VLT is a measurement that specifies the percentage of light coming through the lens reaching your eyes. A clear lens for dark conditions have around 90% VLT and a very dark colored lens with mirror for sunny conditions may have down to 5% VLT. Most all round lenses have between 30 – 50 %. POC goggles have alternatives for all kinds of conditions. Please note that the VLT for one tint can differ a bit if the lens has a single or double construction and if it has a spherical or cylindrical shape.
The color spectrum runs from blue to red with a lot of different shades in between. The color sensation and perception will differ between individuals and due to this the choice of lens color will is to an extent a subjective matter. One basic rule explains the contrast enhancing effect by studying the color spectrum.
When choosing a lens with yellow, orange, pink or red color it blocks out more of the blue end of the color spectrum. This enhances contrast, enabling you to make out shapes, objects and bumps in the snow more clearly. These lenses work well in low light, fog and flat light, but also in moderate light. However some individuals experience good contrast by blocking the other end of the spectra as well, by using a blue tint.
In bright light, dark tints will keep your eyes more comfortable. There is also the possibility of choosing a brighter tint but with mirror coating to block some of the light to keep your eyes comfortable. Some individuals experience green as a good lens color since it will dampen the color spectrum evenly, the colors will be experienced as they normally do appear.