Untiring, photosensitive molecules are at work here! The light-sensitive particles help the lens show off its unique talent: in sunlight, the surfaces of these photosensitive molecules increase, causing the lens to darken, and they do so more intensely depending on how strong the sun and UV radiation is. This way a suitable – and comfortable – tint intensity is achieved no matter how bright it is. Whenever you're inside or there's little UV radiation, the molecules 'fold' again and the lenses clear up, ensuring optimum vision indoors.
The basis for this transformation is a simple chemical reaction which was discovered back in the 1960s and has been continuously improved up through the present day. You can recognise the quality of self-tinting lenses by the speed at which the molecules act – and our molecules are fast: ZEISS PhotoFusion lenses darken in just 15 to 30 seconds in bright light or sunshine; inside they clear again completely in 5 to 10 minutes.*