Re: "blacklight" tubes and light sources in general

>>> mkochsch@shaw.ca 02/14/05 10:42 AM >>>
The lore is that fluorescent bulbs keep glowing/emitting long after
they've
been turned off. I have a fluorescent fixture in my darkroom which I
shutoff
at least 10-20 minutes prior to working on any film. Could the fogging
be
caused by leaving the contact frame in the UV box and going for coffee?

Nope.

I've done some careful testing, balancing and critically evaluating the
exposure using the two UV sources on the same emulsion. If the fog is
related to lamp fluorescence when the power is off, or warmup/cooldown
of the tubes, etc., that is not something I care to try and
discern/control. I've wasted enough paper in the past to this effect.
Simply switching lamp types solved the problem (permanently as far as I
can tell). Why go back and try fit the other into some procedure that
MAY work when I've evolved a procedure that DOES work, for me, every
time?

I've been in enough discussions with others to know that some don't have
this problem and others do. What I would suggest is that if someone is
having exposure variation or fogging with the UV tubes, that they switch
lamp sources and determine whether the quartz or metal halides work more
consistently for them. I certainly don't expect anyone to switch just
because I have better results with halogen sources, but I'm not going to
recommend something to a novice that I know from experience may cause a
problem. There are so many bad recommendations out there in various
sources that a beginner may be having a problem, doing everything by the
book, and still getting inexplicably poor results. If I can help
someone avoid that, I'm happy to do so. I've found the UV tubes to be a
potential source of an exposure problem (with gum bichromate only) and
so I'm passing along that experience and recommendation FWIW.

"If it ain't broke, don't fix it" but also "if you keep doing the same
thing and expecting a different result, that's crazy."

YMMV.

Joe
Received on Mon Feb 14 11:03:53 2005