X-rays machine - no probs after putting film through 13 times!

Not a question, but I will nonetheless write my findings regarding

the matter of whether or not X-ray machines in airports can harm film

(in my case, all ASA 100).

 

I recently came back from Mexico, where the film was put through X-

ray machines 7 times in total. One of my films was an old one which

I'd taken to Peru last year (given I hadn't used it, I left it in the

fridge and took it to use in Mexico). During my trip to Peru, that

particular film had also been subjected to 6 X-ray screenings, ie, it

had been through an X-ray machine a whopping 13 times in aggregate.

 

No problems whatsoever were noted on the processed film, which in my

mind confirms the many threads of info which I have previously read

on the matter. Of course, my findings relate to a slow ASA 100

speed ... perhaps 400+ could produce different findings. At Heathrow

airport, the X-ray person was telling someone that their machine was

even safe for 3200 speed, although I'd have my doubts if you could

really expose that high speed film 13 times without damage.

Jon:

 

While your post confirms my own flying experience; I have seen film go through fifteen or twenty times without damage, I predict it will do nothing to stop the flood of people asking questions about airport x-rays.

 

I see two reasons for this:

 

1) Rumors die hard.

 

2) Labs and others who want to blame something besides themselves for film damage will jump to the airport x-ray thing.

If we assume that machines are calibrated to leave 800-speed film unharmed through 4 to 8 passes (reasonable numbers for a full trip) and that film sensitivity to X-ray is proportional to its sensitivity to light, ISO 100 film can be passed 30 to 60 times through those machines with no harm, and 1 or 2 passes would even be harmless on ISO 3200.

Jon, a couple of years ago, I started reading about the newer Xray machines that could damage film. One of the big points they made in those articles was that the newer machines were not installed at all airports- just in selected places (this in the US only, as I recall), and they weren't saying where. Additionally, the problem with them was they would zoom in on "opaque" objects and scan at higher power. The problem in this case is that no amount of running film through a machine in Mexico will tell you how safe it is with a different machine elsewhere. Even running it through the same machine twice wouldn't necessarily give you the same results each time. Sort of leaves it as a guessing game, still.

<p>Jon, thank you for reporting your results. What this test shows is that ASA 100 film produces acceptable results after 13 airport x-rays. It does not show that there was no loss in quality. The experiment lacked a control. It could be that there was some slight fogging that reduces the contrast in the shadows (assuming that it was negative film).</p>

 

<p>A better experiment that some frequent traveler might want to try would include a control. Take two identical films purchased at the same time and make two identical exposures at the same time with the same camera and lens. Leave one film at home and travel with the other. Try to keep both films at the same temperature, e.g., in the refrigerator when not traveling and both at room temperature when traveling. Then after many X-rays, develop both films and make prints from each. Do the film base densities differ? Has a raised fog level reduced contrast in the low densities of the film? Can you see any differences in the prints?</p>

 

<p>For what it is worth, the US Transortation Security Administration recommends <a href="http://www.tsa.gov/public/interapp/editorial/editorial_0085.xml">no more than 5 x-ray exposures</a>: "<i>Carry-on screening equipment might also damage film if the film passes through more than 5 times</i>". The TSA further states "<i>Protect your film by requesting a hand-inspection for your film if it has already passed through the carry-on baggage screening equipment (X-ray) more than 5 times</i>".

 

<p>The new machines mentioned by Stephen have two stages. If the second stage, similar to a CAT scanner, is used, film will be damaged. Film should not be placed into checked baggage because it might go through one of these machines. If they use this type of machine on your carryon luggage, you will recognize it from the larger size. All of these machines that I have seen carry prominent signs instructing that film should be removed. In the USA, these signs are required by law: "<i>If the X-ray system exposes any accessible property or checked baggage to more than one milliroentgen during the inspection, the sign must advise individuals to remove film of all kinds from their articles before inspection.</i>"</p>

 

<p>A previous thread with some discussion of the laws in the USA: <a href="http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=005dEg">Hand check of film at airports</a>. For the legal regulations in the US, go to <a href="http://www.access.gpo.gov/nara/cfr/cfrhtml_00/Title_49/49cfr1544_main_00.html">Title 49, Part 1544</a> and click on the link to 1544.211, "Use of X-ray Systems".</p>

This topic was recently discussed very thoroughly in the Nature Forum. To make a long story short, I have some ISO 400 film (Provia 400) that went through 15 scans in the US, Australia and Norway as <B>hand-carry</B> luggage between two trips in 2002 and 2003, and there is no trace of X-Ray damage at all. See <A HREF="http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=005tcT">this thread</A> for the details.

<P>

However, if you put any film inside your checked luggage, even one scan could damage your film completely as they use different types of X-Ray machines for checked luggages.