I read or heard a few places including here about how image quality is compromised when the 7D is paired with a consumer-grade (i.e. no "L" glass) lens. I've owned the 7D for a few months now and all I have and can possibly afford are consumer-grade lenses. Can anyone explain how the 7D diminishes the quality of the results under such conditions? And how so? Does it simply exaggerate the imperfections in your glass, or is there more to it? P.S. I'm quite happy with this camera; I'd just like to better understand the potential 'shortcomings.'