Since beginning his career in the 1960s, British artist David Hockney has experimented with mediums ranging from oil painting to photo collage. Each requires a different technique, and Hockney's techniques changed accordingly depending upon the project.

David Hockney was born in 1937 in Bradford, England. After studying at the painting school of London's Royal College, Hockney sold some of his paintings to finance a trip to New York, where he became immersed in the city's art scene. By the late 1960s, he was seen as one of the leading figures in modern art, and his work was internationally acclaimed for its stark naturalism. During the late 1960s and 1970s, Hockney became well known for his series of paintings of Los Angeles swimming pools, which are among his best-known work. In the 1980s, he began experimenting with photo collage, using snapshots he took with a Polaroid camera. Hockney's experimentation continued throughout the 1990s, using media ranging from computer printers to fax machines. Hockney made headlines in 2001 when he proposed a controversial theory about how the Old Masters attained such realism in their paintings.

Hockney's love of photography and interest in the Pop Art movement are evident in the entries of his pool series, the most famous of which, "A Bigger Splash," was completed in 1967. For these, Hockney focused on the interplay of colour and light. Hockney's portraiture has evolved since his early paintings, yet has been a consistent part of his work throughout his career. The artist also enjoyed working in a variety of media beyond painting, including etching and printmaking.

In the early 1980s, Hockney's interest shifted to photography and photo collages. He pioneered a new technique for creating photo collages that he called "joiners." This involved taking numerous photos of the same subject --- taken from different angles but in succession --- and joining them together in a collage. Hockney's intent was to give still photography a visible element that reflected the passage of time. In 1982, Hockney photographed the Grand Canyon, producing a photo collage he called "Grand Canyon With Ledge, Arizona 1982." This and other photo collages on the Grand Canyon formed the basis for a series of 1998 paintings of the Grand Canyon, "Composition Study for a Bigger Grand Canyon." For this study, Hockney combined cubist techniques --- geometric, overlapping shapes --- with the style used in his photo collages to produce a series of paintings.

Hockney made headlines in 2001 with his book and accompanying UK TV program, "Secret Knowledge," which detailed his theory that the Old Masters used a camera obscura technique that helped render their paintings so realistic. After studying thousands of prints, he came to believe that the proportion and detail were too precise to be done without assistance. He came to the conclusion that these painters had used a various tricks --- including special lenses, a darkened room and special mirrors --- to project the image of their subjects onto the canvas; the painter then just had to trace the image projected. Because the image is projected upside down, the painter would then set the painting upright to finish the details. His theory caused outrage among some in the art world, who felt he was diminishing the skill required to create these iconic paintings. Hockney actually used the camera obscura technique himself. In his book, Hockney displays paintings of security guards at the National Museum that he produced using optical aids as an example of the technique.