Ghost photos

      A while back I shot a picture up our front stairs which seemed to show what I thought appeared to be a phantom of a womans head, at about the right height for someone coming down the stairs. It wasn't really that plain. My wife thought it was probably a film or development flaw. I had two guests who thought they could see what I saw, but another said it looked more like a phantom portrait.  A paranormal investigator asked to see it. I sent it to him and though he noticed a discoloration he failed to see a face; but thought it promising enough that I should reshoot the picture and take the staircase from several other angles and make the shots just before or just after the full moon. I did the experiment and the shots all came out clear with nothing unusual in sight. I have tried it again, at full moon. But those shots have not been developed as yet.