Thanks for your replies.
Im from the old school and used 6x7, 5x4 and 10x8 when I used digital for the first time I just thought it was crap, colour fringing round everything being as I use wide lens almost all the time (I dont do pro commercial work any more) Ok its mostly due to the kit lens.
I guess what I really want to know is, is the 400D better interms of fringing with a prime wide lens? I spent ages with post processing in DXO Optics pro
and photoshop to sort out the fringing with the 300D. I want a situation where that is reduced as much as possible.