His film career diminished during World War II and he also worked rarely as a cinematographer after the war as well.
The cinematographer Karl Hasselmann learnt the profession of a mechanic and he joined the film business in this function when he got a job in a repair shop for cinema equipments.
Karl Hasselmann only continued his film career after the end of the war and he was engaged again as a cinematographer for many productions in the 20s.
His experiences as a cinematographer were also regularly used in the 30s.
When the fictitious film became a more and more important factor in the film business Karl Hasselmann became a demanded cinematographer and he realised till to he beginning of World War I numerous movies.