There are, of course, many criteria by which one can judge a photograph: form, composition, color, subject matter, context, or the viewer’s emotional response. In viewing Harry Benson: Being There, currently on display at Donald W. Reynolds Center for American Art and Portraiture at the National Portrait Gallery, it is not Benson’s technical ability as a photographer that impresses, but his uncanny ability to be present when historic moments occur and then place himself…