Dr Flash wrote:
> Sorry, I don't buy it. Why would x-rays preferentially affect only
> the outer edge of the sprocket hole area? It would zap the entire
> surface of the film. Also, why would only half the roll be
> affected?
It actually does zap the entire surface of the film and if you
compare the base density of the first part of the roll with the
second part you can usually see noticable fogging. From the rolls
I've seen like this, the radiation only seems to penetrate maybe four
or five layers. It easily goes through the thin metal cartridge.
> unable to penetrate the entire thickness of the cartridge, the
> exposure pattern would be oscillating since one half of every turn
> around the film cannister's reel would be on the back side of the
> reel from the perspective of the x-ray source.
In the cae of airport x-ray damage, this is most typical. In fact,
you'll usually see pretty unusual patterns as the radiation usually
is coming in at an angle from off the end of the cartridge. The
radiation that is used to destroy biologicals is different. As this
is almost always a "dual-pass" and the chamber is somewhat reflective
you'll get the roll damaged from all sides.
I asked the question about the outer edge of the film beyond the
sprocket holes because of leakage around the crimped ends of the
canister, which is another common source of light leakage.
AG
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