I recently purchased the B&W ND110 37mm 10 stop ND filter to use on my LX7 with the filter adapter. I took it out to a small cascade on Sawmill Creek, not far from my home, to give it a try. Unfortunately, I went at the worst possible time of day and the sun happened to make an appearance so I was shooting directly into the glare of the sun on the water. I added a polarizer as well so along with the built-in ND filter I had about 14 stops of light reduction going on.
A 10 stop filter is really dark so there’s no way for the LX7 to focus while it’s on. You need to switch to manual focus, remove the filter, set your focus point, then reinstall the filter. Some of my exposures were in the 120 second range and that coupled with the same amount of time spent on the “please wait” phase after the exposure means that you’ll spend a lot of time just sitting there. Make sure you go to the bathroom before heading out to sit beside all that running water :-).
You need to zoom in a bit to avoid vignetting with both the polarizer and the ND filter installed as both are about the same thickness and will show up at maximum wide angle. Either one by itself isn’t a problem though.
I was shooting in manual mode, rotating the exposure wheel until the display indicated a 0 EV exposure but I often found that this wasn’t enough. Most of the shots that came out were ones where I dialled in about 1 to 2 stops of indicated over-exposure however this may have been due to the bright glare from the sun. In this shot the sun is directly in front of me and I had to shield the lens to prevent any flares. Taking multiple shots at different exposures is a good idea.