jbeale
Well-known member
There are no ND 2.7 that i know.
I guess the filter sizes sold for industrial applications are too small (50 mm) but they come in densities at least up to OD 3.0 (ND 3.0) which is 10 stops down.
http://www.edmundoptics.com/onlinecatalog/displayproduct.cfm?productID=1945
These are cut from larger sheets of glass so I bet they could do a custom size for you if the price was right.
B+W used to make ND 3.0 and ND 4.0 but apparently they ceased production of those types in April 2006. http://www.2filter.com/prices/products/bwnd.html