After 1945, American photography changed. The formal studio portrait, known as a “sitting,” became old hat. Informal images, snapped fast—a “shoot”—took over. This shift opened up the boundaries of what was accepted as interesting. The energy of big cities, the commonality of small towns, experimental tableaux, movement and blur—postwar American photography was both innovative and down to earth. This show explores it all, with works by Ansel Adams, Diane Arbus, Walker Evans, Lee Friedlander, Nan Goldin, Cindy Sherman, and more. —L.J.