"I can't say enough nice about the Nano light. It was really impressive. It doesn't kill batteries and provides plenty of light for a night dive on its own. The arms worked great and the 3 way clamp to put the Nano over the center of the lens axis worked really well. As I said, it also served as my primary light on the 5 night dives. I did 27 dives, close to an hour per dive, and changed out the batteries twice. I probably only needed to do it once. I was just making sure it didn't run out. Focus was definitely not as fast as an SLR but I didn't take near as many pictures of fish's tails as I did with my Oly 5060."