Here's a shot from a recent family reunion shoot I did. It was lots of fun and the pictures turned out well, but I had a challenge I've been having a lot lately - a subject (the girl on the left hand side of the bench) wearing photochromic (or self-tinting) eye glasses. These are quite popular these days, as they give the wearer visual comfort when the sun is bright, and eliminate the need for separate sunglasses.
Not invented by a photographer, I'd wager, these glasses present a challenge when shooting in any amount of light. Most times, the easiest solution is for the subject to take them off, but if that isn't feasible one can hide them in the dark until just before the photo is taken and try to get some shots before they tint up again. According to Wikipedia, the lenses darken in less than one minute and begin to clear in darkness in 5 about minutes. You can see how this is challenging in a photo shoot. I'm a bit curious to know the future of this technology. This too shall pass? (Fingers crossed.)