Photochromic (PC) lenses are available in some select lens colors. The PC lens changes tints according to how dark or bright it is outside, allowing you to see better as light conditions change.
Smith Optics use Techlite Lens; Glass is #1 for optical clarity & scratch resistance. Give it a specialty TLT grind to reduce the weight and you've got yourself the world's lightest Techlite glass lens. Chemically treated to increase shatter resistance. ANSI Z80.3 surpassing impact resistance and prismatic power. 100% UVA/B/C. Perfect for low impact hyperactivities and loitering with intent.
Visible Light Transmission (VLT) is the percentage of available light allowed to reach the eye. Different lens tints offer specific VLT to enhance vision in different light conditions.