Silhouettes are an effective -- and inexpensive -- way to enhance a scene's mood or atmosphere, infusing the scene with power, poignancy, beauty, romance, mystery, unease, or terror. This simple lighting technique can delineate a character or support a theme. Horror films have used silhouettes in many ways, as have other film genres and styles. Noir is especially famous for its heavy use of silhouettes.
Insidious: Chapter 2 makes admirable use of silhouettes.
Josh (Patrick Wilson) is a father possessed by a ghost. No one in his family knows this yet. The scene opens with Josh playing outside with his son. The smiling actors, joyful playing, and sunny lighting all suggest happy normalcy.
Josh's wife, Renai (Rose Byrne) gazes at her husband and son, happy and secure in what she sees.
Renai returns to her other son, still sitting at the breakfast table. The son relates an ominous story about Josh to Renai. Much of it is told in flashback. The son's story suggests there is something wrong with Josh. He might not be as he appears.
The son's story instills in Renai -- and in us -- a fear of Josh. This loving father of only a moment ago now seems to be a threat. Whereupon, Josh calls to them. They turn toward him and we cut to...
Josh, standing in the doorway -- in silhouette. He speaks in friendly tones. Yet the silhouette enhances the fear instilled in us by the son's story.
We cut to Renai and son, looking at Josh. Then again to Josh, the frame tightening from the previous long shot to a medium close-up. This has the emotional effect of strengthening Josh's presence, so that he feels that much more threatening.
This silhouette's emotional impact derives largely from the film's dramatic context. It is the son's ominous account to Renai, of seeing Josh behaving strangely, that infuses Josh's silhouette with menace. In another dramatic context, in another film's story, the silhouette might have an entirely difference impact, or no impact at all.
You might also want to read my previous post about Insidious: Chapter 2's use of sexual deviancy.
For more information on lighting and framing, see Horror Film Aesthetics: Creating the Visual Language of Fear. This blog represents a continuing discussion of my views on horror, picking up from where the book left off.