VLT: How Goggles filter light
Goggles are identified by a number called VLT which indicates how much sunlight is allowed to pass through.
The amount of light a goggle lens allows to pass through is called Visible Light Transmission (VLT). VLT is expressed as percentage of light allowed through the lens falling somewhere between 0% and 100%.
At SwissCorps, under our philosophy of one all-purpose item for each deployment, we recommend a VLT of 30% to 50%, which is found in our core SkyGaze product line.