Sunglass Lens Categories 0 to 4, Explained
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Sunglasses sold in Europe are marked with a filter category from 0 to 4. The number describes how much visible light gets through the lens. It tells you nothing about UV protection, polarization or build quality. It tells you how dark the lens is, which is the first thing to check when you choose a lens for a specific place and light.
The five categories
| Category | Light let through | Use |
|---|---|---|
| 0 | 80–100% | Clear or very light tint. Comfort and protection from wind and debris, not from sun. |
| 1 | 43–80% | Light tint. Low or flat light, dawn and dusk, heavy cloud. |
| 2 | 18–43% | Medium tint. Average sunlight and mixed conditions. |
| 3 | 8–18% | Dark tint. Bright sun, water, beach, mountains in summer. |
| 4 | 3–8% | Very dark. Glaciers, high altitude, intense snow reflection. Not for driving. |
The ranges come from the European standard EN ISO 12312-1, which replaced the older EN 1836. The category ranges themselves stayed the same.
Which category for which place
On the water. Water reflects sunlight back at you, so light arrives from above and below. Category 3 is the standard. All our watersport sunglasses use it, and several offer a photochromic version that moves between category 1 and 3.
On snow. Fresh snow reflects far more light than water, and UV gets stronger with altitude. Bright days call for category 3; flat light and snowfall call for category 1 or 2. That range is why photochromic ski goggles make sense.
On the road and the trail. Category 3 for sun. Lighter lenses for forest trails, dawn rides or cloud.
In the city. Category 2 or 3. Every frame in our Fashion range is category 3.
Driving
Categories 0 to 3 are suitable for daytime driving. Category 4 is not, and has to be marked as unsuitable for driving. At dusk and at night the standard calls for lenses that let through more than 75% of light, which in practice means clear or near-clear lenses only.
Photochromic lenses react to UV, and most windshields block it, so they stay lighter behind the glass than they would outside.
Darkness is not protection
A clear category 0 lens can block 100% of UV. A dark lens with poor UV filtering is worse than wearing nothing, because your pupils open wider behind it and let more UV in. Check both. Every Ocean lens blocks 100% of UV, whatever its category.
Next: what polarization adds, and how photochromic lenses work.