enlarging light source

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Was wondering if anyone had used a neon light as a cold light source for b&w printing? I know that Aristo uses a mercury vapour lamp in their cold light sources, but wanted to know how neon affects b&w papers? thanks

-- Colin Seaman (cbsea@hotmail.com), April 28, 1999


True neon (orange glow) wont expose paper at all. In fact, it's probably a fairly decent safelight. Mercury vapor lamps emit a high percentage of high energy UV and near-UV which is very effective in exposing photo materials. There used to be a line of contact printers used in the military photo labs for contact printing 9 inch aerial film that used a bank of Argon (blue glow) lamps in a grid containing maybe 25 lamps that could be switched on or off for local dodging. You cant mistake the machine -- they need four people to lift them.

-- tony brent (ajbrent@mich.com), April 28, 1999.

this particular neon lamp is very blue, much colder looking than say a daylight fluoresent tube. I have no idea what level of UV the lamp emits if any.

-- Colin Seaman (cbsea@hotmail.com), April 29, 1999.

Flourescent tubes use a number of different noble gasses wihich emit light when an electric current is passed through them. As mentioned above, neon gives off an orange red, argon gives a green light, etc., etc. The actual color of light you get depends on the flourescent coating of the tube you have. A fine coat of flourescent powder is applied to the inside of the tube which absorbs light of one color and emits light of another. Manufacturers mix and match flourescent materials to come up with many different combinations for different purposes and tastes. These tubes do not emit a continuous spectrum so a color temperature meter will not give you any usefull information. You could write the manufacturer, of find someone with the necessary diffraction measuring equipment, or just experimen. Of course, if you ever change tubes, the characterstics will probably be different. Since most B&W emulsions can be exposed with blue and blue-green light, any light source with these characteristics will work. Time and, with variable contrast papers, filtration will vary according to actual spectral composition and intensity. Regards, ;^D>

-- Doremus Scudder (ScudderLandreth@compuserve.com), April 30, 1999.

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