Remember those colorful '90s bookmarks (and rulers, binders, postcards) printed with weird plastic lines on them so that if you turned them one way or the other, a different picture would appear, or the picture would move back and forth? Like thisHarry Potter one. That technology is called "lenticular printing," and I've only ever seen it as a gimmick for for kids' books or Cracker Jack prizes.
Well, Spanish organization ANAR, which works with abused children, just figured out a way to use it in their street ads to solve a major messaging problem. It's a problem that faces many groups that work with systematically abused populations (battered women, enslaved immigrants, sex workers): How do we get our information delivered just to the eyes of someone who needs to see it when they may be walking down the street with their abuser? ANAR wanted a way for kids to see an ad with a phone number they can call for help, and an adult to just see a generic anti-child-abuse PSA.
I'm not sure how publicizing it on the web really serves the ads' secretive purpose, but I guess it wasn't going to stay completely secret for long. It's just a lesson in creative messaging for the public good. (And it makes me look at shiny rainbow Lisa Frank binders in a whole new way.)