Sunglasses can be divided into 5 categories depending on the UV filter. Each number corresponds to a light transmission. The higher the number, the less light transmission occurs and the darker the lenses are. Typically, the category is stated on the glasses arm or on a sticker on the lens.
Category 0 – light transmission 80–100% • Colourless or very light
filter. Typically sport or protective glasses designed to protect against
dust or debris, but not against sun.
Category 1 – light transmission 43 – 80% • Very lightly coloured
lenses, usually yellow or orange, suitable for weaker sun radiation or as wind
Category 2 – light transmission 18 – 43% • Medium dark filter
suitable for medium sun radiation and for casual wear. Their tint is slightly
than usual. Can be used for spring and autumn walks on sunny days. They will also come in handy
while driving and frequently moving between shade and sun.
Category 3 – light transmission 8 – 18% • Dark filter suitable for
intensive sun radiation on the beach or in the city. This category is typical
most types of sunglasses. It is perfect for summer because it provides a higher degree of protection
against sun radiation than the previous category.
Category 4 – light transmission 3 – 8% • Very dark filter for very
intensive sun radiation. Sunglasses for mountains or desserts and everywhere
where the sunshine is not just extremely strong, but where it also reflects a lot. These sunglasses can’t
be used for driving.