In December 2013, Sony introduced the first modern mirrorless camera with a 35mm format sensor (or full-frame as it is often called). At the time, the only other full-frame mirrorless system was the legendary Leica M which, in addition to being based on a different kind of technology, is purely manual focus.
Nearly five years later, the E-mount system faces much more direct competition. Although Sony recently became number one for full-frame cameras in the US, the two most popular camera brands – Canon and Nikon – have decided to fight back with two brand new mirrorless systems.