Category 4 sunglasses have dark lenses for use in extreme sun conditions where high glare or intense sunlight is experienced. Category 4 lenses let in less than 8% of light – this makes them suitable for activities like skiing, mountain climbing, high altitude hiking and desert trekking. Also available are photochromic sunglasses (light adjusting) with lenses that darken to category 4 in intense sun/high glare conditions. Category 4 lenses are also suitable for eyes that are very sensitive to sunlight. Lower down the page is more information about lens categories.
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The lens tint category number for eyewear equates to a percentage of the VLT (Visible Light Transmission) – basically how much light the lens lets through, as follows:
- Category 0: 80-100% VLT
- Category 1: 46-79% VLT
- Category 2: 18-45% VLT
- Category 3: 8-17% VLT
- Category 4: 3-8% VLT
The following is a general guide to the Categories that apply to different lens colours:
- Category 0 – Clear lens, light yellow & very pale tints
- Category 1 – Yellow, pale orange & light amber
- Category 2 – Orange, rose, red, amber & light brown
- Category 3 – ‘Standard’ grey & brown sunglass lenses
- Category 4 – Dark grey & brown sunglass lenses
Almost all the grey and brown lens sunglasses sold on the Sunglasses For Sport website are Category 3 and suitable for use in strong sun conditions. Category 4 lenses are always clearly identified because they have specific uses e.g. high altitude walking, climbing and skiing. They are also good for anyone that has eyes sensitive to bright light but it’s important to know that you mustn’t use Category 4 lenses for driving (they are too dark for driving and could invalidate your car insurance if worn while driving).