I have a Nikon D5000 and GX1; I want to learn more about off-camera flash. Strobist recommend the LumoPro LP160. I have a few questions: Am I forced to use this manually, or does it do TTL too? (On the GX1.) Will it work on the GX1's hotshoe? Please forgive the basic questions, but I'm very new to flash photography. I have a Nikon SB400, but of course that uses Nikon's iTTL so won't work with the GX1. And I'd like to be able to use it off camera and use my camera's flash as the trigger. Alternatively to this model, and I better going with something like the Nissin model, designed for 4/3 cameras? I would assume this works fine on the Nikon too.