Difference: 3.6 mm² (0.4%) 5D Mark III sensor is slightly bigger than D4s sensor (only 0.4% difference). Note: You are comparing cameras of different generations. There is a 2 year gap between Nikon D4s (2014) and Canon 5D Mark III (2012). All things being equal, newer sensor generations generally outperform the older. Pixel pitch.
EOS 5D Mark IV DSLR Camera Bundle with EF 50mm f1.8 STM Lens + EF 75-300mm f4-5.6 III Lens + 256Gb Memory, Accessories, Black, full-size (1483C002) 4.3 out of 5 stars 6 Canon EOS 5D Mark III 22.3 MP Full Frame CMOS Digital SLR Camera with EF 24-105mm f/4 L is USM Lens (Certified Refurbished) The camera has been improved over its predecessor in most areas and comes with a 22MP full-frame EOS-1D Mark III: AC Adapter Kit ACK-E4 (bundled accessory) EOS-1D Mark II N: DC Coupler Kit DCK-E1 (bundled accessory) EOS-1D Mark II: DC Coupler Kit DCK-E1 (bundled accessory) EOS-1D: DC Coupler Kit DCK-E1 (bundled accessory) EOS 5D Mark III: AC Adapter Kit ACK-E6 (sold separately) EOS 5D Mark II: AC Adapter Kit ACK-E6 (sold separately) EOS 5D Compare Fujifilm X-Pro2 (24.3MP) vs. Canon EOS 5D Mark III (22.3MP) on sensor size (28.29mm vs. 43.27mm diagonal), pixel pitch, pixel density and other specs.Unfortunately, Canon decided to use its ancient 11-point autofocus system from the 5D Mark II, which only has one cross-point sensor in the center, as shown below: This 11-point AF system is not as versatile as the AF system on the 5D Mark III and at the same time is also inferior to the 39-point autofocus system found on the Nikon D600 / D610Lw78a.