FWIW- I still carry a pair of flip-up sunglasses glasses I used to wear on commutes. I got into film photography 15 years ago and old manual film cameras and became obsessed with estimating light conditions and exposures in my head, so I stopped wearing sunglasses. My step-daughter bought a fancy light meter for her photography class and I was able to match its readings. A lot of simpler, older cameras also have lenses that focus, but no way to focus them (not through the lens nor with a built-in range finder) so you learn to estimate distance in your head, or using your two eyes and fingers as a range-finder. Sorry, geeked out there for a second.