Faces in the everyday impress us as hives of subtlety. That impression must be sharpened in photography, which discloses only a microsecond of the face's behaviour, immersed in a social process.

Though infested with many bewildering anomalies, photographs are considered our best arbiters between our visual perceptions and the memory of them. It is not only their apparent 'objectivity' that grants photographs their high status in this regard, but our belief that in them, fugitive sensation has been laid to rest.