Though spirit-photo hoaxes have been exposed, some photo-related coincidences and other phenomena are so spooky they could make one wonder whether something supernormal is really at work.
Hoaxes and debunkers are ubiquitous today, thanks to the Internet and technologies that allow for photo and video manipulation. But debunkers had their place more than a century ago as well, at the height of interest in séances and spirit photos.
Walter E. Woodbury was one such debunker. He uncovered what was behind a semi-frequent occurrence that produced—sometimes intentional, sometimes unintentional—hoaxes. Imagine the surprise of a photographer who would develop his shots and find something like this:

A "spirit photograph," from "Photographic Amusements," 1896, by Walter E. Woodbury. Public domain