|Source: The spirit photographs of William Hope|
Hope started out as a carpenter, but in 1905 he stumbled across his spirit photography technique. He formed a group of photographers called the Crewe circle and went into the Spiritualist business.
The end of WWI greatly boosted his business as people sought images of their lost loved ones. His business was quite successful, among his clients was Sir Arthur Conan Doyle.
He was investigated several times, and it was revealed that all he was doing was making double exposures, with the images of old photographs of loved ones already faintly exposed on the plates he brought to the sessions. Still, he had his supporters up until his death.
His pictures look ridiculous to our modern eyes, but I suppose that back in the day, when the photographic process was a mystery to most people, they were convincing enough.