Building a Sodium Vapour Safelight

[Vlad Soare]

Hi guys,

I can find locally small sodium vapour lamps and ballasts much cheaper than Thomas safelights and their corresponding bulbs (especially as these must be bought from abroad, and shipping isn't cheap either). I was wondering if there's more to a Thomas safelight than the lamp itself. Is it just a regular sodium vapour bulb with two flaps to control the light output? Or is there more than meets the eye?
Could I just buy a regular sodium lamp, a starter, a ballast, and improvise some baffles to reduce the light output to a safe level? Will this get me something similar to a Thomas safelight?
I believe all sodium vapour bulbs emit light in a very narrow yellow band, so it's not like they made a special paper-safe bulb for the Thomas, is it? :confused:

Thank you.

[Peter De Smidt]

The Thomas safelights are very bright, but I've heard from people I trust that they can fog some of today's VC papers. If you want a do it yourself safelight, you might investigate red LEDs.

[Bob Salomon]

I can't tell you about the Thomas but I can give you the specs on the Osram/Kaiser Duka 50 sodium vapor safelight. It used an Osram sodium vapor lamp NA 10 FL.
The NA FL 10 lamp (no longer manufacured) was a 10w lamp specially made for darkroom use. It deliverd a perfectly vertical straight spectral responce at about 590nm.

Color papers were insensitive to light between 570 and 610nm. The Duka 50 also was packaged with a filter for use when using VC papers (Kaiser and Osram based their VC specs on Ilford papers).

So in this case yes, a special photo only sodium vapor lamp was made by Osram for the original Duka 10 and the later Duka 50 models that were made by Kaiser for Osram and later were sold only by Kaiser.

The Osram bulb number for this lamp was 83977.

And this safelight could be used for either direct or indirect illumination. It was not made to be suspended from the ceiling but could be wall mounted or used on a flat surface.

[W K Longcor]

I have used te Thomas lights in darkrooms for years. They are great. Wide open, you can comforatably read your daily newspaper. Common sense might tell you this is too bright for usual daarkroom work ( it overpowers the image on the easel so yyou can't see it t focus). The main body of the light has two yellow "filters" that cut down the light a bit. Then, the flaps have further "red" filters that can be used. For almost all modern vc papers, I used the flaps with the standard red filters in them and had the flap just a bit open. This gave a very comfortable working environment and never caused any fogging of any paper I used. If you are using something even more light sensitive just close the flap all ther way and you still have plenty of working light. With the flaps fully closed, you can work with most ortho materials ( litho films, etc.) with no problems. There was also a set of dark filters for the flaps that when fully closed, would allow a suprisingly bright darkroom environment for color print materials (papers for printing from color negs). Unlike many darkrooms, my ceilings were all painted white ( except right over the enlarger). With the Thomas light, the entire ceiling was illuminated. As a result there was never any eye strain (OK maybe at three AM pushing out a rush job, but that's not the fault of the light).

Remember, the design of the Thomas light is for hanging above -- no direct light hits the work area --all light is from the reflection from the ceiling. I used Thomas lights for almost 30 years --NEVER had any fogging problems IF USED PROPERLY.
Hope this explanation helps you with your building project.

[Brian C. Miller]

Go to DigiKey.com, and do a search for "orange yellow led" (without the quotes) and the discrete parts show what wavelength they emit. There are LEDs with 592nm output.

[Peter De Smidt]

Whatever safe light one uses, make sure to do the Kodak safe light test with each type of paper you have. Loss of contrast is more insidious than fogging of the paper base.

[Henry Ambrose]

Go to DigiKey.com, and do a search for "orange yellow led" (without the quotes) and the discrete parts show what wavelength they emit. There are LEDs with 592nm output.

LEDs are vastly superior to a Thomas and they are silent.
The hum of a Thomas drives me crazy.
You can have a darkroom that you can read a newspaper in using LED safelights.
I do and I love it.

I use some like these:

http://www.optiled.com/ProductDetail.aspx?id=eab52be7-5c09-48d8-a808-2e2f70607eb1&CountryId=30b3c7ef-48e8-4a1d-b344-2506b594499e

(not exactly the ones I have)

[Vlad Soare]

I see.
The LED idea sounds great, too. I'll investigate this option, as it seems to be simpler and more convenient than sodium lamps.

Thank you.

[Vlad Soare]

Henry, do you happen to have a link to the precise model you're using?
I find that not all LEDs are really monochromatic. Red Osram bulbs, for instance, show a small amount of green (or is it blue? It's hard to tell) if you look at a CD sideways. And they do fog my variable contrast paper if they're too close - I've tried it.
I'd like to try out the bulbs that you're actually using (if you're really happy with them, that is).
Thanks.

[Henry Ambrose]

Vlad,

They no longer make the ones I have. Look at the link I supplied above, it is the closest thing I found to what I use, same company but different model. They specify the wavelength of light emitted by each color. Amber or red will work for darkrooms.

If you consider other led lamps ask for the "spectral distribution" information to make your decision.

[chris_4622]

http://borealislighting.com/decorativelighting.html

I use the M60 in red.

[Eric Woodbury]

I've heard that some sodium lights will fog some papers also. I've taken all the conventional safelights out of my darkroom and replaced them with LED lamps such as these in either amber or red

http://www.superbrightleds.com/cgi-bin/store/index.cgi?action=DispPage&category=MR16&Page2Disp=%2Fspecs%2Fe27-w8.htm

I put these in a small clamp on fixtures from Home Dump. Over the wet side I have a string of red LED Christmas lights. It is bright. All those lights run on less than 15W. I like that in the summer.

[Henry Ambrose]

Here's the technical info from the link I gave:

[BetterSense]

I have homemade red LED safelights. They draw so little power that I often just leave them on 24/7. Nice and bright and perfectly safe.

[Habanero]

I have a Duka 10 Safelight and i don't need it. Going totally digital these days..

Come over for a cup of coffee and it is yours :)

Among other stuff i also have a Durst M305 color, haven't used these toys since the 90's...

Location, Sweden.

[Jay DeFehr]

I bought a red fluorescent spiral bulb for $4, and it lights my dark room so well I was sure it wouldn't be safe, but it is. This little light has completely changed my printing experience.