12-01-2018, 10:59 PM
A quicker and dirtier approach just occurred to me. How about taking 5 shots of a high contrast subject at infinity (e.g. a house) - one shot where it's at the center of the frame, then 4 more where it's at each of the extreme corners. Finally compare the sharpness of the shots side-by-side on a PC (or a laptop, if one is personally testing a lens he/she considers to buy). Would this work?