Which size/type lightbulb behind red filter for a safelight?

Discussion in 'B&W: Film, Paper, Chemistry' started by Sirius Glass, Dec 29, 2007.

  1. Sirius Glass

    Sirius Glass Subscriber

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    I have converted my bathroom to a part-time darkroom. I removed the 75 watt bulb ceiling light that turns on with the fan. I am having a dark red piece of Plexiglas cut to fit into the ceiling fixture.

    Two questions:
    1. The Plexiglas that is being cut is not a safelight filter but it is very close to the color and density of the 8" x 10" safelight filter from FreeStyle. Is this good enough or will I have to have the safelight filter cut down?
    2. What should I replace the 75 watt bulb with: a 15 watt bulb, a 25 watt bulb or a CFL bulb [if so, what size?]? This fixture is not directly over the chemical trays, but it is about 4 to 6 feet away.
    Note: The plastic company does not want to cut plastic that they unfamiliar with. They are charging $6 for their plastic cut to size. If their "filter" does not work, then I think I can get them to cut the 8" x 10" filter down.

    Thoughts?

    Steve
     
  2. JBrunner

    JBrunner Moderator Staff Member

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    Easiest is to take a sheet of paper out in the dark, safeguard your paper stash, and then set the paper on your work area with an object on it, a few coins, or maybe a ceramic elephant. After a few minutes process the paper and see if you get an outline. That way you can experiment with different bulbs. The CFL is likely very high in blue and green outputs, but who knows? If the plex isn't red enough, you can add some red gel.
     
  3. Snapshot

    Snapshot Member

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    You can probably get away with the red plexiglass, although I would advise that you test it first. There are a number of ways to do so and you can find them using the APUG search tool. Replace your 75 watt bulb with a 15 watt bulb but not a CFL version.
     
  4. Sirius Glass

    Sirius Glass Subscriber

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    That is my plan, I was hoping someone here might have gone through this process.

    Thanks,

    Steve
     
  5. JBrunner

    JBrunner Moderator Staff Member

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    I have been through it, but there is no way to know if we are using the same stuff. After going through all the machinations on one light, I just purchases safelight bulbs for the other fixtures. ( Which are just the clip up spun aluminium lamps, my darkrooms pretty big)
     
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  6. Sirius Glass

    Sirius Glass Subscriber

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    My first thought was to buy a safelight bulb, but FreeStyle only had a tiny, dim bulb [7 watts]. The salesperson told me that the red coating would slowly melt off in the fixture canister. He also told me that the red bulbs sold in hardware stores were great for fogging paper.

    Steve
     
  7. Sirius Glass

    Sirius Glass Subscriber

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    Thanks, I will get one this afternoon.

    Steve
     
  8. CBG

    CBG Member

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    Another couple of thoughts, if you get a little fog but are most of the way there by using the red plastic. 1. put a deep red theatrical gel behind the red plastic, 2. replace the regular bulb with a red bulb in addition to your red plastic.

    Check www.rosco.com for gels, and any hardware store for colored lamps. Keep the wattage down regardless.

    Theatrical gels are pretty tough, designed to work with high powered stage lighting, but in a totally enclosed space you want to be very conservative about heat build up.

    C
     
  9. srs5694

    srs5694 Member

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    As JBrunner suggests, the only way to be sure if your safelight is safe is to do a test on it. This is true whether you use a "generic" red plastic filter, as you're attempting, or if you use a conventional safelight. Even "real" safelights can fog paper if they're the wrong type for your paper, if they're too close to the paper, or if the paper is exposed to the safelight for too long.

    In addition to the options you're considering, you might consider a red or amber LED bulb. You can find several at http://www.superbrightleds.com. I use one of their red E27-R24 bulbs as one of my two safelights, and it works well for me. This particular bulb screws into a normal Edison bulb base, so you don't need a special fixture.

    In theory, a CFL might work as a safelight, if it's properly filtered; however, CFL bulbs are generally designed to replace 60-120 watt tungsten bulbs, and so are likely to be too bright unless they're kept very far from your paper.
     
  10. John Koehrer

    John Koehrer Subscriber

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    That tiny 7W bulb puts out plenty of usable light in a small darkroom & I doubt that the coating will "melt" off. It may scratch off from handling. If it's a standard base it could be the easiest & simplest choice. Screw it into the socket & yer done.
     
  11. Stan160

    Stan160 Member

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    My uncle, who owns an electrical shop, ordered a 3W CFL lamp for me to try in a safelight. According to the packaging it is equivalent to a 15W conventional lamp.

    One safelight test coming up!

    Ian
     
  12. fschifano

    fschifano Member

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    Go to an art store and get some rubylith. The stuff is designed to be used as a mask for orthochromatically sensitized materials - just like B&W photo paper. I have made a couple of safelight filters using a couple of layers of this stuff sandwiched between a couple of pieces of glass cut to the proper dimension. Works just fine after a proper safelight test. Of course, as with any safelight, it's only safe when used with dim light bulbs.
     
  13. nworth

    nworth Subscriber

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    The lamp size for a safelight depends on a lot of things: the filter, the distance from the light to the material, whether the illumination is direct or reflected, even the lamp itself. With Kodak filters, Kodak usually recommends a 15 watt inside frosted incandescent lamp for direct illumination at four feet. But other safelights work differently. I have a safelight for VC papers that uses a 20 watt standard cool white fluorescent tube. That's a bright lamp, and the safelight is bright, but it is perfectly safe at four feet. You should go by the manufacturer's recommendation. If you can't find that, use the Kodak rules (which are fairly conservative) as a starting point; then test the safelight. The inverse square law applies, of course, and you can use an appropriately larger lamp at greater distances.

    I would stick with the better known commercial products. The plastic you mention for a home grown safelight _may_ work, but different plastics vary a lot in their transmission, depending on the plastic, the dyes used, and the manufacturing process. If you usiig it, be sure to do some thorough testing. One additional possibility is to use a red LED cluster. You can get these with a standard lamp base. They are quite bright and perfectly safe for printing.
     
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  14. Cruzingoose

    Cruzingoose Member

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    Safelights

    I gave up on red years ago, too harsh on the eyes. Since the advent of LED Christmas lights, I've found and have been using a set of yellow (35 light) string for several years now. Nice color that won't fog paper even after 10 minutes in the open. This would be the time to buy a set really cheep also. But since you have the red plexi already cut, pick up a pack of C-7 red or orange Christmas lite bulbs for 50 cents and a candleabra to edison base socket adapter and you've got safelights to go untill next Christmas.
     
  15. Sirius Glass

    Sirius Glass Subscriber

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    Good advise, except that I am asking about a ceiling light in a canister. The light goes on when the fan is turned on. Either I remove the bulb or I convert it into a darkroom light. A commercially available safelight will not work in this situation.

    Steve
     
  16. Sirius Glass

    Sirius Glass Subscriber

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    Follow up:
    The cut red plastic disk using the plastic store's red plastic did not work with a 25 watt or 15 watt bulb. Now the red plastic appeared to be almost the same color as the safelight filter I had brought [the plastic store did not want to cut it since they did not know the cutting characteristics of the filter]. I know that what the eye sees and what the paper sees are not the same thing. The problem could have been all the light leaks around the fixture cover.

    I ended up taking the plastic store filter out of the canister and returning the safelight filter. I purchased a red bulb from FreeStyle and that solved the problem.

    Thanks for all the suggestions. I used the "old quarter on the photographic paper for five minutes" to do the testing.

    Steve
     
  17. richard ide

    richard ide Subscriber

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    When doing the "coin test" Make an exposure on the paper with a negative without a safelight. Then place coins on the paper for varying lengths of time under the safelight. This way, the paper has received an overall exposure and will show small variations in exposure which may not show up the other way.