(The Platonic original of a photograph)
That is, you're talking about the "truth" of photography in terms of a kind of optical magic, in which the information in a bunch of loose photons is captured wholesale as a physical, concrete image. We all know that doesn't happen---the photo loses polarization, timing information, and the wave properties of light, for a start, and that's without considering optical imperfections of the lens or spectral and sensitivity limitations of the capture medium---but you write as if it's very viscerally clear to you that *those* departures from perfect accuracy are not important, while *other* departures are enormously important.
Which, y'know, take your gut feeling and run with it! I'm not going to argue that you shouldn't have that attitude to the medium. But I don't see that it has any special claim to being The Way Photography Really Is, or that any particular choice of the cutoff point between "not important" and "enormously important" is intrinsically more right than any other.
Agreed, absolutely. I kind of think that these different interpretations are all we've got, though, unless you abstract your concept of "the medium" away from photography and into general visual art. While we can try to understand one another's interpretations and get out of our own confined assumptions, I think the idea of a transcendent Grand Unified Theory of Photography is a fiction, and epistemological arguments about it are founded on sand.It seems to me that most of the contributors here want to define it simply by how they use it. That, I think, is why there are so many different definitions, and angst over a sense that no one else understands what it really is except for "me". When one constructs a definition solely around one's own unique interaction with the medium it's not surprising that one ends up with an almost infinite number of interpretations.
 What distinguishes photography from painting, I submit, is *solely* the process; it's possible for a technically skilled painter to make a viewer say "wait, is that a photo?", or an inventive photo printer to make a viewer say "wait, is that a painting?", which by itself almost proves that you can't really distinguish the two media purely on viewable characteristics of the image. The two certainly speak the same language between the creator and the viewer, and what can be said about one in terms of image and communication can be equally said about the other. Discuss?