1.3 vs 1.5, should not be way off, not more than a couple of stops, which been the case with my older cameras that use mercury batteries. You can try a 625 hearing aid battery to see if it makes a difference. Likely need a hearing aid battery and a rubber washer to hold the zink air in place in the the battery compartment. By the way, hearing batteries will work with the E as well, from the looks of it in the manual a set of 625s with maybe a wadded up hunk of aluminium foil or a small spring to hold the thinner hearing batteries in place. I use hearing batteries in Miranda, Konica, Petri , Kowa and Topecon 100s. Last a couple of months. Hearing Batteries are zink air, so you need to open the battery compartment every time shoot to allow some fresh air in. In my Miranda I drilled a little hole in the cover to let air in.