I was playing around last week with options for using regular commercial photography filters. After measuring with my digital micrometer my best guess was the threads are 30mm on the P3 camera so I ordered a step down ring kit (30-37mm) and some cheap 37mm filters to test for fit and performance. I don't want the weight of size of 37mm, but need the extra distance to clear the front of the lens and be able to reach the threads. First attempt found the 30mm ring will go on a couple of turns and locks up hard, so that's a fail and I've gone back and ordered a 30.5mm ring. I really was not happy with the additional weight of just the ring, so really not an optimal solution. What we really, really need is just an aluminium 30.5 extension tube, internal threads, about 7mm in length, which would then allow us to use any standard 30.5mm lens filter quickly and easily. If anyone has a recommendation, I will order, test, and share results. I have ordered some 30.5mm filters to see if I can Macgyver together something that works.