In teaching us a new visual code, photographs alter and enlarge our notions of what is worth looking at and what we have a right to observe. They are a grammar and, even more importantly, an ethics of seeing.
To collect photographs is to collect the world. Movies and television programs light up walls, flicker, and go out; but with still photographs the image is also an object, lightweight, cheap to produce, easy to carry about, accumulate, store.
To photograph is to appropriate the thing photographed. It means putting oneself into a certain relation to the world that feels like knowledge -- and, therefore, like power.
Even when photographers are most concerned with mirroring reality, they are still haunted by tacit imperatives of taste and conscience. The immensely gifted members of the Farm Security Administration photographic project of the late 1930s (among them Walker Evans, Dorothea Lange, Ben Shahn, Russell Lee) would take dozens of frontal pictures of one of their sharecropper subjects until satisfied that they had gotten just the right look on film -- the precise expression on the subject's face that supported their own notions about poverty, light, dignity, texture, exploitation, and geometry.
In deciding how a picture should look, in preferring one exposure to another, photographers are always imposing standards on their subjects.