My 550 EX speedlight usually works great with all my Canons--I use a 10D and an Elan 7. But I've been noticing an inconsistency in a lot of my flash pictures at weddings...The problem is this: Canon flash TTL works with the focusing point on the camera. I always have the focusing point set to the middle point because my camera tends to focus on the wrong thing sometimes--like the background behind the people I'm taking a shot of. Therefore, if that focusing point is focused on something dark, I tend to get an overexposure or if it's focused on something light, I get underexposure. Am I making sense? Either I have a blurry shot or my shots are not consistenly lit correctly. Has anyone else experienced this and how do you solve it? For posed shots, it's easy to use flash exposure compensation, but not those really quick shots that are so often at weddings.