Otto Dix(1891-1969), contrary to many portrait painters stressed the importance of first impressions preferring to paint strangers. He is quoted as saying, "You know, if one paints someone's portrait, one should not know him if possible." It's an interesting approach and in his portraits, there is exaggeration, miniaturisation, and caricaturisation of his first impressions enveloped in the style of the Old Masters.
"Everybody thinks they know what art should be. But very few of them have the sense that is necessary to experience painting, that is the sense of sight, that sees colors and forms as living reality in the picture. "
Otto Dix (.org)
Otto Dix Wiki
Otto Dix (Mess.net)