"As Peggy Phelan describes in 'The Unmarked', posing for a portrait is a process whereby one performs an identity that one believes others expect to see. Uncertain about what the body looks like or how substantial it is, we perform, Phelan says, "an image of it by imitating what we think we look like. We imagine what people might see when they look at us, and then we try to perform (and conform to) those images. . . The imitative reproduction of the self-image always involves a detour through the eye of the other." Ideally, artist and sitter collaborate to produce an image that reflects what the sitter hoped to project to the world. However, in some cases, as in Brant's, the sitter has less control over the artist's rendering of an image, as he or she is not the patron, the one, because paying for the portrait, whom the artist must ultimately please."
From 'Picturing Imperial Power: Colonial Subjects in Eighteenth-Century British Painting' (1999), by Beth Fowkes Tobin