Sunglasses lens categories, from 0 to 4: which one under the Bali sun

Not all sunglasses filter the same amount of light. A small number, from 0 to 4, tells you how much. Under a tropical sun, knowing how to read it saves you a few bad surprises.

Between the beach, the scooter and shaded terraces, a single day in Bali takes your eyes through every intensity of light. Two pairs of sunglasses that look identical can feel very different, because they do not filter light the same way. That difference has a name: the lens category. Knowing it helps you pick the right pair for the right moment, and keeps you from mistaking a dark tint for real protection.

What the category actually measures

A sunglass lens category tells you how much visible light the lens lets through. The higher the category, the darker the lens and the more it cuts glare. The scale, harmonised across Europe, runs from 0 to 4. Do not confuse it with protection against ultraviolet light: the category is about comfort in bright light, not safety against UV. More on that just below.

The five categories in plain terms

Category 0 lets through 80 to 100% of light. Clear or very lightly tinted, it is mostly for looks, for clear prescription lenses and for indoors.

Category 1 filters roughly 20 to 57% of light. It suits overcast skies or the end of the day, when the sun is soft.

Category 2 holds back 58 to 82% of light. A good choice for medium sunshine, mid-season, or changing light.

Category 3 blocks 83 to 92% of light. It is the most common category and the one that fits the large majority of full-sun situations: beach, city, countryside, seaside.

Category 4 filters up to 97% of light. Reserved for extreme conditions such as water sports or high mountains, it is too dark for driving.

Category and UV are not the same thing

Here is the point most people miss: it is not the tint that protects your eyes from ultraviolet light, but the treatment on the lens. A very dark lens with no UV filter is actually deceptive, because it widens the pupil and lets in more UV. The real protection is called UV400: it blocks almost all harmful rays, whatever the tint. At Maison Mata, every sunglass lens includes UV400 protection, from the lightest to the darkest.

A good pair of sunglasses is judged not by its colour, but by the light it leaves for your eyes.

Which category for life in Bali

For most of your days here, category 3 is the sweet spot: dark enough for full sun, light enough to stay comfortable as you move from a shaded terrace to the beach. If you surf, sail or spend long hours on the water, where reflection nearly doubles the light, category 4 earns its place. For everyday, all-round use, one good category 3 pair is plenty.

And for riding a scooter

On the road, keep category 3. Category 4 is banned for driving and best avoided on two wheels, because it darkens your vision too much, especially when you enter a shaded stretch or ride under trees. For riding at night or in the rain, take the sunglasses off: no category is made for low light.

In short

The category number is not about protection, it is about how much light reaches your eyes. Choose category 3 for almost everything under the Bali sun, keep category 4 for water and extreme glare, and never rely on a dark tint alone: check for UV400 first, every time.

This article is general information and does not replace an eye exam or personalised advice from a qualified optician or eye-care professional.