It just needs to be said that I think there is some confusion between a crop factor and a focal length multiplier. Using a 70-200 lens on a 40D yields the exact same amount of "zoom" as it does on a 5D. You aren't actually any closer with a 40D. All you're doing with a 40D is cropping down your image to get a sense that you're closer.
Think of it in terms of digital zoom. The optical zoom on your lens doesn't actually change at all. It's just that on the 40D, it's cropping down on the image and making it *appear* as if you were closer to the subject.
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