section: Theories of mechanical aid
question: What is the Hockney-Falco postulation?
article: Johannes Vermeer
candidates: Vermeer's painting techniques have long been a source of debate, given their almost photorealistic attention to detail, despite Vermeer having had no formal training, and despite only limited evidence that Vermeer had created any preparatory sketches or traces for his paintings. In 2001, British artist David Hockney published the book "Secret Knowledge: Rediscovering the Lost Techniques of the Old Masters", in which he argued that Vermeer - among other Renaissance artists including Hans Holbein and Diego Velázquez - used optics, and specifically some combination of curved mirrors, camera obscura and camera lucida, to achieve precise positioning in their compositions. This became known as the Hockney–Falco thesis, named after Hockney and Charles M. Falco, another proponent of the theory. Working independently, in 2001 British architecture professor Philip Steadman published the book "Vermeer's Camera: Uncovering the Truth behind the Masterpieces", which specifically claimed that Vermeer had used a camera obscura to create his paintings. Noting that many of Vermeer's paintings had been painted in the same room, Steadman found six of his paintings that are precisely the right size if they had been painted from inside a camera obscura in the room's back wall. Supporters of these theories have pointed to evidence in some of Vermeer's paintings, such as the often-discussed sparkling pearly highlights in Vermeer's paintings, which they argue are the result of the primitive lens of a camera obscura producing halation. It was also postulated that a camera obscura was the mechanical cause of the "exaggerated" perspective seen in "Lady at the Virginals with a Gentleman" (London, Royal Collection). In 2008, American entrepreneur and inventor Tim Jenison developed the theory that Vermeer had used a camera obscura along with a "comparator mirror", which is similar in concept to a camera lucida but much simpler, and allows for easily matching color values. He later modified the theory to simply involve a concave mirror and a comparator mirror. He spent the next five years testing his theory by attempting to re-create "The Music Lesson" himself using these tools, a process captured in the 2013 documentary film "Tim's Vermeer". This theory remains disputed. Aside from the accurately observed mirror reflection above the lady at the virginals, there is no historical evidence regarding Vermeer's interest in optics. The detailed inventory of the artist's belongings drawn up after his death does not include a camera obscura or any similar device.