Sunglasses Lens Categories 0-4 Explained: Which Tint to Choose
Sunglasses lens categories 0-4 explained: what each tint level means, which suits driving, beaches or snow, and how it differs from UV and polarization.
5 min di letturaDi IGIOO Optical
In questa storia
- 01What a lens category actually measures
- 02Categories 0 to 4 at a glance
- 03Which category suits everyday life?
- 04Driving: the category rules worth knowing
- 05Category, UV protection and polarization are three different things
- 06How lens colour interacts with category
- 07Prescription sunglasses and categories
- 08Frequently asked questions
- 09Pick the right darkness for your days outside
Sunglasses lens categories run from 0 to 4 and describe one thing: how much visible light the tint lets through. Category 0 is almost clear, category 3 is the everyday dark tint most people want for summer, and category 4 is for extreme glare such as high mountains and must not be worn for driving. The number tells you nothing about UV protection or polarization, so read those labels separately.
Below we break down each category, show where each one makes sense, and explain how to read the markings before you pick a pair.
What a lens category actually measures
Every tinted lens filters part of the visible light that reaches your eyes. The share that gets through is called visible light transmission, or VLT. A lens with 15% VLT lets 15% of visible light pass and holds back the rest.
The European standard for sunglasses (EN ISO 12312-1) sorts lenses into five filter categories based on that figure. You will often see the number printed on the inner temple as "Cat. 3" or simply "3", sometimes next to the CE mark.
- Lower number = lighter tint, more light through.
- Higher number = darker tint, less light through.
- The number is about brightness, not about colour, glare filtering or UV.
Categories 0 to 4 at a glance
| Category | Light let through (VLT) | Tint | Typical use |
|---|---|---|---|
| 0 | 80-100% | Clear or very light | Indoors, fashion tints, overcast evenings |
| 1 | 43-80% | Light | Cloudy days, city walks in weak sun |
| 2 | 18-43% | Medium | Spring and autumn sun, mixed light |
| 3 | 8-18% | Dark | Bright summer days, beach, holidays |
| 4 | 3-8% | Very dark | Glaciers, high altitude, intense snow glare. Not for driving. |
Which category suits everyday life?
For most people in Central and Northern Europe, a category 2 or 3 lens covers nearly every sunny day. Category 2 feels comfortable when the sun comes and goes, and you can step into a shop without taking your glasses off straight away. Category 3 is the classic summer choice: noticeably darker, calmer on bright pavements and sand.
If you only buy one pair, think about where you spend most of your outdoor time:
- Commuting and city errands: category 2 keeps contrast in shaded streets.
- Beach, lake or southern holidays: category 3 is the usual pick.
- Skiing above the tree line or glacier hikes: category 4, used only for that activity.
- Grey winter days or indoor style: category 0 or 1.
The Niloss C06, for example, comes with gradient green Cat.3 lenses, which puts it firmly in the bright-summer group.
Driving: the category rules worth knowing
Driving is where categories matter most. Category 4 lenses let through so little light that they are not suitable for driving at all; reputable sunglasses carry a warning for this. Categories 2 and 3 are the normal choice for daytime driving.
At dusk, at night or in tunnels, take tinted sunglasses off. Even a category 1 lens cuts light you need when it gets dark. If glare from wet roads bothers you during the day, a polarized lens in category 2 or 3 is often more useful than simply going darker. Our driving glasses collection groups frames that are designed with time behind the wheel in mind.
Category, UV protection and polarization are three different things
This is the most common mix-up. A dark lens is not automatically a protective one, and a light lens is not automatically weak.
- Category = how dark the lens looks and how much visible light passes.
- UV rating (such as UV400) = how much ultraviolet light the lens filters. It is listed separately from the category.
- Polarization = a filter that cuts reflected glare from water, glass and roads. It can be combined with different categories.
So when you compare pairs, check all three. Every frame page on IGIOO lists whether the lenses are polarized and whether they carry a UV400 rating. Browse polarized sunglasses if reflected glare is your main complaint.
How lens colour interacts with category
Two lenses in the same category can feel quite different because of their colour. Grey keeps colours closest to natural. Brown and amber warm the view and tend to make contrast look sharper on hazy days. Green sits in between. Gradient lenses are darker at the top and lighter at the bottom, so the category printed usually refers to the darkest part, not the whole lens.
Mirrored coatings reflect part of the light before it reaches the lens tint, which is why many mirrored lenses end up in category 3 even when the base tint looks moderate.
Prescription sunglasses and categories
If you need vision correction, you do not have to give up choice of tint. Prescription sun lenses are made to order, and the tint strength you choose decides which category they fall into. A practical approach is to match the category to your main use: medium tint for driving and daily wear, darker for holidays. See our prescription sunglasses and check the face shape guide to narrow the frame first.
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Frequently asked questions
Is category 3 too dark for everyday use?
Not on bright days. Many people wear category 3 all summer. If you often move between sun and shade, or live somewhere with lots of cloud, a category 2 lens may feel easier.
Can I drive with category 3 sunglasses?
Yes, in daylight. Categories 2 and 3 are the usual choice for daytime driving. Category 4 is not suitable for driving, and no tinted sunglasses should be worn at night.
Does a higher category mean better UV protection?
No. The category only describes visible light. UV filtering is rated separately, for example as UV400, so always check that label on its own.
Where do I find the category on my sunglasses?
Look at the inside of the temple arm. It is usually printed as "Cat." followed by a number, often near the CE mark. Product pages may also mention it in the lens details. If you are unsure, our FAQ page explains how to contact us.
Pick the right darkness for your days outside
Choose category 2 for changeable light and daily driving, category 3 for bright summer days, and keep category 4 for the mountains. Then check UV and polarization separately, and you will have a pair that suits how you actually live. Explore all sunglasses to find your shape. Add your prescription in a few clicks with our lens selector.
