I just got a Formatt Hot Mirror ND 1.5 and was surprised at the extreme color cast present. The filter is a 77mm screw-on. I attached a jpg of this, and was wondering if maybe I'm doing something wrong here, the other shots I've seen on the forum using Formatt haven't had nearly the Blue/cyan cast I'm seeing. I'm thinking about giving the Tiffen IRND a go now. Thanks in advance!