Originally Posted by ltdstar 
the two photos that you took are different, one is 1/50sec and the other is 1/90sec...if you want to test a lens you should shoot it in manual and have same setting on both lens...
...and put it on a tripod and focus manually. The last point is absolutely mandatory unless you want to test the AF system and not the lens. If there are some sharpness problems, try focus bracketing...