The late 19th century saw a rise in spiritualism in the United States and the world. Indeed, even Mrs. Abraham Lincoln was convinced that ghosts and spirits existed and this, in part, fueled others in similar beliefs. Photography at the time was still rather unaccessible and misunderstood by the ordinary citizen, their images usually taken by photographers in studios. Enter the dishonest photographer to the popular spiritual seance scene, and an opportunity for a past buck appeared. These unscrupulous photographers would bring a person into their “spiritual studio” and a “mock” seance was performed. Of course, when the photo was taken, the victim paid the money and instructed to come back the next day to see “what may have materialized.” What seems almost comical today was believed by many as revealing of long lost ancestors, or other ghosts that happened to be around them. With a simple dodge and burn technique coupled with the merging of another portrait or two to the sitters original—and voila! an industry was born. Today, these fake spirit photos are quite rare, and, if you can find one, often sell for hundreds of dollars.
Source: Accidental Mysteries