I sort of feel that the role of a portrait in society is to represent the sitters, we see paintings of Shakespeare and we believe that it is what he looked like, well maybe a little older, fatter and with a higher hairline. I guess it would be cool if the portraits that were painted really did look like the sitter or expressed some sort of emotion that gave the viewers in the future a sense of the sitter's pathos at the time it was painted.
