All art is a vision penetrating the illusions of reality, and photography is one form of this vision and revelation.
Hear, hear, Alain. Exactly! Art hasn't much to do with the quality of printing, the sharpness of the lens, etc., etc. -- or the "artist's" intent or skill or imagination. It has to do with a transcendental experience you encounter through the object or performance that's is the "art." In my opinion, Archibald MacLeish never was a great poet, but he was a very good teacher and he understood what makes art, in this case a poem, effective. In his book, "Poetry and Experience," here's what he had to say about Dylan Thomas's "Do Not Go Gentle Into That Good Night." a poem powerful enough to have been read to the U.S. at large as a requiem the day after John Kennedy's murder.
"I think we can probably agree that this poem is a trap and cage in which a heaven and earth we recognize is somehow caught. A boy’s agony, face to face with the humility and submission of a dying father, is held here in such a way that we not only know the pain but know something we had not known before about that mysterious turning away which is the cause of pain. But can we go further still? Can we say how this knowing is given to us?
"We can take, I think, at least one step. We can agree that whatever it is we know in this poem, we know only in the poem. It is not a knowledge we can extract from the poem like a meat from a nut and carry off. It is something the poem means — something that is gone when the poem goes and recovered only by returning to the poem’s words. And not only by returning to the poem’s words but by returning to them within the poem. If we alter them, if we change their order, though leaving their sense much as it is, if we speak them so that their movement changes, their meaning changes also."
In your words, Alain, the poem penetrates "the illusions of reality" and brings us face to face with something we can't put into words. The same thing's true of a photograph you properly can tag with the label, "art." I'm not sure MacLeish's word "know" in "whatever it is we know in this poem" is the right word, but I can't think of a better one. If the experience you have when you look at a photograph isn't transcendental -- if it doesn't "penetrate the illusions of reality" -- if you actually can explain in words what's important about the image, then it isn't "art." It may be beautiful, it may satisfy the rule of thirds, it may have diagonals, repitition, etc., etc., and it may be significant in some temporal way, but unless the transcendental experience is there, it isn't art.