His grandfather, Diderik von Cappelen (1761–1828), was member of the Norwegian Constituent Assembly at Eidsvoll in 1814.
[4] Cappelen was a student at Kunstakademie Düsseldorf under Johann Wilhelm Schirmer in landscape painting class from 1846 to 1850.
Cappelen went on several study tours in Norway: the Gudbrandsdalen and Lom (along with Gude and Johan Fredrik Eckersberg, 1846), Sogn and Hardanger (1847), as well as several summer residence in the countryside around Holden.
His wild designs from Telemark with forests, lakes and streams are filled with a pathetic mood of loneliness and transience.
Powerful forms of nature, especially trees and mountains block, is effective in the composition, coloring and playing in the deep moss green tones.