The styles and coventions of typical Film Noirs...

Noir films tend to reflect certain themes. Unlike most other genres, there is some argument about what constitutes film noir. Films are often described in terms of how noir they are.It should be noted that Film Noir movies also normally fall into other genres, for example most Film Noir films are also thrillers. 

The following are all typical conventions of Film Noir movies, few if any contain all of these conventions, yet they are all trademarks of the film noir style:

•  The Look - Black and white, often high contrast. Much given to close-ups. People, especially femmes fatales, tend to face the camera while talking to people behind them. This allows the camera to dwell stylishly on their reactions and their cigarette smoke.
  
•  The Women - A femme fatale (literally 'killer woman') is the beautiful yet manipulative love interest, who often turns out to be the villain of the piece. This ambiguity is often central to the plot. Invariably chain-smokers. There may also be a saccharine 'good' woman. She will be recognisable as she will not smoke.
  
•  The Men - Often Private Investigators (PIs). Usually get hit lots, may have a way with women. Always carry guns. Usually heavy drinkers, invariably chain-smokers. If they have a foreign accent, they will be villains. Alternately, they may be the wealthy-but-dull (and thus doomed) husbands married to the femmes fatales.
  
• The Plots - Often complex. The usually innocent hero is caught up in a web of intrigue he doesn't fully understand, possibly woven by the femme fatale. Books by writers like Dashiel Hammet and Raymond Chandler (both smokers) were favourites. 
  
• The Cars - Huge American things with more solid steel than a Sherman tank. They look like 'The Mini That Ate New York'. They never smoke, even when shot or run off the road. 
   
• The Philosophy - In a word, bleak. Life is cheap and money is hard to come by except by crime, which definitely does pay. This owes a great debt to the influence of the European directors who had recently arrived from war-torn Europe, with a much more cynical world-view than most of their American colleagues.
  
• Expressionism - Always big in Europe, this style now invaded the Hollywood mainstream. It involved using visual means to express characters' feelings - the emotionally distant might be physically separated, for example, or powerful characters might loom over the camera or be physically higher than weaker characters. This was also used to imply a sexual relationship, particularly a homosexual one, thus circumventing the strict morality of the Production Code guidelines of the time. 
  
• The Service Station - There are only two places in noir America; the crime-ridden city or the small-town garage/motel/restaurant. Whether it's a valuable piece of real-estate or a simple refuge for someone hiding from his past life, drifters always seem to end up working there.