Sunglass lenses are graded by how much visible light they let through. The grade is called the filter category, a number from 0 to 4 that is often printed inside the temple. Knowing it helps you pick the right pair for the day ahead.
The five categories
- Category 0: clear or very light tint. Fashion and indoor wear.
- Category 1: light tint for overcast, grey days.
- Category 2: medium tint for everyday sun.
- Category 3: dark tint for bright sun. The most common grade for sunglasses.
- Category 4: very dark, for snow and high altitude only, and never for driving.
What TIEFE uses
Most of our frames carry a dark grey Category 3 lens. Grey turns brightness down evenly, so colours stay close to true. BERNSTEIN uses an amber-brown Category 2 lens instead. It lets a little more light through and warms the view, which many people like on hazy afternoons. You can see the grey version in action on KREIS.
Tint is not the same as UV filtering
A darker lens does not automatically block more ultraviolet light, because UV filtering is a separate property of the lens. Every TIEFE lens is made with a UV400 filter, so check for that label when you compare any pair, not just the darkness.
After dark
Tinted lenses reduce the light reaching your eyes. That is the point in daylight and a problem at night. Do not drive at night or in low light with any tinted sunglass lens, whatever its category.
This article is general information, not medical advice. If you have an eye condition or need prescription lenses, please speak to an optometrist.
