Ansel Adams was an astounding photographer who influenced many aspiring landscape photographers and became a household name amongst photographers. However he seldom stepped out of his bubble of landscape expertise to photograph people. His friend, Imogen Cunningham had a much broader range with a focus on portraiture but never acquired the same recognition that Adams did. Annie Leibovitz also springs to mind as a master portrait photographer, but is far too modern for what I want to know; how did portraiture get where it is today?
My question is who shaped the portraiture scene pre 1960s?
In the name of keeping the question more specific, there are two specific people I wish to know about. Who first popularised the photography portrait (I suspect this will be pre 1900!) and who first popularised candid photography. Furthermore if there was someone that popularised the concept of superior image quality pre the f/64 club that would be very interesting to me.
I am aware that this is an atypical question that can be perceived fairly soft and broad question, so please keep opinion out of it and just state those that greatly influenced the sub culture whislt keeping it within the confines of the question. Any supporting references would be ideal.