Which documentary photographer took photo's during the great depresion

Why did emerson most likely include the quotation from john brown speech

To create an illustration of perspective, this artist did all of the following except 1) show clear orthogonal lines 2) have an implied vanishing point 3) distort proportion to keep the background and foreground the same size 4) include value changes between the foreground and background i was thinking maybe 1

In 1910, who coined the term post-impressionism