Photochromic lenses are the best the all-round option and work in almost every condition from low light overgrown rivers to bright sunshine. Photochromic lenses darken on exposure to UV radiation. Photoflite series lenses start very light and darken very linearly when UV light is increased. NOTE: Photochromic lenses are not a good option for driving a car as the UV light does not penetrate the car windshield and lenses will not darken in bright sunlight.