Because almost all of my shots have been outdoors, I have not been using a flash on my Rebel TI. I am beginning to look into external flashes, and when I checked the sync speed for my camera, I was disappointed to see 1/90 of a second. Is there any way around this? I read somewhere that the 550ex can override this, but am not sure how that works, and would prefer to get the 420ex if it is capable of doing the same thing. Any help would be greatly appreciated- thanks!