Film noir tends to feature characters trapped in a situation and making choices out of desperation. Frequent themes are murder, betrayal, and infidelity. Films noirs tend to include dramatic shadows and stark contrast (a technique called low-key lighting).
The term film noir was coined by the French film critic Nino Frank and is derived from a series of hard-boiled fiction books entitled Série Noire. Films noirs were mainly shot in black-and-white in the United States between the early 1940s and the late 1950s. Many were low-budget supporting features without major stars, where 'moonlighting' writers, directors and technicians, some of them blacklisted, found themselves relatively free from big-picture restraints. Main features required a wholesome, positive message. Weak and morally ambiguous lead-characters were ruled out by the star-system, and secondary characters were seldom allowed any depth or autonomy. Flattering soft lighting, deluxe interiors and elaborately-built exterior sets were the rule. But Noir turned all this on its head, creating bleak but intelligent dramas tinged with nihilism and cynicism in real-life urban settings, and using unsettling techniques like the confessional voice-over or hero's-eye-view camerawork. Gradually the noir style re-influenced the mainstream it had subverted. Orson Welles' Touch of Evil is often referred to as the last "classical" film noir.
Almost all film noir plots involve the hard-boiled, disillusioned male (usually in the form of a private eye) and the dangerous femme fatale. Usually because of sexual attraction or greed, the male commits vicious acts, and in the end both he and the femme fatale are punished or even killed for their actions.
These characters are derived from 1930s gangster films and, more importantly, from pulp fiction magazines such as The Shadow, Dime Mystery Detective and The Black Mask. Books by the Black Mask writers Dashiell Hammett (The Maltese Falcon) and Raymond Chandler (The Big Sleep) became two of the most famous films noirs.
The aesthetics of film noir are heavily influenced by German expressionism. When Adolf Hitler took over Germany, many important film artists were forced to emigrate (among them were Fritz Lang, Billy Wilder, and Robert Siodmak). They took with them techniques they developed (most importantly the dramatic lighting and the subjective, psychological point of view) and made some of the most famous films noirs.
Another important influence came from Italian neorealism. After 1945, film noir adopted the neorealist look and scenes were shot on real city locations (not in the studio).
In the 1960's American filmmakers like Sam Peckinpah, Arthur Penn and Robert Altman created genre films that broke the strict format of the genre's rule to convey social and political messages. In The Long Goodbye Altman's hard-boiled detective is represented as a hapless bungler who can't help but lose the "moral battle".
The genre has been parodied (both ruthlessly and affectionately) on many occasions, the most notable examples being Steve Martin's black and white "cut and paste" homage Dead Men Don't Wear Plaid, and Woody Allen's Play It Again, Sam. Many of Joel and Ethan Coen's films are excellent examples of modern films influenced by the film noir genre - especially Blood Simple, the title itself lifted from the Dashiell Hammett story Red Harvest.