from what I know, there is usually 2 type of X-ray that airport uses.
One for hand carried luggage - the power of it is usually lower, film with ISO 400 or less should pass through with no notice effect.
Another for checked-in luggage - This one usually higher power, ISO 100 or below should pass through OK.
If u r going to US, there is a even more powerful X-Ray. No film should pass through that. But u must be lucky to get it cos they only does random check for that. Picked by the computer according to the airline staff. I kana on my US trip last yr with my brother's family. Anyway, US custom staff hand checked camera after X-ray too. Just in case that it is a bomb or something disguise as a camera.
If u do not want the film to go through any X-ray at all, u can always keep them in a separate bag and let the custom staff know. Most of them will hand check if u tell them u got film inside.