OBJECT:PHOTO shifts the dialogue about modernist photography from an emphasis on the subject and the image to the actual photographic object, created by a certain artist at a particular time and present today in its unique physicality. This shift is especially significant for a study of the period during which photography developed a distinctive formal language. A growing awareness of the rarity of images made between the two world wars has altered historians' considerations, encouraging new approaches privileging the originality of each work and the density of references each contains. This richly illustrated publication culminates a four-year collaborative research endeavor between The Museum of Modern Art's Departments of Photography and Conservation, and nearly 30 visiting scholars, on the material and aesthetic evolution of avant-garde photography in the early twentieth century. The 341 modernist photographs known as The Thomas Walther Collection, a major museum acquisition made in 2001, is presented in its entirety, establishing a new standard of depth for the medium. Essays by curators, researchers, and conservators consider the history of collecting from this era to the present and how deepening knowledge has shifted the perspective on the medium; the material facts of the Walther pictures as a baseline for understanding the development of photographic materials in this era; and how the intellectual formation of the writers of critical photographic publications of the era and the societal and cultural pressures of that historical moment inflected the photography's sense of its own history. Together with thematic, object-based case studies of groups of pictures that demonstrate new approaches in specific, divergent examples, these contributions reanimate the dialogue on this formative era in photography.