When you watch a movie, what's you can see it's the result of the filmation, which can be manipulated in ways difficult to see or detect. I'm not saying that no film in history has capture a ghost, but it's impossible to be sure that the ghost is "real" and not a trick.
I'm a pro photographer and I find some of the supposed "ghost photos" laughable - someone gets a blurred figure with a time exposure in a gloomy church and hey, it must be a ghost!
They are SO easy to fake with double exposures and even easier using photoshop and digital media that you can never really trust a photo of a ghost unless you were there and saw it (or didn't see it)
Paranormal sites also do themselves no favours with their "orbs" (flash-illuminated dust)
I do believe in them though, I just maintain a less gullible attitude than some people.
As I said above, anything can be faked, but apparently these weren't, you'll have to dig further on this site for all the scietific controls that they went through, but no one has successfully debunked this experiment. Check out "The Scole Experiment" on Amazon.