giverson@xxxxxxxxxxxxx writes:
<< fine wire grid is sandwitched with the film in the film
holder. When the x-rays strike the wire, they cause it to give off
(photons?) thus exposing the film.
I don't know if that also applies to 35mm film, but it would make sense
that the x-rays striking the zipper could do the same thing. Anyone on the
list a Physicist who can help us out? >>
The Flouroscopic material used for medical X-rays film packs (and for that
matter in flouroscopy video cameras) dramatically increases sensitivity of
film to X-rays but the film itself is inherently sensitive to X-rays it is
just the quantum efficiency is better to visible light. So using flouroscopic
material converts the energy to a band where the film is more sensitive. The
sensitivity improvement is by a very large factor 100's+. If you go to a
small hospital you are often more likely to have much higher X-ray dose for
exactly the same image because they may not use the latest (more expensive
high efficiency) screens. There is an excellent consumer guide to X-rays put
out by one of Naders medical consumer groups which details what are
acceptable limits for procedures and suggests you ask the hospital what their
levels are. If they don't know go somewhere else!
The zipper is unlikely to be flouroscopic and would be screened by
the camera body anyway but if metal it is probably just a density isssue.
Regards,
Tim Hughes
>>Hi100@xxxxxxx<<
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