It’s the last week to see the Met’s exhibition of Renaissance portraits, on view until March 18th.  It is a splendid show that traces the evolution of portraiture in the 15th Century from a standard format to more realistic depictions.  Towards the middle of the 1400s the subjects of the paintings came to have a more life-like, vital appearance.  Rather than being simply idealized representations, the sitters showed expression and were often painted with negative qualities – physical and spiritual – visible.  Perhaps most impressive are some of the marble busts on view:  the sculptures show features that are amazingly expressive and, in the case of Desiderio da Settignano’s “Bust of a Young Woman,” enchanting.