He worked in a variety of media, including painting, sculpture, graphics, ceramics, photography, and film, and was also a mountaineer and an author.
Guðmundur studied art in Iceland in 1911-13 (with Stefán Eiríksson) and 1916 (with Ríkarður Jónsson and Þórarinn B. Þorláksson), in Copenhagen in 1919-20 and in Munich in 1920–25.
[1] He worked in media including graphics, watercolors and oils, sculpture, glass, copper, silver, and ceramics as well as photography and film.
[2] He also designed jewelry, furniture, gardens, and houses and wrote books, including poetry and the 1946 Fjallamenn, illustrated with his photographs.
They subsequently divorced, and he remarried to her daughter Lydia Zeitner-Sternberg, a ceramicist who had come to Iceland in 1929 and was the mother of his son Einar.