can fluorescent lights fog film?greenspun.com : LUSENET : Large format photography : One Thread
can fluorescent lights fog film even if they have not been turned on? i seem to be fogging film in a dark area, even though i don't turn on the lights. this is driving me crazy! does anyone have any experience with this problem?
-- howard b. schwartz (email@example.com), November 30, 2001
Fluorescent lights can indeed fog film, even if they haven't been turned on. The phosphur used in flourescent tubes can remain charged either by a bright light source, or just after having been turned off. You can prove this to yourself by turning them on then off and sitting in the dark room for 5 minutes. After your eyes become adjusted to the dark, look at the lights and you will see them glowing. Remove the flourescent lights from your darkroom and be worry free.
-- Pete Caluori (firstname.lastname@example.org), November 30, 2001.
Hi Howard, funny you should bring up the subject. I've been loading holders in my bathroom, with a fluorescent light, and then it dawns on me that even though I've turned the light off - sometimes it doesn't totally go out. Good luck, David
-- david clark (email@example.com), November 30, 2001.
It's true that the tubes glow for a while after they have been switched off, but if the films remain at some distance and don't stay in the open for too long, I don't think this is enough to really produce a noticeable fogging. However, if the place where you load your films is close to the tube, you should perhaps remove it.
-- Paul Schilliger (firstname.lastname@example.org), December 01, 2001.
Just to confirm the others, it's been in the literature for decades that film can be fogged by the afterglow of flourescent tubes. I've never documented it personally, but maybe you just have.
-- Carl Weese (email@example.com), December 01, 2001.
I recently replaced my flourescents in my darkroom with new flourescent bulbs with a high CRI of 98. After loading osme film holders one day, I was alarmed to notice the afterglow others have mentioned. I decided to test. I left several unexposed sheets of TMX on a white table about three and half feet directly below the bulbs for five minutes just after turning off the lights, and then developed and processed them normally. The sheets were absolutely clear indicating no fogging. I don't think it's a problem.
-- David Kaufman (firstname.lastname@example.org), December 01, 2001.
Some Kodak publication I remember reading years ago, probably the Darkroom Guide, said that you should wait ten minutes after turning off a fluorescent light before opening film. It may be an excess of caution but I've been waiting those ten minutes for years and haven't had a film fogging problem.
-- Brian Ellis (email@example.com), December 04, 2001.
Howard: To prevent problems have available incandescent lights as well as fluorescents. The fluorescents are essential for viewing colour, assuming of course that you use fluorescents with the proper spectrum. Several manufacturers make those but you will not find those at Home Depot. Before handling sensitive material I would wait at least ten minutes after the fluorescents have been turned off. Some phosphors seem to keep on glowing for a very long time. Beware!
-- Julio Fernandez (firstname.lastname@example.org), December 04, 2001.
The darkroom I use has fluorescent tubes which cause a 5-10cc shift towards yellow in most RA4 papers even after being off for ten to fifteen minutes. I have never bothered to see if they fog film because I'm sure they will. I use a desklamp with a conventional tungsten bulb in it while printing.
How bad the problem is depends on the phosphor coating in the tubes you use and on how long the lamps were lit before being turned off. The simplest way to check is to do a standard safelight test and look for changes in a sheet of film flashed to a mid-tone density and then partially exposed to the fluorescents.
-- Struan Gray (email@example.com), December 05, 2001.