This both included Riis taking his own photos as well as him using the images of other photographers .
In January 1888 , Riis bought a detective camera and went on an expedition to gather images of what life was like in the slums of New York City .
This both included Riis taking Riis ' own photos as well as him using the images of other photographers .
In January 1888 , Riis bought a detective camera and went on an expedition to gather images of what life was like in the slums of New York City .