Whether you're on an 8,000 m summit, in the midst of a race out on the open sea or holidaying down at the beach, good protection against the sun is essential whenever you're outside. According to your use, there are different filter indices or sun protection categories for your eyes. We help you to see more clearly. WHAT DO SUNLENSES PROTECT OUR EYES AGAINST? When we're exposed to the sun, our eyes' pupils contract to filter sunlight before it reaches our retina. In certain situations, this natural filter isn't enough. Sunlenses must protect us against: INVISIBLE LIGHT Ultraviolet light: which is highly damaging to the eye. While UVA radiation is less dangerous, UVB causes burning and numerous symptoms affecting vision. infra-red radiation can be dangerous for the eyes in extreme conditions (high mountains, desert, etc.), causing dehydration and overheating. So protecting your eyes using lenses that block 100% of UV radiation is essential. VISIBLE LIGHT The dangers posed by visible light include glare, fatigue, interference and a possible temporary reduction in vision. This light doesn't always have the same intensity according to the weather, climate, terrain, etc. which is why there are different filter indices or protection categories to protect your eyes against these dangers. WHICH FILTER INDEX AND/OR LENS CATEGORY SHOULD YOU CHOOSE? There are five categories rated on a scale from 0 to 4, based on the ascending percentage of filtered light. The filter index or sun protection category is pretty much the same thing, both are determined by the quantity of visible light that they let through the lens. The lower this transmission, the darker the lens and it's this tint that affects glare but not UV radiation. If you're looking for versatility, we recommend category 3 that is well suited to all light conditions. In addition to the category, it's also important to take account of lens colour, which affects your comfort, and the type of material in terms of their optical quality. Coding Category Lens tint Indication Use / Time Transmission rate A 0 Clear or very lightly tinted lens Comfort, aesthetics Interior, night 80 to 100% AB 1 Lightly tinted lens Low light levels Bad weather 43 to 80% B 2 Moderately tinted lens Average light levels Average sunshine 18 to 43% C 3 Dark lens Strong light levels Very strong sunshine 8 to 18% D 4 Very dark lens Exceptional light levels Extreme exposure 3 to 8% /!\ Category 4 lenses are not permitted for driving as they filter out too much light. To conclude, watch out for preconceived ideas: it's not because your lenses are dark that you'll be protected against UV! Tinting only affects visible light. Before buying anything, make sure that the European CE standard and the reference 100% UV400 are featured on your sunglasses: these require manufacturers to meet construction and performance requirements to offer you lenses that block all light rays with a wavelength of 400 nanometres, which covers all UV rays. At Julbo, all our lenses are optical class 1 and guarantee 100% protection against UVA, B and C.