I was probably using a 1a skylight filter as that is on the lens most of the time. The only other filter I own is a polarizer. The WB was set to auto (-1), and it was a 30 second/f8 exposure at dusk. I shot many pics that night ('Empty', also on usefilm), and many had the same blue cast. I think the blue is from the brighter blue sky to the left, outside the shot. Cheers,