how is everything in focus?--do xray machines work by "casting an x-ray shadow" or something---I'm thinking that's what's going on....so the xrays have to come out perfectly parallel to each other then, right?
Unlike a camera with film which captures the reflected light through a lens which has projected it on to the film, the x-rays go through the subject and strike the film or sensitized plate. The difference in densities of what is being x-rayed stop or slow the x-rays so the amount of x-ray striking the film will determine shades on the film. Something that is radio-opaque will be clear or white and something that is radiolucent will be black and so forth. The setting on the x-ray machine can be adjusted to emit different degrees so the head shot by an orthodontist is set to show both hard and soft tissues.