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  1. #1

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    Unique Safelight Question (the effect of colored filters on red light)

    Hey There,

    I have a question about the effect of colored filters on red a red safelight. I used the word "unique" in the title so that people won't skip the post by thinking it's just another "will orange safelights fog "X" paper" type of question.

    My father has a talent for stained glass and has proposed that he make a stained glass safelight enclosure for my darkroom. First he planned to use only red and maybe very dark orange glass but then asked if he could use any color glass for the enclosure. His idea is that we could put both red and white bulbs in the enclosure along with a toggle switch or independent switches so that I could still view the art when the regular lights are on. He thinks that as long as the red bulb is the only bulb on the emitted light will be safe (the white bulb would be off when enlarging). I am unsure but my knowledge on this is next to nothing. I am hoping to get some clarification here.

    I'm basing my question on light charts like this (link). I understand that these charts are for the mixing of light and that my proposed safelight is different in that it would be a red light with filters (colored stained glass) used instead of actually mixing light that has already passed through a filter. Is there a difference? Will his idea work or am I rightful to question it? I know I could just try it out with scraps of colored glass held in front of a safelight-flashlight that I use but we live in different cities and I don't have any colored filters on hand to try it with. Thanks so much for any knowledge anyone can share. -Paul Cretini

  2. #2

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    A filter or coloured glass, whatever, cannot add any wavelengths that were not present as emitted by the original source. So if the bulb produces a colour that is safe, no filter can make it unsafe.

    If you have a red bulb that you determine to be safe (via a proper safelight test), you can put any colour around it you want, although note if the bulb is red and the glass is a complementary colour, not much light will come through at all.

    If you have a white bulb, then indeed the glass enclosure must be the correct colour to absorb (filter) the unsafe wavelengths. So you could only use the correct red or amber glass to make it safe for enlarging papers. Again, you'd have to do a proper safelight test.

  3. #3
    Truzi's Avatar
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    That is a really cool idea. I don't know much about safe bulbs, but I imagine there must be some bare red bulbs made specifically as safelights. I'm sure a Google search would bring them up.
    Truzi

  4. #4

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    The problem with most red light bulbs that I have seen is that the red coating does not go all the way to the lamp base. Any white light escaping from this area will cause fogging. You would have to cover this area in some way -- say black paint.
    A rock pile ceases to be a rock pile the moment a single man contemplates it, bearing within him the image of a cathedral.

    ~Antoine de Saint-Exupery

  5. #5
    AgX
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    Quote Originally Posted by Truzi View Post
    That is a really cool idea. I don't know much about safe bulbs, but I imagine there must be some bare red bulbs made specifically as safelights. I'm sure a Google search would bring them up.
    There was a range of bulbs with different coatings apt for the various spectral sensitizations of the materials.
    (Last year I even ruined one of those bulbs when I cleaned the dirty bulb be means of warm water, totally having forgotten that the coating was made from dyed gelatin.)

    Quote Originally Posted by Gerald C Koch View Post
    The problem with most red light bulbs that I have seen is that the red coating does not go all the way to the lamp base. Any white light escaping from this area will cause fogging. You would have to cover this area in some way -- say black paint.
    The lamps I know have a rubber sock where the bulb enters the metal capsule, to cover any uncoated parts of the bulb.

  6. #6

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    Stating the obvious, a red party-bulb isn't going to be paper safe. The low wattage darkroom bulbs are OK-ish, but may have different safe distances than whatever you use at the moment, so check as usual. As AgX pointed out, the darkroom bulbs are not quite the same construction as the usual cheap light-bulb, as they are better made to do a specific job.

    Different coloured glasses look different because they absorb the wavelengths which are not that colour. Better to say that what you see, in the light transmitted by the glass, is the group of wavelengths which are not absorbed by the dyes etc. in the glass.

    Did you ever read of portrait studios, a hundred years ago, painting all their windows blue, to try and somehow increase the amount of blue light for their blue-sensitive materials? It never worked

  7. #7
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    See: http://www.kodak.com/global/en/consu...cts/pdf/k4.pdf

    First, let me apologize in advance for any offense this may cause to the OP or any commenter, but this is an on-going debate.

    Please obtain, test, and use a proper safelight. There have been many threads on this forum over the years with similar things. There have been numerous augmentative posts. People will spend money on cameras, film, paper, chemistry, tanks, trays and enlargers, the best lenses, but won't buy a proper safelight. If your talented father wishes to make you a lamp, that's great; but you and he do not need to re-invent a critical piece of darkroom equipment that is readily available.

    From the Kodak pub cited above:

    ​IMPORTANT FACTS ABOUT SAFELIGHTS
    > No safelight provides completely safe exposure for an indefinite period of time.
    > Safelight filters are designed for specific types of paper and film.
    > Safelight filters fade with use.
    > Poor safelight conditions can produce a loss in photographic quality before actual fogging is visible.
    > Many photographic materials require handling in TOTAL darkness.

    Therefore, you should
    • Follow all safelight recommendations for your paper or film.
    See product instructions for recommended safelight filter, bulb wattage, and minimum safelight distance.
    • Test your safelight conditions regularly.
    • Replace your safelight filters when necessary.


    And as has already been mentioned, with any safelight, testing is necessary. The procedure is also outlined in this (and other) publications. Good luck!
    David
    Taking pictures is easy. Making photographs is hard.

    http://www.behance.net/silverdarkroom
    http://silverdarkroom.wordpress.com

  8. #8

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    Dear jeddy-3,

    What a terrible waste of a nice lamp tucked up inside a darkroom. ;-) While you can make it work, it would be far better to have your father make you a nice lamp you could use in your home, then spend some time photographing it.

    Good luck in whatever you decide,

    Neal Wydra

  9. #9

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    There are colored safelight bulbs, I have a couple.
    You also don't have many options on size. One of mine is small similar to a PH-140 enlarging bulb, the 2nd is HUGE like a G40 globe bulb.
    I see that Adorama has similar bulbs, and they are expensive, the small size is $17
    http://www.adorama.com/DKSLJ.html
    Given the bulb situation, I would just keep the stained glass out of the darkroom.

  10. #10
    Truzi's Avatar
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    If you do have this lamp built, I'd really like to see a few pictures posted.
    Truzi

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