Which light source is used to soften deep shadows?

Fill light is specifically designed to soften deep shadows created by the main light source, often referred to as the key light. In a typical lighting setup, the key light establishes the primary illumination and often creates shadows due to its angle and intensity. The fill light is added to counterbalance these shadows, making them less harsh and creating a more even exposure across the subject. This technique helps to maintain detail in shadow areas, contributing to a more balanced and aesthetically pleasing image.

In comparison, backlight and hard light serve different purposes; backlight is primarily used to create separation from the background, and hard light generates distinct, well-defined shadows that are often more dramatic and less flattering for revealing details in darker areas. This makes fill light a vital tool in cinematography and photography to ensure shadows remain soft and natural in appearance.