I have canon 420ex & I have been having problems with my flash producing inconsistent power or won't fire at all in I try to shoot several shots in couple secs, causing little to no flash fill. Same problem even if I use new batteries. My question is how do I solve this issue: It is the battery? Should I switch to NiMH? Or I pretty much have to buy either 430EX II or 580ex to have better recycle time? Last question is 580ex II a better way to go? I shoot a lot of outdoor family portrait & some weddings, also outdoor. Thanks.