If you're still not sure, do a test:
1) Get a carboard box, or a rucksack, or a container you can place an object in.
2) Place any object into the bag/box and leave a gap/opening so you can clearly see the object.
3) Fill the visible gap/opening with the visor, and insure that there is pretty much no light inside the container.
4) Can you still see the object through the visor? If not, then the visor should work fine.
If so, then there's 1 of 2 possiblities,
(A) There was still entering the container.
(B) Your visors tint is not strong enough to hide your face.
Like people have said though, if you got the wrong visor, you can purchase some window tint that should do the trick. I wouldn't try using Data's idea, glass paint, but if you're up for that you could certainly try, but I'd research it a little first.
-S420