Imaging Resource has posted sample images and first impressions of the upcoming Canon EOS 5DS R.
When compared to Nikon's D810, the Canon shows more detail at base ISO, which is what it's supposed to do. In the noise category, the EOS 5D Mark III has less of it, but the EOS 5DS R shames it by a fair margin in the detail department. The EOS 5DS and EOS 5DS R aren't for low light hand held shooting, but it looks like they're proving to deliver what they're supposed to as far as detail goes.
We're all waiting to see what the real world dynamic range of this new 50.6mp Canon sensor is going to deliver for us.
There's also comparisons against the Pentax 645Z and Olympus EM-5 II.