Shumway, I have used photo chromatic sunglasses, but being of a certain age I find reading small print in low light difficult. Sunglasses are great for looking outside, but not for digital instruments. So now I have normal bi-focals and for looking out I merely pull my helmet visor down. The other problem with photo chromatic glasses is that they are slow to react, especially from dark to bright. That can cause problems when the sun goes in and you are still wearing dark glasses.