Xanthippe,
You are correct in that these are assumptions. Thats why I used the word assume. I never claimed otherwise.
You asked how could they prove it was real? I was just giving you what I would take as credible under the assumption "ghost" were real.
Remember the burden of proof is always on the one making the claim. (In this case someone claiming a picture of a ghost)
Displacement has nothing to do with this situation. Why should it leave residue?
If you can see it with your eye and take a picture its going to displace something to make itself visible.
But once again you could argue no it doesn't because its a ghost. To me this is like saying God can do anything. Then when asking him to appear thats the one thing he can't do or doesn't want to do.
So it would be pure speculation and assumptions on anyones part because noones proven ghost exist.
I've been in many so-called "haunted houses" that friends dared me to go into and never once saw or felt anything unusual. So I can only go on my personal experience. Thus that is why I don't believe in them to this day. Not one bit of evidence that they are anything other than peoples imagination running rampant.
Anyways I'm headed to bed but if you ever see a ghost or goblin,angel or demon, little green men from mars etc send them my way.