Eyes so turned than they show a large glint of white suggest one of the subversive emotions—suspicion, jealousy, flirtation, or fear, and they should not be so displayed unless some such thought is meant to be conveyed (Figure 16). In portraits it is usually essential that the eyes be shown; but in pictures with the emphasis on the plastic qualities, particularly in nudes, an advantageous impression of impersonality is gained by downcast eyes.

William Mortensen, The Model: A Book on the Problems of Posing (1937), p. 34