“It is not enough to photograph the obviously picturesque,” the photojournalist Dorothea Lange once said. Lange’s own images, far from picturesque, communicated the plight of America’s underdogs. Her 1936 photo of Florence Owens Thompson, which cast the Great Depression-era mother as a Madonna figure, rocketed Lange to worldwide renown. She went on to produce work clear in its mission to stir emotion and action in the viewer. It has been 80 years since Lange’s photographs of Thompson were exhibited at New York’s Museum of Modern Art, and now this show at MoMA places works from its own collection alongside Lange’s less frequently seen images. —J.V.