John Szarkowski is credited with establishing photography as an art form.
He helped validate photography, especially documentary photography in North America as an art and made others notice the work of such notable photographers as Diane Arbus, Jerry Winogrand, Lee Friedlander, Walker Evans and Edward Weston. If you haven’t heard of these photographers do some research and it’ll help you discover what a good photograph is all about.
Diane Arbus 1962
Get your hands on his 1973 book Looking at Photographs: 100 Pictures from the Museum of Modern Art.
“As an artist you look at other peoples work and find out how it can be useful to you” J. Szarkowski.