Lower the contrast of the images, and avoid the surrounding interference light entering the lens during light photography or night photography.
In the case of backlighting, sidelight or flash photography, it prevents the entry of non-image light and avoids smog; in the case of smooth and side-light photography, it avoids the scattered light entering the lens.
Provides protection from unwanted light dazzling and accidental damages.
It can also prevent fingers from accidentally touching the surface of the lens, and can also block the wind, sand and rain to some extent.