Over the decades, this body of work became an obsessive examination of her non-public self. Her name, her work, her hidden identity, were only discovered after her death, when an estate liquidator found the pictures packed into boxes and thought they might have some value. But who was this glamorous person in the Polaroids? The answer lay scrawled in red ink on the border of some pictures: April Dawn Alison. It was the first time the Schaefer family had heard the name.

The art of the reveal

The Polaroids – which are now being made public for the first time in a new book, April Dawn Alison, and exhibition at the San Francisco Museum of Modern Art – eventually found their way into the hands of Erin O’Toole, the book’s editor and show’s curator. What struck O’Toole when she first saw the pictures, she tells BBC Culture, was the quantity and the quality. The curator is well versed in vernacular photography, or snapshots that appear amateurish. These were not that, she says. “They were done by a professional photographer; they were well lit, beautifully composed, with this attention to colour. They were Polaroids but they were done by an artist.”