Newbie here, never tested lens sharpness although bought two lens already.
I shot some thing printed out on a plain paper posted on the wall, and compared my two lens mounted on a tripod, close distance with an angle at f8, here are the results of 100% crop and no sharpening:
canon 50/f1.8 lens
tamron 18-250/f3.5-6.3 lens
It doesn't fit my idea of tack sharp, and I also don't see a big difference between the two. Did I get a bad copy of canon or good copy of tamron? Or did I do the test wrong?
Also when you purchase a lens, how do you test it on site for sharpness? If it is not sharp, say a bad copy, do you change it at the store or go to the custom service.