Lens hoods are designed to prevent unwanted stray light from entering the lens. They do this by extending and shading the end of the lens and since the end of the lens is extended, you also achieve the added benefit of some extra protection from accidental impact. In the backlight, side light or flash photography, to prevent the entry of non-imaging light to avoid the fog. Frontlighting and side light in photography to avoid scattering light entering the lens around. In light photography or night photography, you can avoid the interference of light into the lens around.