Hey, in sports specs for the kiddos, it's really neat to have photochromic lenses and a flash mirror preserves the "cool" look. In fact, some of the demos (from the sports specs frame company that must not be mentioned!) have a clear lens with a flash coat. NEAT-O!
Not only that, but, say in a pair of golfing sunglasses, or motorcycle glasses, or other outdoor sports glasses (like, say, trail running or mountain biking in the trails) it's kind of helpful to have a light-adjustable sunlens. (There are true light-adjustable sunlenses that go from, say 50% absorbtion to 80% absorbtion, but I like to go from 10% to 80% so they can use them in the shade or dusk or night, as well. That means an "Extra active" photochromic. <--shameless plug.)
In those types of glasses designs, it's important to choose a frame that doesn't look el-dorko in the lightened state. That's a tall task. If you use a dedicated plastic sun frame, clear lenses can make it look weird. But if you use a mirror flash coat, even with a lightened lens, it looks totally badness.
But are you messing with the photochromic effectiveness? Aren't you reflecting away some of the activating U.V. light? I would say "yes" (unless the mirror somehow selectively passes the UV through, and I doubt that).
So I ran a dumb experiment. I have some flashcoat on a clear lens sample (material unknown) and I laid it on top of an industry-standard extra-active photochromic lens sample, such that half of the photochromic was covered by the flash coat sample, and half wasn't.
With direct UV exposure, when comparing halves of the lens (one with the flashcoat sample overlaid, one uncovered) by looking through it from the wearer's view or the observer's front side view....
CIRCLE THE CORRECT ANSWER:
a. they were the same darkness on each half
b. the mirror-coated side looked darker
c. the uncovered side looked darker
Reply With Quote
Bookmarks