Fill flash is a photography technique that is used to illuminate the darker areas of an image. Fill flash can iron out unwanted shadows in your pictures. Fill flash is supplemented to correctly expose the subject. It is good to use when your picture is overexposure. Using fill flash and a reflector can ramp up the glow of the subject’s face. You have to adjust your fill light to the natural light. Fill flash can come in handy to take out the minute details of the shots. To use fill flash and you use a pop-up camera flash, you will have a flash mode called “Fill in”. The mode can be selected either from an on-camera button or from the menu. A major problem you will encounter while using fill flash is when ambient light is behind the subject. In order to derive the best upshot, you can go for a 30% flash and 70% natural light.