Okay this is my first TTL flash. I have used manual flashes in the past but that was a long time ago, and I have forgotten most of what I knew. Can someone please explain what the switches are for? I use it on a EOS Elan 7. I for the most part understand the TTL Full and 1/16 (not sure what 1/16 is used for). The one I am unsure of is the switch with the two arrows on it. I tried to order a new manual for it, but got no response from the email I sent. Any help would be greatly appreciated.