I've been traveling with my 4x5 camera for about a year now. And I've read this thread many times over. I've traveled across south-east asia and a few places beyond that. I haven't had any problems yet, but it doesn't hurt to be prepared. a brief summary of my conclusions
1. X-ray scans are cullmulative. The more scans, the more damage it will do.
2. Most people say; ISO 400 or under can withstand up to 5 scans before any noticable drop in quality (says kodak)
3. If you fly in the US, and have to adher to the TSA rules, you can request a hand inspection and they cannot say "no". If they do, you need to speak to someone higher up who knows the rules a bit better.
4. In you are flying through London, everything will be scanned.
5. MOST IMPORTANT: be polite about it. No need to sound like a drunken loon spouting rights and invasion of privacy. That will cause more harm than good.
Personally: I get my film hand-checked when ever I can. I arrive at the airport early so there will be no problems. I haven't had any problems in (Canada, Hong Kong, Taiwan, Australia).
Some airport security has said that 400 speed film is safe for x-ray use. I've gave the following explainations, and before I could finish... ...
1) "Actually, the x-ray process is cullulmulative. The more x-rays it goes through the more likelyhood that it will damage the film. I will be traveling through multiple airports and I'm trying to minimize the exposure to the film. THe reason is because X-rays are actually light. Albiet a small amount of light. When enough light hits the film, it will ruin the film. It is like jabbing a thumb into someones throat. For the first inch there will be no noticable damage, the skin is quite plyable. But eventually when the thumb punctures through the neck, there's going to be blood everywhere. I'm just trying to minimize that margin of error officier."
2) "Actually, I plan on devloping this film myself using something called 'pushing'. Put it simply, I can develop this film as if it were rated for ASA 6400. I also have a few sheets of film that I have experiemented on. The ASA equivalent would be closer to 25000. This is accomplished by enlongating the devlopment times and it can achieve a variety of different effects that I may utilize in the future, officer"