The use of lighting and the way that it casts shadows on certain characters plays an important role in Double Indemnity. Shadows are not always used to mean the same thing. Lighting is used in Double Indemnity to communicate many different ideas to the audience. One way shadows or darkness is used is to hint at impending violence or evil action.
In the picture above, not only is the room itself very dark, but there is also the distinct shadow of Neff on the wall in the background. In the scene that follows this still shot, both Neff and Phyllis shoot one another and it is the ultimate downfall of both characters. The use of lighting in this picture is hinting at what is about to happen. Another way lighting is used is to show that there is a darkness within a character or that they are thinking of doing something criminal.
In the picture above of Phyllis, there is clearly a dark shadow across her face that is a stark contrast from the rest of the frame. This shadow is used along with the mischievous look on her face to show that she is contemplating something we don't know about, and it is probably not a good thing. Knowing the ending of the movie, she is probably realizing that she has planned everything out perfectly and that she is going to get what she wants. The shadow across her face is an attempt to communicate that to the audience.
In the picture with Neff, There are striped shadows being cast on him from the venetian blinds on the windows. This gives the idea that he is a criminal in someway, as it looks like he is wearing a striped prison jumpsuit. Although he has not done anything criminal yet, this image could be trying to say that, with the influence of Phyllis-he is in her living room-Neff becomes somewhat of a criminal. Her power over him can force him to do things that he would not normally do even something illegal. All of that is implied through the striped shadows on his suit. While it is something easy to overlook, the use of lighting and shadows can have great significance in a film.
