Fill-in refers to a light source used in photography to illuminate the shadow areas of a scene. Its purpose is to reduce the contrast between the brightly lit and darker parts of an image, ensuring that details are visible throughout without flattening the overall lighting. Fill-in light can be provided by a secondary flash, reflector, or continuous light source, and it is often used in both studio and outdoor settings to balance natural or key lighting.
Understanding how to use fill-in light is essential for photographers seeking well-balanced, professional-quality images. Properly applied, it enhances detail in shadowed areas, improves overall exposure, and contributes to a more natural and visually appealing photograph without overpowering the primary light source.