Meaning in a Photograph

This will be a simple and short post on the meaning of an image in a photograph. We should always remember that there are three factors that contribute to meaning and interpretation of a photograph:
The first obviously would be the Subject Matter or what is depicted.
The second is the Photographer; who is she/he, what is she/he like, what is the photographer's intention or purpose of shooting the image?
And the third is the Viewer; who is the viewer, is the viewer the targeted audience, what is the viewer's cultural or educational background, does the viewer have a background knowledge about the subject matter or the photographer?

Think of a candid photo of a person... suddenly it's not just a normal 'snapshot' anymore when the sitter is actually a famous person, or when you realize that the photographer is actually Andy Warhol for instance (that is if you know who Andy Warhol is...).