Confused already

I have had the thought for some time that photography can be constructed in much the same way as painting; it can be a purely visual representation of a something, a person, a place. Both mediums can offer the same level of representation. The painter decides what to include and photographer has to decide what to leave out - an oversimplification but that's what I had generally thought. Additionally either medium can create a deeper level of image, through the use of metaphor, allegory, illusion, allusion or some other visual device, an artist can convey a thought, a message, a philosophy, a politic. Both mediums have been used to convey all sorts of messages since their inception, clearly painting for much longer, the period leading up to the enlightenment was much more straightforward (inasmuch as I know about the medium) than after, but nevertheless, if we consider the 20th century where the level of sophistication of the artists operating in either field was roughly equal, certainly by the second half of the century, then the visual language used was a common currency. At least that was what I thought.
I started to read Clarke's "The Photograph" earlier today and I got very confused about some of what he was saying. In the first essay p23 he states.."We can never enter a photograph's 'depth'. Roland Barthes rightly complained about the frustration involved in the misplaced assumption that the closer we look at a photograph, the more we see." I take this to mean that Clark is agreeing with Barthes that, as he states earlier in the paragraph, it is "flat" it is dimensionless, that we can only .."look over it and across it. We can never enter a photograph's depth". And yet over the page p24 Clark starts to deconstruct Olivia Parker's photograph "Bosc"and spends a paragraph and a half reading the image. Indeed the second paragraph starts with "But this is also an image about photographic meaning, an essay on the capacity of the photograph to both reveal and conceal its meanings..." Unless Clark is able to see all of this in an instant, to collate these hidden meanings and receive its conveyed messages in the moment that he "look(s) over it and across it" then either there is a large contradiction or, more likely I am unable to see the logic in his essay. I shall read on and hopefully all will be revealed - or maybe I will forget about this (I doubt it somehow).

In chapter 2 Clark discuss's Diane Arbus' "Identical Twins. Clark conjects that there is a tension derived from the inception of photography, the daguerrotype, that "underscore the idea of a photograph as a literal record. Each twin is a reflection of the other. But "identical" infers 'identity', and the portrayal of a self limited to the surface presence of a single entity." Clark then goes on to talk about how the viewer can then only look at the differences in the subjects apparent in the photograph, like a "spot the difference" party game. I would add that he also goes to talk about how "..establish(s), both literally and symbolically, the basis of reading the image". But I said I would leave that until it resolves itself.
The issue surely for the Arbus photograph is as Clark (I think quite rightly) states in his first essay p24 p25. that "Finally, and perhaps most significantly, a photograph fixes a moment in time." I think I had come to this conclusion in my "Truth" blog entry July previously. Clark goes on to quote Damisch saying the photograph '...it does so only in so far as it isolates, preserves and presents a moment taken from a continuum".
Well, if Arbus had called the picture sisters, or two girls in similar dress, then no tension, as Clark describes, would arise. We, according to Clark have taken direction from Arbus, in this case they are identical sisters, but we have ignored his own declaration that a photograph is a "moment in time". A different title, in Clark's conjecture, would no longer deliver a seminal work of art, but another shot that stays in the drawer as the tension derived from the title would not have us look to "ring" all the differences between the sisters.
But I don't think so; in my semi literate vocabulary I would state that we would know that in that moment of time all things can shape a face, eyes shutting or opening would effect the appearance demonstrably, one or other having a cold, or an itchy nose at the point of shutter release. The camera lies incessantly, it is Walter Mitty, it doesn't know its doing it, it can't control itself - it doesn't control itself. The artist presses the shutter.
The photograph can be read, as I think Clark means to say; but as with any work of fiction, any picture however fabricated there maybe many interpretations, but only one truth and that is the one Arbus wanted to deliver, what Parker wanted to convey.
I also know that I need to develop my vocabulary and hopefully I'll catch Clark up before he confuses me completely again.