Because the heyday of film noir occurred in the 1940s and 1950s, the primary identifying element of them is the fact that they were shot in black and white with an emphasis on low-key lighting. This results in a pervading darkness in film noir movies with many scenes obscured in shadow. On account of the themes common to film noir, many movies also depict a great amount of night scenes. Off-angle and deep focus cinematography are likewise frequent visual aspects of film noir.