I believe that the last ten years has disproved ghosts, spirits, bigfoot etc etc etc.
Everyone has cameras now, if they existed we would know by now for sure.
I know this post is old, but this is the thing I needed to answer with my experience.
Ok, so what is a real experience of a spirit or ghost like?
Welp, I have experienced them a few ways....
1) As a physically indistinguishable "looks like a video" non-interactive type being. (Exceedingly rare.)
2) As an interactive "mental image"... (this is the most common way for them to visually appear...) Generally, it will feel like you see them "in your head"... Almost like you are imagining them... without your control...
3) Non-verbal emotion streams
4) Pure thought streams... Telepathic, and no other appearance.
5) Physical sounds. (Or, at least they seem that way... Very rare as well.. )
Cameras only have a chance to detect the first case, and that's assuming that it's not just an extreme case of #2 (which it probably is)... The spiritual hardware the human has isn't replicated by any machine thus, in my experience, machines would be a terrible way to experience them. This is pretty comparable to the way we discovered atoms and how they work without ever seeing them other than to observe certain behaviors and infer the rest. In essence, we are each spirits we just happen to possess a body here -- thus we are not completely unlike them in many ways..
It makes sense if we could use these faculties we should be able to interact directly.
Some of the nicer spirits I know simply are considerate of the humans around them and stay in mode 3 or 4. What would a camera tell you of them?
Mostly, they don't want to frighten you.... If you aren't paying attention this could come across to you as rambling thoughts or feelings in your head... Most people would miss it... Just think they are daydreaming or whatever...
For every spirit that engages in 1 or 2 there are probably hundreds engaged in methods 3 and 4. It's easier for them to communicate with these two... and usually that's what happens...
Anyway, I figure I'd share feedback from a perspective of someone who is engaged with these things. I hope it helps others to understand.
I'm not sure a camera would ever pick up any of these things -- I think they are mostly something only we can pick up.