What traits of the duchess's portrait are pointed out by the duke?
The Duke begins by describing the Duchess as looking as though she were alive. This foreshadows his "collector" attitude. Whether the Duchess is framed or alive, she was an object he collected rather than a person for whom he had deep romantic feelings. He describes the depth and passion of her glance as bestowed universally rather than his alone. At first this suggests that she was fickle; later we understand that it is his own possessiveness speaking. The portrait is obviously smiling, but the Duke has stopped all her smiles (probably by murdering her), and thus the lifelike smiling image that is repeated as he moves on to point out Neptune asserts that she is most strongly present in the poem when caught in the timeless immobility of a portrait.