What kind of subject is fill flash most useful for?

Fill flash is particularly effective for subjects against a bright background because it helps to illuminate the subject that would otherwise be in shadow or underexposed due to the strong ambient light behind them. When photographing a subject such as a person outdoors on a sunny day, the light from the sun can create harsh shadows on the face or body. Utilizing fill flash in this scenario allows the photographer to balance the exposure, ensuring the subject is adequately lit without losing details due to overexposure in the brighter areas.

In contrast, other scenarios may not benefit as much from fill flash. For instance, in low-light environments, the primary goal is often to enhance the overall exposure without the need for additional flash. Similarly, subjects that are brightly lit by the sun are already well-exposed, minimizing the benefit of added flash. Lastly, subjects that are mainly black may not require fill flash because their color absorbs light, making it less effective in this context. Thus, using fill flash against a bright background facilitates a more balanced and visually appealing image.