Cloud 9 is a group of nine original vintage photographs of the sky by esteemed photographers Imogen Cunningham, Alfred Stieglitz, and Edward Weston. Alfred Stieglitz photographed clouds from 1924 to 1935. He termed these cloud photographs Equivalents. For Stieglitz, the abstract forms and formations of clouds perfectly equated to the modern idea of equivalence, holding that abstract forms, lines, and colors could represent and evoke universal inner human states, emotions and ideas—a powerful notion which numerous later photographers recognized and emulated. Edward Weston's search for purity of form—the essential—seems simultaneously fulfilled and alleviated in his cloud studies. The abstract and impossibly fleeting nature of clouds played to his interest in form and texture, but even to Weston, clouds ultimately remain an elusive subject—free-association, subjective emotional reaction abound. Cunnigham’s clouds, while the most ‘cloud-like’ of the three, perfectly reflect her early interest in the abstract images created by the interplay of positive/negative space. This marked attention to positive/negative space in nature is seen also in her well-known masterpieces: Triangles, 1928 and Magnolia Blossom, 1925.