Unger studied with the engraver Joseph von Keller at the Kunstakademie Düsseldorf from 1854 till 1858, when he moved on to the Munich Academy and followed the class of copper engraver Julius Thaeter for a year. In 1860 he was apprenticed to Franz Paul Massau, but became ill and depressed and returned to his parental home. After a period of travel he found work with the publisher E A Seeman in Leipzig, publisher of the newly founded Zeitschrift für bildende Kunst and engraved many plates for the art journal. In 1871 Unger was appointed a professor at the Grand-Ducal Saxon Art School. A decade later he settled in Vienna, to manage the University of Applied Arts. In 1894 he was named Professor of Fine Arts at the Munich Academy, where one of his students would be Ferdinand Schmutzer. He retired in 1908.

A compelling image of the Austrian composer Hugo Wolf (1860-1903), inspired composer of some 300 lieder, died young, and like Robert Schumann, in an asylum. Though the majority of Unger's prints are reproductive engravings, he did make original prints too, such as this portrait of Wolf.

Image size 36.8 x 26.6 cm. With an etched remarque of two staves from a four part Wolf song with the refrain “Nun gute Nacht” (Well, Good Night). On chine appliqué on wove, with thread to narrow margins.