"Equivalent" is a series of gelatin silver prints created by Alfred Stieglitz between 1925 and 1931 that captures close up studies of clouds photographed against the sky. Stieglitz conceived these works as abstract compositions entirely divorced from narrative or representation, arguing that clouds could convey pure emotion and aesthetic experience through form, tone, and light alone. The series stands as a pivotal moment in photographic modernism, asserting photography's capacity for artistic expression equivalent to painting or music.