Sign guys use that stuff. They print on it and stick it on city busses with adverts etc. The passengers can see out quite will, although at reduced light levels. And you're right, it is very difficult to see through, although whilst picking nits, I would have to say that technically, the tiny holes are the same dimension regardless....as I drift off in b o r e d o m.....
The only real visual 'diode', is a webcam.. or any other kind of cam, but not a cam'el', because when you lift up a camel's tail, and peek inside, you don't get to see what the camel sees. Or so I'm told.....told you I was bored...