Dark Blonde Girl With Sunglasses Undresses Her Red Bikini At The Sea Shoreline

Sunglass lenses are made of either glass or plastic. Plastic lenses are typically made from acrylic, polycarbonate, CR-39 or polyurethane. Glass lenses have the best optical clarity and scratch resistance, but are heavier than plastic lenses. They can also shatter or break on impact. Plastic lenses are lighter and shatter-resistant, but are more prone to scratching. Polycarbonate plastic lenses are the lightest, and are also almost shatterproof, making them good for impact protection. CR-39 is the most common plastic lens, due to low weight, high scratch resistance, and low transparency for ultraviolet and infrared radiation.
Any of the above features, color, polarization, gradation, mirroring, and materials, can be combined into the lens for a pair of sunglasses. Gradient glasses are darker at the top of the lens where the sky is viewed and transparent at the bottom. Corrective lenses or glasses can be manufactured with either tinting or darkened to serve as sunglasses. An alternative is to use the corrective glasses with a secondary lenses such as oversize sunglasses that fit over the regular glasses, clip-on lens that are placed in front of the glasses, and flip-up glasses which feature a dark lens that can be flipped up when not in use. Photochromic lenses gradually darken in bright light.