A focusing hood is a light-proof cowl used on twin-lens reflex (TLR) cameras and most roll-film SLR cameras to shield the focusing screen from stray or extraneous light. This helps the photographer see the image on the screen more clearly and achieve precise focus.
Focusing hoods are especially important in bright conditions or when working outdoors, as they prevent glare and reflections from interfering with composition and sharpness. By improving visibility on the focusing screen, they allow photographers to accurately frame and focus their shots, ensuring professional-quality results.