Explain contingency in relation to Barthes camera Lucida. Photography is contingent on the real. It is a physical consequence of the...

"A photograph is invisible; it is not it that we
see." 

Barthes was not trying to analyze photography for
its social or cultural impact.  Nor was he, as Benjamin might have been, investigating
the significance of the mass reproduction of art, images or even machines and technology
in general.  Barthes was looking at the ontological nature of photography or 'a
photograph,' what it is, in and of itself; it's being.  He begins with noting that a
photograph is inextricably linked to its referent.  In other words, a photograph of a
woman in a field is 'a photograph of a woman in a field.'  That sentence just sounds
redundant.  But, the point is that the photograph itself is what I would call a 'looking
moment' of that Real woman in the field. 

Think of it this
way: the photograph is a window pane.  You look out (through) the window and see the
woman in the field.  If you could freeze that 'looking moment' for the smallest
increment of time, you would have the concept of the photograph, frozen, as it were, on
the window pane. But the window pane is transparent; it is nothing. Yet, the image that
you would freeze on the pain/photographic plate is a sign or signifier that refers to
the real woman in the field. How can a physical referrring sign, essentially - like the
window - be made of nothing?  A signifying, transparent 'nothing' can only be something
in relation to what it refers to.  Therefore, the photograph,
analogous to the window pane, is contingent on the real
woman in the field. 

The photograph, itself
(physically) is capture light, framed by the camera obscura; captured as if you were to
capture your momentary 'looking' through the window pane. The captured light
(photograph) is not the woman; it is not Her and yet it comes from her.   It is the
'event' of your looking, happens to be captured or frozen in time on the window
pane/plate.

Now, when Barthes goes on to discuss the human
experience of viewing the photograph, the viewer of the photograph is separated from the
real woman in field - through time. So, when you look at
the photograph, your relation to the real woman in the
field is thus: viewer - relation of photograph to real woman - time -
real woman.

Perhaps I am
complicating this.  Think of it like a triangle: I (A) am the viewer. I point (look) at
someone (B).  B points at the real woman in the field
(C). B is the photograph.  When I look at a photograph, I am "pointing at
a pointing!"  In other words, I am looking at a single event of looking. Now, to grasp
Barthes' idea of contingency, imagine that the person (B), representing the photograph,
is invisible. And I can't point/look at (C) because I (A)
and the real woman (C) are separated by
time.