Category 2 vs Category 3 Sunglasses: Which Do You Need?
Look closely at the arm or label of most sunglasses sold in the UK and you will see a number from 0 to 4. That is the lens filter category, and it tells you how dark the lens is. It is separate from UV protection: a lens can be any category and still block 100% of UV. Here is what the numbers mean.
The five lens categories
| Category | Tint | Visible light let through | Good for |
|---|---|---|---|
| 0 | Clear or very light | 80 to 100% | Fashion, overcast days |
| 1 | Light | 43 to 80% | Dull or changeable days |
| 2 | Medium | 18 to 43% | Everyday sun, UK summers |
| 3 | Dark | 8 to 18% | Strong sun, beaches, Mediterranean summers |
| 4 | Very dark | 3 to 8% | Glaciers, high mountains. Not for driving |
These bands come from the international sunglass standard, ISO 12312-1, and are used by the College of Optometrists in its guidance on tints and driving.
Category 2: the everyday lens
A Category 2 lens takes the edge off bright sun while keeping enough light for shade, cloud and indoors-outdoors moments. In the UK, where the light changes every half hour, that means you are less likely to keep taking them off. Folds use a Category 2 polarised lens that lets through 19.7% of visible light: towards the darker end of the band, so they still cope with a bright day.
Category 3: for strong sun
Category 3 is a popular choice for general sunglasses, and it is the better option if you spend long days on the beach, on the water or in southern Europe. The trade-off is that it can feel too dark on a grey British afternoon.
Can I drive in them?
In daylight, yes for Categories 0 to 3. Category 4 lenses are too dark for driving. At dusk or at night, the guidance is that lenses letting through less than 75% of light are unsuitable for road use. That rules out Category 2, 3 and 4 lenses, including Folds, and most Category 1 lenses too, so take your sunglasses off when the light starts to go.
Where does polarisation fit in?
Polarisation is separate from category. It cuts glare reflected from flat surfaces like water and wet roads, which makes a lens feel clearer and more comfortable without needing to be darker. That is why a polarised Category 2 lens can feel comfortable in conditions where you might otherwise reach for something darker.
So which should I choose?
For most people in the UK, a polarised Category 2 lens is the most useful everyday choice, with a Category 3 pair for holidays in strong sun. If you only want one pair that lives in your pocket year-round, that is exactly what Folds are designed for.
