Hey guys. I got a decision to make. I plan on starting to work as a portrait photographer next year, and I want to upgrade my Rebel XS(both for IQ and having a backup body purposes). I've narrowed it down to a 40D/50D or a 5D Mk I; as they are all within my budget I want to know how substantially the 5D's FF sensor affects image quality compared to the 40/50D. Regarding the 5D's AF I am aware of how bad it is, but I figure I don't really need a killer AF considering I plan to do portraiture where a fast AF isn't paramount(though it should be accurate of course). And I use center focus point 99% of the time. As to the lack of Live View and sensor cleaning, these things don't really bother me. Another thing is the size of the viewfinder, is it a substantial leap from the crop cameras? I appreciate any help/advice.