Tried messing around with a couple different things last night (tissue paper, etc.), and the flash dimmed a great deal. That was using ETTL, so obviously the camera didn't know that there was a diffuser on the flash. How can I compensate for that? Would I have to go totally manual on the flash controls? I don't know my manual controls very well, but I think I had it set at full flash and it still was very dark, even with just a single piece of tissue paper over the flash head.