I built a water proof bag for my UZi - I hope I am not posting something that has been done to death, but this came up on the thread about adding a gun sight to the UZi, and I thought it may benifit others.
The big Zip Lock bag I used is the obvious part - it is the way that I got it water tight and still take clear shots that is not.
I use a step-up ring for my filters, 49 to 52 mm.
Put the step up ring inside the bag, where you want the bag to thread to the camera.
Carefully thread the filter onto the step up ring, over the bag.
Use an Xacto blade to cut the bag away from the inside of the filter.
You are now pretty much water/dust proof.
The bag still makes things fuzzy through the viewfinder - you could put a mini ring and filter at the back, I think.
I take my camera off-roading - lots of mud, silt, etc get in my open top Samurai. It works - I can even spray off mud from the filter before I wipe it dry. You can even fold the bag in such a way as to be a way to keep rain off the filter in heavy rain.
If you have too large a camera for Zip-Lock bags, use a good quality trash bag, and rubber band it under neath. The key is you can control humidity entirely.
Pics here -
http://www.pbase.com/erikd/waterproof_uzi
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Erik
http://www.pbase.com/erikd
UZ2100, 1.45 Teleconvertor