If you are interested in the MTF of a lense at really high spatial frequencies, you might want to use a test-chart of e.g. a slowly swept sinoid, meaning that you know what (single) frequency is fed into the system at a particular spot. If you then use something like the D800E (or the D7100) without a AA-filter, you know that the camera sensor has a wider frequency response (even to aliasing frequencies).
I'm mainly interested in the MTF results of lenses for purchasing decisions. Those Photodo MTF results were a great buying guide. If I already own and use the lenses, I know their strengths and weaknesses.
My main concern when I buy a new lens is that I can expect it to be better than what I already have, at least in some respects.
For example, ever since buying a Nikon D7000 about 18 months ago I've been searching for a telephoto zoom with Nikon mount and VR (OS or VC) that at least matches the performance of my Canon 100-400. The three main contenders were the old Nikkor 80-400 VR, the Sigma 150-500 OS and the latest version of the Sigma 55-500 which now has OS.
I find it somewhat ridiculous that in this modern age of sophisticated technological development I can't find any reliable MTF results that compare all four lenses, including the Canon 100-400 which is my benchmark.
I can eliminate the old Nikkor 80-400 because there's so much anecdotal evidence that the Canon is the better lens. Both lenses have been around for a long time.
I can eliminate the Sigma 150-500 OS, but with less confidence because there are no comparisons at either Photozone or DXO. That leaves the Sigma 55-500 OS which, anecdotally, seems to be more highly regarded than the 150-500 and is also more expensive than the 150-500, which tends to imply it should be sharper.
Of course, now that Nikon has upgraded its 80-400, that would seem to be the logical choice for me. However, the Sigma 55-500 is about $1,000 cheaper and has a more useful range of focal lengths. I'd really like to know, for example, whether the new Nikkor at 400mm can produce the same or better detail than the Sigma at 500mm. If it can, and is also sharper than the Sigma at other focal lengths down to 80mm, then the matter is settled. I'd be prepared to pay the extra $1,000 and save a few hundred grams in weight, which is also a consideration for me.