Much like transition lenses on glasses, the SolFX face shield from Transition Optics adjusts the tint of the shield according to the light present, making it perfect for both day and night riding, as well as the more dangerous time to be out on your bike - sunset and twilight. The SolFX shield uses photo-chromatic coating which remains clear at night, and darkens to a medium smoke tint during the day.
If you’re looking for something that doesn’t make morning and evening riding difficult, this could be an option. It’s especially good for winter riding, although on a cloudy day the glare can make the shield darken when you’d prefer it to be clear. The SolFX is compatible with many of the major helmet manufacturers including Arai, Shoei, Shark, Nolan and Suomy. At this stage it looks like the SolFX is only available in North America, but for more details, see the Shield transitions site.
Source | Motorcyclistonline.com