At 3:39 AM +0000 2/27/03, olympus-digest wrote:
>Date: Wed, 26 Feb 2003 19:18:12 -0800
>From: Winsor Crosby <wincros@xxxxxxxxxxxxx>
>Subject: Re: [OM] Humidity and fungus growth on optics and film
>
>On Wednesday, February 26, 2003, at 06:58 PM, Joe Gwinn wrote:
>
> > Basically, fungus won't grow below 40% RH, but below 30% RH, static
> > electricity becomes a big problem, so the target range is 30% to 40%
> > RH.
>
>Why is static electricity a big problem for storage of lenses or
>already developed film? Having lived most of my life in an area where
>low humidity and static electricity occurs fairly frequently it has
>never been a problem storing things.
I was summarizing the statements of manufacturers that make humidity-control
cabinets for industrial use. The issue is electrostatic discharge (ESD)
causing damage to unpackaged electronics. I should have made that clear.
Components that will be wave soldered are dried to less than 5% RH, so the heat
doesn't cause trapped moisture to burst out, damaging the component.
For a mechanical camera, even zero RH would be no problem, although the grease
may dry out slightly faster. The big issue is that the electrostatic capacity
of the human body is substantial, and considerable electrical energy can be
delivered to an unprotected electronic component, destroying it. For a camera
with electronics, like an OM-4, it's a theoretical problem, but probably not a
practical problem as such devices are always designed to tolerate considerable
ESD. Nor can I recall any stories of people shuffling across the living-room
rug in the winter, and destroying their wunderbrick upon picking it up.
Considering the prevalence of ESD in the world, we would have heard of this by
now were it a real problem.
Joe Gwinn
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