One of the most potent film genres in terms of subsequent influence was the so-called film noir, so-called because no one making a film noir at the time of its creation and ascendance ever used the term or even assumed that they were working in a genre or style that might deserve a name of its own. the term was applied long after by French critics who noticed a stylistic shift in American films in the 1940s, and as Thomas Schatz notes, this style dominated films in the late 1940s and early 1950s to such a degree
that it came to identify both the narrative-cinematic style of those films and also the historical period during which they were produced (Schatz 112).
The style would have an influence long after that historical period ended. Indeed, it continues to have an influence today, though the underlying social dynamic that produced it in the first place changed long ago. Yet, there is something in the film noir that appeals to and expresses darker aspects of the human soul and so has a resonance still. A comparison of In a Lonely Place (1947) and Blade Runner (1982) will show how the style changed and how it was used differently in the two time periods.
Film noir is more properly called a style rather than a genre:
Film noir was itself a system of visual and thematic conventions which were not associated with any specific genre or story formula, but rather with a distinctive cinematic style and a particular historical period (Schatz 112).
Schatz's insistence on noting the relationship to a historical period is important because it indicates that film noir was a social, psychological, and aesthetic response to a certain sense of societal angst that developed first in the uncertainties of World War II, a period of world tensions manifested in the psychological ambiguities of film noir, and then continued in the new uncertainties of the Cold War period, especially in the years immediately after World War II when ...