This constellation is the most basic form of lighting arrangement used in filmmaking and is used to present characters or subjects to their best advantage. The three light sources involved are called the key light, fill light and backlight. The strongest light source is the key light, which directs the viewer’s attention. The fill light – less bright than the key light – softens the borders between lit and shady areas, while the backlight is used to set the subject off from its background. For related information, read the entries concerning key light, fill light and backlight.