Sternen was a draughtsman, restorer, graphic artist and art teacher, but primarily a virtuoso painter in terms of technique. He was the only one of Slovenian Impressionists to have finished art academy, namely in Vienna. He also lived in Munich for some time and attended the Ažbe art school. He became renowned as a painter of female figures; prevalent in his output are nudes but he also painted portraits and cityscapes. His painting principles were based on objective observation of his subject matter and not on emotional participation in it, and he revealed himself as an Impressionist in his handling of visual effects, dynamic framing of the scenes and impasto application of paint.