The S1784 Hellfire LTD Lens is 17% Dark and 84% Clear. The Hellfire Lens starts off clear and transitions to dark according to environmental conditions.
Popular with special forces due to their ballistic properties making them perfect for air and ground operations.
Great for motorcycle riders as the amount of transition allows riding day and night with the same pair of glasses.
The science behind what makes a photochromic lens transition from light to dark is quite simple. There is a chemical reaction that occurs when a photochromic lens comes into direct or inadvertent contact with UV rays. The stronger the UV rays are, the darker the lens will transition. If there is limited exposure to the sun's rays, then the lens will not fully transition. Instances when this will occur will be inside a vehicle or behind a full face helmet that has a UV filtering laminate. The temperature and elevation can affect the way that the photochromic lens changes as well.