Looking for some help with a setup I want to achieve. I am using a7D and 580EX II which I've been using off camera by triggering it optically through the popup camera flash. I have been looking at a Yongnuo YN-560 II and see it has the ability to be set to a slave and triggered optically. So can I use the 58OEX and Yongnuo YN-560 II off camera on a stand so that they both trigger optically via the popup flash? At this stage I don't want to get radio remotes so am happy with this setup if it works. I only shoot flash manually so don't mind if the Youngnuo doesn't have ETTL options. Is there any justification in spending more and getting a 480ex, or will this third party flash do what I want?