Sontag says...

"Photographs furnish evidence."
from, 'On Photography' (1973) Dell Publishing.

Sontag's essays on photography most brilliantly sum and examine several aspects of the photographic medium; too much to fully discuss here, but lets look at a few key points in relation to that 'evidence'.

By furnishing evidence, she observes the notion of redefining reality. The medium represents our world with a kind of realism that we expect to convey the truth. It proves we went somewhere, saw, and that something happened or just is. And even if we didn't capture it ourselves, we can acquire and consume the experience through publications, online, through broadcast, or as fine art prints to hang on the wall. We all get to experience what was captured in that photograph whethor we were there or not.

Photography is about much more than just the act of recording a reflection of existance. It is more than just a medium used to represent two dimentional illustrations of reality. Yes, a photograph is evidence of what existed at a moment in time... it is also evidence that someone was there to make that image and because of this, according to Sontag, we all have the option of experiencing something from the comfort of our living rooms:

'On Photography' page 162: " As the taking of photographs seems almost obligatory to those who travel about, the passionate collecting of them [or consumption of them, ie: by looking at a blog regularily] has special appeal for those confined- either by choice, incapacity, or coercion-- to indoor space. Photograph collections [or consumption] can be used to make a substitute world... For stay-at-homes, prisoners, and the self-imprisoned, to live among the photographs of glamorous strangers is a sentimental response to isolation and an insolent challenge to it.... To possess the world in the form of images is , precisely, to reexperience the unreality and remoteness of the real."