How can you get x-ray vision?

I hear if you put your video camera on "night vision" and put unused negative camera film over the lens, then you can see through certain substances. Through most outer were, but if you looking to see through under were it wont work because it wont go through cotton, but you can go to a swimming pool and see thru cloths there, but i don't think that is legal, you now if the cops catch you.