The E-M1 basically inherits all the features of the recent Olympus mirrorless cameras such as built-in WiFi, five-axis image stabilisation (but an improved version), and even weather sealing, while adding a few of its own.
On the design front, the E-M1 continues the retro design that brings to mind the classic OM series of classic Olympus SLRs and this time, the camera is much closer in size to a classic OM camera.
