His father, also named Karl Friedrich Lessing (1778–1848), was a judicial officer in Wrocław, from 1809 on the chancelor of the court of the Free State country of former Polnish-Wartenberg (Wartenberg in Poland).

After spending two years at a Catholic school in Breslau, his talent for drawing was noted by the artist, Johann Heinrich Christoph König [de] who, in 1822, arranged for him to study at the Bauakademie in Berlin.

A successful showing in 1825, with the subsequent sale of the painting Kirchhof mit Leichensteinen und Ruinen im Schnee (Churchyard with Gravestones and Ruins in the Snow), reconciled his father to his chosen career.

In the first phase of his career, he painted dark and imaginative landscapes, after the style of Caspar David Friedrich with romantic motivs like castle ruins, left churchyards (Klosterhof im Schnee, 1829, Wallraf-Richartz-Museum, Cologne), or ragged rocks, with staffage figures of monchs, knights, robbers, or gypsies.

[2] He completed part of a monumental representation of the Battle of Iconium, but decided that wall painting did not appeal to him, and allowed another artist at the project, Hermann Plüddemann, to finish the fresco, from his sketches.

[3] The picture went on tour throughout Germany and France[4] and was positively discussed, as, for instance, by Friedrich Theodor Vischer in his essay "Zustand der jetzigen Malerei" (1842).