This response is solid radiation physics information. As everyone
knows, there are more 'experts' re film exposure in Airport security
than there are.......... Many have published a treatise on the
subject when it is simple physics. There is radiation exposure from
security x-radiation scanners. However, most forget what happens re
radiation exposure to themselves and their film when the plane climbs
to 33K ft or higher. Radiation exposure is additive, whether man or
film.
Most modern radiation scanners have auto-feedback circuitry to effect
an instant increase in tube output which maintains a constant
average/minimum penetration level (just like state of the art OM
metering). My approach: 1. First ask if possible to inspect rather
than scan; if not, 2. Request security to feed film through
separately, isolated from all other baggage (surrounding density) which
might necessitate an increase in dosimetry - - AND, lay the film such
that the beam passes perpendicular (NOT parallel) to the long axis of
the film cartridge. (I pre-pack in this geometry using a thin flat
plastic food storage container with a pop off lid.) X-ray absorption
is logarithmic. Cut the thickness ~ in half (width rather than height
orientation) and you decrease exposure by a log function.
Auto-exposure controls on the device will benefit you. Have never seen
a scientific demonstration of such specifically with a 35mm film
canister, but the radiation physics is solid science.
On Sunday, August 3, 2003, at 09:33 PM, Kennedy McEwen wrote:
Also, those X-ray bags - stick them in the lead recycler where they
belong! They cause *more* X-ray damage than they prevent these days.
When the machine operator sees the white blob on the screen all they
do is increase the exposure from the normally safe level for medium
speed film to something that will fry an image onto your shirt until
they can see what is inside. Only if they cannot see inside will they
request an inspection.
The problem is that you have two layers of lead sheet and the film
sits in the middle - so they have to double the exposure at the film
in order to be able to see what is inside the lead bag! In short -
you are better off without them and the only reason you don't get
fogged film when using them is because the level of exposure in modern
airport hand luggage machines is so low. Not so in the checked
baggage machines - NEVER put film in checked baggage - they *WILL* fog
the film.
Most places, even Heathrow where I have heard others complain that
they always insist on x-rays, will accept a visual examination of high
speed film or even low speed film if you can prove that you have to
pass through many machines on your trip (a multistage ticket is
usually enough). I have never had a problem at Heathrow or Gatwick,
just talk nicely to the operator and cringe when they tell you it is
safe. :-) On the other hand, I have put film through x-ray machines
without problems when there has been a serious language difficulty.
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