Much has been written about the self-portrait in photography, almost everything is written and they say that if you leave someone a camera sooner or later they will take a photo of themselves. As in other artistic media, papers and letters, canvases and paintings have served to capture the author himself, photography could not be less in this task. Today with social networks and the use of mobile phones are the order of the day as something common and somewhat narcissistic, sometimes even neglected or distorted in its artistic form, which as a whole is what gives it beauty due to its diversity.
Self-portrait as art, in general, seeks to delve into the inner part of the person, to express outright a personal aspect as it is. Although we must not forget other more pragmatic reasons, of course the artist himself is always the cheapest model. Sometimes the self-portrait is valid to show unrealities, fantasies, reflections of the personality or of how we are human beings. In the end we can intuit that we observe how the photographer wants the world to see him.
As relevant people in this technical section of photography we could highlight Cindy Sherman, Lee Friedlander, Francesca Woodman or Kimiko Yoshida for example.
You can consult pages of photographers with great portraits and self-portraits in this post: Portrait and self-portrait photographers.