Hockney–Falco thesis

The Hockney–Falco thesis is a controversial theory of art history that argues that advances in naturalism and accuracy in Western art since the early Renaissance were due primarily to optical aids such as the camera obscura, camera lucida, and curved mirrors, and that the use of these aids was more widespread than previously believed. The theory was proposed by artist David Hockney in 1999 and further advanced with physicist Charles M. Falco since 2000 (together as well as individually).

In his 2001 book, Secret Knowledge: Rediscovering the Lost Techniques of the Old Masters, Hockney more extensively analyzed the work of the Old Masters and argued that the level of accuracy represented in their work is impossible to create by "eyeballing it". It formed the basis for the 2002 BBC documentary David Hockney: Secret Knowledge, with some new ideas and experiments that in turn inspired additions to the second edition of the book (2006).

Nineteenth-century artists' use of photography had been well documented, and many art historians had already suggested that certain artists had used the camera obscura for their work (most notably 18th century painter Canaletto and 17th century painter Johannes Vermeer), but Hockney believed that nobody had previously suggested that optics had been used as early and widely as he suggested. Many art historians contested the hypothesis, while others found the debate "hyped" and pointed towards earlier studies and writings.