I have Shade 3 and Shade 5 for my stormtrooper. Shade 5 are for outdoor events, shade 3 indoor. If you have shade 5 indoor, you can't see a thing in front of you.
I did an indoor event yesterday with my shade #5... it looked ok to me... once my eyes were adjusted it was fine... I have thought about getting a shade #3 along with my #5 and just taking the chicago screws out and switching them for different events.
I believe the movie accurate one is smoked acrylic, but for helmet making purposes, the welding shields work better... I think both are considered canon though.