Jacob August Riis was a Danish American social reformer

Reform movement

A reform movement is a kind of social movement that aims to make gradual change, or change in certain aspects of society, rather than rapid or fundamental changes...

, "muckraking

Muckraker

The term muckraker is closely associated with reform-oriented journalists who wrote largely for popular magazines, continued a tradition of investigative journalism reporting, and emerged in the United States after 1900 and continued to be influential until World War I, when through a combination...

" journalist

Journalist

A journalist collects and distributes news and other information. A journalist's work is referred to as journalism.A reporter is a type of journalist who researchs, writes, and reports on information to be presented in mass media, including print media , electronic media , and digital media A...

 and social documentary photographer

Social documentary photography

Social documentary photography may be defined as the act of recording, with a camera, human beings in their natural condition. Often is also refers to a socially critical genre of photography dedicated to showing the life of underprivileged or disadvantaged people.-Origin of social documentary...

. He is known for using his photographic and journalistic talents to help the impoverished in New York City

New York City

New York is the most populous city in the United States and the center of the New York Metropolitan Area, one of the most populous metropolitan areas in the world. New York exerts a significant impact upon global commerce, finance, media, art, fashion, research, technology, education, and...

; those impoverished New Yorkers were the subject of most of his prolific writings and photography. He endorsed the implementation of "model tenements" in New York with the help of humanitarian Lawrence Veiller. Additionally, as one of the most famous proponents of the newly practicable casual photography, he is considered one of the fathers of photography due to his discovery the use of flash

Flash (photography)

A flash is a device used in photography producing a flash of artificial light at a color temperature of about 5500 K to help illuminate a scene. A major purpose of a flash is to illuminate a dark scene. Other uses are capturing quickly moving objects or changing the quality of light...

 in photography

Photography

Photography is the art, science and practice of creating durable images by recording light or other electromagnetic radiation, either electronically by means of an image sensor or chemically by means of a light-sensitive material such as photographic film...

.