to tkamiya:
Actually, the agents in the US do not have an "mA" knob to increase exposure. In the USA, the formal regulation is quite clear that you have the right to hand inspection of photographic film. Some airports are good about posting this regulation, but you will find agents who are unwilling. A polite request by me has always worked in the US, but not abroad. The regulations even recommend hand inspection for large format and professional film. The magic words "professional reversal film" usually work for me. When returning with exposed sheet film in original boxes, I don't push my luck in case an ignorant inspector wants to open the box. One x-ray (carry-on) won't affect sensible speed sheet film. Incidentally, if the agent swabs the outside of the film box for explosive residue inspection, that has no effect whatsoever on the film.