The best way to avoid glare in glasses is to simply position your lights and your subject in such a way that they don’t reflect off the surface of the lenses in the glasses they are wearing. In the studio, this is relatively easy to achieve. Out on location, where you have no control over the ambient light and sometimes your subject, we might have to resort to cleaning it up in post.
In this video, Unmesh at PiXimperfect shows us a method we can use to restore detail hidden behind glare and reflections in glasses in Photoshop. He does stress that you do need to have some detail there to begin with that you want to try to bring out.
If the glare is too overpowering and you have absolutely no detail there at all, then this video won’t help you much. You’ll have to try alternate methods at the time of shooting which Unmesh mentions in the video. But if the glare isn’t incredibly strong, and you can still see some detail behind the reflections then this should help you to eliminate it somewhat. You’ll still want to keep some there, just to help with the realism, but you can massively reduce it.
Again, ideally, you want to position your subject relative to the light sources that you don’t get glare in glasses, to begin with, but if you have no choice, then this is a good (if not particularly quick) technique to help you solve the problem.
How do you deal with glare from glasses in environments you can’t control?