Archived posting to the Leica Users Group, 2001/07/30
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]At 12:00 AM 7/31/01 +0200, you wrote: >Tina writes: > > > Fluorescent lights can continue to fog film > > even after they've been turned off. > >Really? How? I've always heard this. A quick search on google turns up this: "Technically, the afterglow is phosphorescence, not fluorescence, but the effect on your film is the same. There are no general rules: there are many different tubes out there, and they all have different afterglows. In the darkroom I use, the ceiling fixtures will noticeably fog RA4 paper up to quarter of an hour after they are turned off. A standard darkroom safelight test will tell you if your fixture is causing a problem. The afterglow usually has blue or even ultra-violet components, so even ortho-lith film can be fogged. On my RA4 paper tests the 'fogging' showed up as a 5-10cc shift to yellow, rather than a noticeable darkening of the print. " and from the Kodak site: "Never have fluorescent lamps in the darkroom! Fluorescent lamps remain glowing after the power is turned off and will cause film fog." Tina Tina Manley, ASMP http://www.tinamanley.com