I have to get back to correct some things I have got wrong, with respect to the Canon 7D. I did not realise this camera has 18MP, quite an achievement. Yes, as theSuede points out, a full frame equivalent would have around 47MP! And still most good lenses are better at their best apertures.
Kent, I have searched far and wide and no luck with M645 MTF or just about anything else technical on them! It amazes me there is so little apart from brochures on the technical side of our hobby, err, obsession.
Back on the lens res issue for a moment, a guy I greatly respect, Chris Perez, had this to say recently on Lenswork's blog:
"The Canon 7D (the highest pixel density sensor of current DLSRs) resolves 116 line pair per mm.
After putting old prime Nikon and Pentax manual focus, as well as current generation prime Sigma and Canon AF zoom and prime optics to the test, I found all of them out-resolved the sensor. From wide open (in the center of the field, at least).
Think about that for a moment, and then consider how freeing it might be to realize that, by and large, perhaps avoiding the deliberate lowest cost products, currently commercially available lenses are better than the sensor!
Said another way, it takes a really poor optic to under-perform a sensor."
Which is pretty much wat Zeiss say, not in so many words...Sorry for that add-on, last word on it - promise!