What was a use of photography during the 1920s?

Answer 1

The first permanent photograph was made in 1826 by Joseph Nicéphore Niépce using a sliding wooden box camera made by Charles and Vincent Chevalier in Paris. Niépce built on a discovery by Johann Heinrich Schultz (1724): a silver and chalk mixture darkens under exposure to light. However, while this was the birth of Photography, the camera itself can be traced back much further. Before the invention of photography,there was no way to preserve the images produced by these cameras apart from manually tracing them.
The development of the collodion wet plate process by Frederick Scott Archer in 1850 cut exposure times dramatically, but required photographers to prepare and develop their glass plates on the spot, usually in a mobile darkroom. Despite their complexity, the wet-plate ambrotype and tintype processes were in widespread use in the latter half of the 19th century. Wet plate cameras were little different from previous designs, though there were some models, such as the sophisticated Dubroni of 1864, where the sensitizing and developing of the plates could be carried out inside the camera itself rather than in a separate darkroom. Other cameras were fitted with multiple lenses for making cartes de visite. It was during the wet plate era that the use of bellows for focusing became widespread.

The first colour photograph was made by Scottish physicist James Clerk Maxwell, with the help of English inventor and photographer Thomas Sutton, in 1861[10]