First Looks at Sigma 500mm f/4 DG OS HSM Sports Lens Image Quality

Image quality, vignetting and distortion test results from the Canon EOS 5Ds R have been added to the Sigma 500mm f/4 DG OS HSM Sports Lens page.

Definitely follow (minimally) that first link. I think you will like what you see.

We do not yet have the Canon EF 500mm f/4L IS II Lens tested on the 5Ds R but will have the Sigma results from the 1Ds III soon to make this direct comparison possible. However, the Canon 500mm f/4L IS II and the Canon 600mm f/4L IS II perform similarly and the Sigma 500mm f4 Sports vs. Canon EF 600mm f/4L IS II Lens comparison is available now.

B&H has the Sigma 500mm f/4 DG OS HSM Sports Lens in stock (Nikon F mount is on backorder).