Susan Sontag had a great deal to say about the in what ways and to what degree we conflate photographs with reality. Things are different now, 40 years down time, but some things remain the same. We still get irrationally worried and upset when people photograph our children, which suggests that certain ancient superstitions remain.
If you haven't read Sontag, I submit that you're missing some of the basic work that's been done on these admittedly pretty esoteric and ultimately not terribly interesting issues. If you have, then you know what I'm talking about. She had some pretty good thoughts and wrote some of 'em down.
But Sontag didn't write so much about the reality of photographs as she did about the reality of photography. There is a difference. She did touch on the idea that people do relate to a photograph as reality, but her real point was the effects of photography on culture. Her essays were on the anthropology of photography, and the effects are essentially the same whether people think a photograph is real or whether they see it as this illlusion/representation that has been under discussion here.
Because I do a lot of "people pictures" I've always been interested in the philosophy that Sontage expressed. She discussed the fact that many people see images, whether drawings or photographs, as usurping a spiritual part of the subject depicted. Sontag famously pointed out that it is an assault to photograph a person:
"To photograph people is to violate them, by seeing them as they never see themselves, by having knowledge of them that they can never have; it turns people into objects that can be symbolically possessed. Just as a camera is a sublimation of the gun, to photograph someone is a subliminal murder - a soft murder, appropriate to a sad, frightened time."
Which discusses the effects of photography, not the photograph. But necessarily that discussion at time centers on exactly what a photograph is in the same sense we have been discussing:
"such images are indeed able to usurp reality because first of all a photograph is not only an image, an interpretation of the real; it is also a trace, something directly stenciled off the real"
There are interesting criticisms of Sontag, some of which relate to the style of argument used here by some. One is that her early essays were written before she had the credentials that she ultimately did! It can also be argued that she was even to begin with a credible authority, but some like the idea that until she was partnered with Annie Leibovitz, Sontag didn't know photography well enough to analyze it accuratly. Seems to be nothing more than a well orchestrated and worthless distraction.