I posted a couple of pdf files with good explanations of MTF curves, and how to read the charts. They’re located in blue text on the lens reviews page, and are courtesy of Zeiss.com. The second file is a little more interesting in my opinion. It’s good reading even if you aren’t concerned about that kind of stuff.
Also, thanks to Eric, I have a manual and application chart for the old Minolta close-up lenses, which are still available and cheap on eBay. Go here and scroll to the bottom of the page for the links to both pdf files.
One last item, a few people wrote in and said the comparometer from imaging-resource.com didn’t show the same difference of noise in their A33/ A900 comps as my A33 and A700 comparison page did. That’s because the comparometer is using jpegs, and are not derived from RAW files.