October has long been associated with ghosts – from ancient Celtic festivals to ward off restless spirits after harvest time to the modern standby of using an old sheet to make a last-minute Halloween costume. In the middle of the 19th century, however, popular portrayals of ghosts became a year-round staple, in part because photographers discovered that they could depict them.
The first ghost photographs were accidents. Early cameras required 30 seconds or more to take a photo. If someone wandered briefly into the shot, the resulting picture would contain their ghostly trace superimposed over substantial furniture, buildings or people who had held still for the full exposure.
