Here are four test shots with no T/C,1.4X and 2X on aperture priority, spot A/F and spot metering @ 300mm, 420mm and 600mm. All are very good and no post processing. I see no C/A when cropped or extreme zoom but I do have the lens "correction" profiles loaded in the 5D MarkIII. Also the sun was glaring off the sign but all things considered very happy with the lens and T/C's.