How to choose the right lenses for your cycling glasses

The tint of the lens determines how much light passes through the lens and protects your eyes from UV radiation and glare. All lenses fall into one of five filter categories based on their tint which is expressed as a category number from 0 to 4. The darkest tint belongs to category 4. Those lenses are suitable for extremely bright environments such as snow tours in high alpine regions. Category 3 and 2 are appropriate for average light situations from sunny to cloudy to rainy conditions. Categories 1 and 0 have a very light respectively transparent tint. They are adequate for darker environments such as gravel cycling or biking in the woods where minimal sunlight shines through the trees. Furthermore, the bright categories are suitable for rides at twilight, at night in the dark or cycling indoors, e.g. for track training. When lenses adjust their tint to the light conditions, they are called photochromic. Photochromic sports glasses are a good choice when the weather is rather unpredictable as they lighten to category 2 or even category 1 in darker conditions, or darken to category 3 in brighter conditions. So you always have a clear vision, no matter the environment.