What are the two major trends of documentary photography in the early 20th century?

At that time, there were two coexisting development trends in society, namely "McDonald's" and personalization. The former will make people become mechanical, simple and convergent, and lose the fun brought by colorful life, while the latter will make people become isolated, different and lose sympathy and cooperation. These two social trends will seriously weaken the social and psychological foundation on which theme photography depends: tenderness is replaced by violence, exquisiteness by simplicity, exquisiteness by nudity, and group value by individual value. Theme photography has encountered unprecedented value challenges. Therefore, a major theme and problem of contemporary western thematic photography is "seeking novelty" and "seeking change". Readers demand novelty, and photographers' reporting ideas and value choices will inevitably change. Traditional reporting techniques, themes and ideas are no longer suitable for the reading and psychological needs of contemporary audiences, and naturally they are not suitable for the needs of the market.