Archived posting to the Leica Users Group, 2006/05/26
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>
>In a message dated 5/26/2006 1:10:57 P.M. Central Daylight Time,
>henningw@archiphoto.com writes:
>
>It just responds to ambient radiation to
>such an extent that it will fog even when cold. Don't try to use
>ISO800 or higher colour film more than a year past its expiry date,
>even when frozen.
>
>
>
>Can you shield it from radiation easily?
Lead bags _might_ give you another year, but I wouldn't trust it.
Film grains have a certain latency w.r.t.
radiation, of whatever form. This is based on the
actual sensitivity, and has nothing really to do
with how your processing. Films of 800 or greater
sensitivity are affected by these low cosmic
radiation levels, and will fog. If you can get 4
inches of lead around your film, you could
probably stave off this fogging sufficiently.
That's a lot of effort to go to. The 'film
shield' bags don't do it.
Colour film is more sensitive, as the actual
sensitivity of the layers is greater than
equivalent B&W film, since the light levels are
reduced by the filter layers in the films. A
ISO800 colour film might have it's lowest layer
be equivalent to a true 2000 or greater
sensitivity. The fogging is related to the
sensitivity of the grains, and is unaffected by
the filters as the background radiation goes
unimpeded through those.
>
>
>Regards,
>Sonny
>http://www.sonc.com
>Natchitoches, Louisiana
>Oldest continuous settlement in La Louisiane
>?galit?, libert?, crawfish
>
>
>
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--
* Henning J. Wulff
/|\ Wulff Photography & Design
/###\ mailto:henningw@archiphoto.com
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