What is the primary function of a lens hood in photography?

The primary function of a lens hood is to reduce lens flare and improve contrast in photographs. Lens flare occurs when unwanted light enters the lens, often from a bright source outside the frame, which can lead to a decrease in image quality. A lens hood helps to physically block this stray light from hitting the lens elements, allowing for a clearer image with better contrast and saturation. By doing so, it also ensures that more of the light intended for the photograph is captured, enhancing overall image quality.

While there are other benefits to using a lens hood, such as some degree of protection for the lens from impacts and scratches, or reducing moisture and dust from reaching the front element, these are secondary functions compared to its primary role in improving image clarity and reduction of flare.