The painter constructs, the photographer discloses. That is, the identification of the subject of a photograph always dominates our perception of it—as it does not, necessarily, in a painting. The subject of Weston’s “Cabbage Leaf,” taken in 1931, looks like a fall of gathered cloth; a title is needed to identify it. Thus, the image makes its point in two ways. The form is pleasing, and it is (surprise!) the form of a cabbage leaf. If it were gathered cloth, it wouldn’t be so beautiful. We already know that beauty, from the fine arts. Hence the formal qualities of style—the central issue in painting—are, at most, of secondary importance in photography, while what a photograph is of is always of primary importance. The assumption underlying all uses of photography, that each photograph is a piece of the world, means that we don’t know how to react to a photograph (if the image is visually ambiguous: say, too closely seen or too distant) until we know what piece of the world it is. What looks like a bare coronet—the famous photograph taken by Harold Edgerton in 1936—becomes far more interesting when we find out it is a splash of milk.