Image Resource updated their Comparometer to include the Fujifilm GFX 50S so I took the time to put together the comparison above to see how these 4 similar megapixel cameras compare at 100 ISO and 12,800 ISO for Fujiaddict. At base ISO they are all very similar, but by 12,800 ISO the Sony a7RII pulls ahead. If you check out Image Resources Comparometer the Fujifilm GFX50S is the best by a hair at base ISO arguably followed by the Sony a7R and then the Pentax 645Z. The Canon 5DS R isn’t far behind, but it really depends on what part of the image you examine. Each camera has it’s own strength. You can do your own comparisons here.
Sony a7rII B&H Photo / Amazon / Adorama
Fujifilm GFX 50S B&H Photo / Amazon / Adorama
Canon 5DS R B&H Photo / Amazon / Adorama
Pentax 645Z B&H Photo / Amazon / Adorama