Here is a 100% crop of the 50D vs a matching enlargement crop photo of the 5Diii. Both are using the Tamron 150-600 @ 600mm f8 iso 200 .3 sec. on tripod. Distance is 10 meters. Guess which one is from the 50D. This is the dead center of the lens.
To be clear, both shots from the same position and you cropped the 5D3 image 1.6 times more? So it's a 160% crop from the 5d3?