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Re: [OM] Help from UK members, were to get film

Subject: Re: [OM] Help from UK members, were to get film
From: whunter <whunterjr@xxxxxxxx>
Date: Sun, 3 Aug 2003 23:22:51 -0400
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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