Get Breakthrough Photography X3 filter at B&H Photo (available soon).
Breakthrough Photography introduced a line of high-grade filters in 2015, dubbed the “X3” line. See the in-depth description of the technology used to manufacture these filters.
When contacted by Breakthrough Photography, I elected to try the 10 stop neutral density filter, because other brands have disappointed with severe color and tint shifts: could the X3 deliver what other filters had failed to do?
A 10-stop ND filter is very dark. With some stopping down, much longer exposures can be made than would otherwise be possible. Purposes include water blur in sunlight, very bright subjects, or photographing subjects that would otherwise be obscured by transient objects (cars, people, etc). By greatly increasing exposure time, these objects can be made to disappear.
In the field, it can be useful to have carry densities of 3, 6 and 10 stops which covers most shooting situations. Using a step-up ring allows using a larger filter size on lenses with a smaller filter size (so that one does not have to carry sets of ND filters in too many sizes).