For a few years, I've owned an Elan7e, 420ex, and a 28-105 f3.5/4.5. I've just purchased a rebel xti which should arrive any day. Woohoo! The 420ex & 28-105 obviously work pretty good together because the flash automatically zooms with the lens. My question is what happens differently (if anything) when I put that flash & lens on my spiffy new xti when it arrives? I realize there is the 1.6 crop factor with the xti. Am I correct in my understanding that this doesn't affect the flash in any way?