Re: Gralab Timer & HIE 4x5 Sheet Film

[boblong@xxxxxxxxxxx (Robert Long)]

On Mon, 30 Dec 1996 20:29:01 +0000 (GMT), you wrote:

|give off if any?  I was told that it actually does not give off any =
light=20
|at all (I find this hard to believe since I see the glow of the timer of=
=20
|the walls of my darkroom) but gives off a glow from absorbed light.  =
When=20

Sounds as though someone was confusing phosphorescence (the Graylab's
way of generating light) with fluorescence--the ability to absorb
invisible ultraviolet and convert the absorbed energy into visible
light in real time.  Phosphorescent materials do absorb energy and
re-emit it, but only gradually, so you your Graylab will glow after
the lights are turned off.  But the fact that you can see its glow
means that it is producing light, q.e.d.  It is a greenish light,
which means that it perhaps looks slightly brighter to the human
retina than it does to films, but the difference presumably is
negligible.

When I used a darkroom with a Graylab and I was working with a film I
was nervous about, I used to either sit with my back to the timer and
work on the far surface or turn the timer to face the wall, like a
naughty child.  I didn't have fogged films, but I never proved to my
own satisfaction that they wouldn't have remained unfogged without the
precautions.

Bob Long
(boblong@xxxxxxxxxxx)

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Topic No. 5