Combine fill flash with ambient light by using a slower shutter speed, ensuring both light sources blend seamlessly. Experiment with different angles and settings to find the most flattering and natural-looking illumination for your subject. Fill flash, on the other hand, uses a quick burst of light to brighten shadows and balance exposure in bright, contrasty scenes. If your ISO is 100, and you have the camera in aperture preferred mode and choose f/8 for enough depth of field for a group shot, your shutter speed would be 1/200th of a second for the ambient light. Backlit subjects turn into silhouettes, and overcast days flatten portraits into lifeless, grey images.