I have a really nice "norka" barn door shutter in my possession. A student of mine has decided to build him self a big camera, so he "just" copied the shutter, but made it MUCH bigger.. I am quite impressed! it works fine. The fun part was to hear where he got the bits and pieces for it.. (his father is a doctor, so some stuff comes from a doctors office - some come from the inside of an old broken DVD player... and so on. I'll show you a couple of images here. First the original Norka - then Christian's. (maybe there could be a market for this? I hear all the time, that people wants a BIG shutter for their BIG lenses, and this will accept very big ones.!) Anyway, I was surprised how "easily" he made this lens. But it needs a large lens board. (I'll check the exact mesurements tomorrow and provide them..