and the dead. He focused on people whose faces showed such expressions as pain, kindness, and resignation. His work during this time produced a large collection of photographs, many of which are familiar to Mexicans as they have been widely reprinted and reused, often without credit to Casasola. After the war, Casasola continued to photograph common people, especially migrants to Mexico City during the 1920s and 1930s. His total known archives comprise about half a million images with many of his works archived in the former monastery of San Francisco in Pachuca. Kahlo and Casasola are considered the two most important photographers to develop the medium in Mexico, with Kahlo defining architectural photography and Casasolas establishing photojournalism. Neither man thought of himself as an artist—especially not Casasolas—who thought of himself as a historian in the Positivist tradition, but the photography of both show attention to detail, lighting, and placement of subjects for emotional or dramatic effect. For the rest of the 20th century, most photography was connected to documentation. However, artistic trends from both inside and outside the country had an effect. In the 1920s, the dominant photographic style was Pictorialism, in which images had a romantic or dream-like quality due to the use of filters and other techniques. American Edward Weston broke with this tradition, taking these effects away for more realistic and detailed images. This caused a split in the photography world between Pictorialists and Realists both inside and outside of Mexico. Weston and his Italian assistant Tina Modotti were in Mexico from 1923 to 1926, allying themselves with Mexican Realist photographers Manuel Álvarez Bravo as well as muralists such as Gabriel Fernández Ledesma. These photographers' political and social aspirations matched those of the muralist movement and the new post-Revolution government. Mariana Yampolsky, originally from the U.S., became an important photographer in Mexico. Photography and other arts shifted to depictions of the country's indigenous heritage and the glorification of the Mexican common people. This was mainly to reject the elitist and heavily European values of the Porfiriato, along with the increasing cultural influence of the United States in favor of an "authentic" and distinct Mexican identity. Another was the government's decision to use this imagery, rather than the still-fresh memories of the battles and atrocities of the Revolution to promote itself. Manuel Alvarez Bravo experimented with abstraction in his photography and formed his own personal style concerned with