government agencies show only the Na line at 589nm and an IR line at 819nm (much reduced).

    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)

    Here's a spectrum for the SOX bulb from a company that makes them:
    Click image for larger version. 

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    - Leigh

    Ref:
    SPECTRAL SIGNATURES OF NIGHTTIME LIGHTS, Christopher D. Elvidge
    NOAA National Geophysical Data Center, Boulder, Colorado USA

    Abstract
    A spectral library is being built for a wide range of lighting types.

    URL: http://www.asdi.com/getmedia/05be995...IGHTS.pdf.aspx
    Last edited by Leigh B; 09-07-2012 at 01:54 AM. Click to view previous post history.
    “Wise men talk because they have something to say; fools, because they have to say something.” - Plato

  4. #34
    Mark Fisher's Avatar
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    LEDs can be quite safe and much brighter....and inexpensive. Why would anyone use a traditional safelight (:
    Your first 10,000 pictures are the worst - HCB

    www.markjamesfisher.com

  5. #35
    David Brown's Avatar
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    Quote Originally Posted by Mark Fisher View Post
    LEDs can be quite safe and much brighter....and inexpensive. Why would anyone use a traditional safelight (:
    Good question ...

  6. #36
    Michel Hardy-Vallée's Avatar
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    Quote Originally Posted by David Brown View Post
    There have been numerous threads on this forum over the years with similar things. People will spend money on cameras, film, paper, chemistry, tanks, trays and enlargers, and then want the best lenses, but won't buy a proper safelight. Seriously, they aren't rare. What is the deal?

    There is also the LED school. I understand and appreciate the fact the the right LEDs will work, but I perceive that many folks end up spending as much on obtaining and testing the correct LEDs as they would have on just getting a real safelight. Safelights can be had used, just like the enlargers, lenses, tanks, trays, etc.
    Yes, safelights are rare.

    I live in a major metropolitan city and I can't find anymore the large orange globe model I used to have, only tiny dark red ones, which are hard on the eyes for nothing when you're printing on graded paper.

    Like every incandescent bulb, they burn. In addition, unlike LEDs, a few knocks when the lamp is stil warm, and the filament is bust. When you have a makeshift darkroom that you must tear down every time you're done, things get shuffled around.

    LEDs have a gazillion-hours life expectancy, and are not sensitive to knocks. Plus, when you buy from a decent supplier, you get a spectrum graph that you can match with your papers.

    I now have an exceedingly bright and clear amber light that works even with VC, and makes B&W printing as easy on the eyes as working with white light, and a red one for when I need to work with ortho materials.

    I got two of each (something everybody should do, no matter what kind of safelight you're using), so that whenever the first one breaks, I have a spare.
    Using film since before it was hip.


    "One of the most singular characters of the hyposulphites, is the property their solutions possess of dissolving muriate of silver and retaining it in considerable quantity in permanent solution" — Sir John Frederick William Herschel, "On the Hyposulphurous Acid and its Compounds." The Edinburgh Philosophical Journal, Vol. 1 (8 Jan. 1819): 8-29. p. 11

    My APUG Portfolio

  7. #37
    Roger Cole's Avatar
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    My order from SuperBrightLEDs arrived yesterday. I should have time to play with them this weekend. I'll get back to you on whether they're brighter while being just as safe (the reason I decided to try them.)

    But safelights are far from rare. If you only look locally than many things are rare, including film other than 35mm consumer C41 and even that can be rare. A quick check on Freestyle turns up their Arista brand in both OC and red (looks identical to my older Patterson, uses common as dirt 7W bulbs available in packs of four for a few bucks at Home Depot as well as other places or online) and Premier models with interchangeable filters in both 5x7 and 10x12, plus the sleeves that go over fluorescent tubes (no idea how safe those are though - not very convenient unless the tube fixtures are already there) and bulbs and filters for the Thomas.

    B&H has a selection of Arkays, Dorans, Patterson (a different shape than my older one,) Yankee (careful with that one - I had one of those years ago with a black body which was fine, and then later a white one which was NOT fine, at least not with the standard filter. Very bright and lots of fog. It comes with a VC filter too but if you get it used you may not know that. The VC filter is fine but gives up all the brightness advantage of the white reflector body) and various colored simple bulbs.

    eBay or the various photo forums will turn up others quite easily.

    Use LEDs because they're brighter and safe and durable, or because they're cheap. But safelights designed as such are anything but rare. They're as readily available as paper and developer.

  8. #38

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    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.
    Attached Thumbnails Attached Thumbnails Red1.JPG   Red2.JPG   Red3.JPG  

  9. #39
    Sirius Glass's Avatar
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    Sometimes there no limiting bounds on stupidity.
    Warning!! Handling a Hasselblad can be harmful to your financial well being!

    Nothing beats a great piece of glass!

    I leave the digital work for the urologists and proctologists.

  10. #40

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    I meant only to give Roger some ideas since he wanted to try LEDs. And this simple DIY safelight, which works very well, was also cheap - perhaps a worthwhile alternative to someone on a budget. Apologies for posting.

    Also, people posting to call someone else stupid should probably at least make sure the post is grammatically sound. Otherwise some weight is lost.
    Last edited by Michael R 1974; 09-07-2012 at 05:57 PM. Click to view previous post history.

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