Stieglitz's famous photographic cycle of O'Keeffe began in 1917 when she was 30 years old and he was 53 and ended in 1937 when ill-health caused Stieglitz to put down his heavy camera. In over 300 black-and-white photographs—some of them candid shots, many more of them showing her nude and provocatively posed—Stieglitz revealed to the world O'Keeffe's strengths and vulnerabilities, and almost single-handedly defined her public persona for generations to come. (https://www.metmuseum.org/toah/works-of-art/1997.61.12/)