images taken in take light, from same spot, same AF point, same lens.
Canon EF 50mm @ f/2, 1/1000s cropped 1:1 images:

T2i @ 1600ISO

5D @ 1600ISO

T2i @ 6400ISO

T2i @ 12800ISO (H)

5D @ 1600 ISO with +3.5 exposure in LR, minor white balance adjustment