The G3 includes full HD video recording capability in AVCHD format in accordance with the MFT system design standard.

Physically, the G3 approximates the size of the small Panasonic Lumix DMC-GF2, but includes an electronic viewfinder (EVF) and an articulated, touch control-enabled LCD panel.

[3][4] At the center top of the G3 there are weak built-in pop up flash with GN10.5 at ISO160 (GN8.3 at ISO100), hot shoe and stereo microphone (G2 still monoaural).

In the United States, the suggested MSRP for the camera and 14-42mm kit lens was US$700.00 and GBP628.99 in the United Kingdom[6] The Micro Four Thirds (MFT) system design standard was jointly announced in 2008[7] by Olympus and Panasonic, as a further evolution of the similarly named predecessor Four Thirds System[8] pioneered by Olympus.

[9] The equivalent Canon APS-C DSLR EF-S 18-55mm f3.5-5.6 kit lens weighs 190g, and is 69mm in diameter and 80mm in length[10] In 35mm camera format the Micro Four Thirds system sensor has a 2× magnification factor on its lenses whereas the APS-C sized sensor cameras have 1.6× magnification factor.

While the older Four Thirds system design standard allowed the incorporation of a single lens reflex (SLR) camera design including a mirror box and pentaprism based optical viewfinder system, the MFT system design standard sought to pursue a technically different camera, and specifically slimmed down the key physical specifications which eliminated the ability to include the traditional complex optical path and the bulky mirror box needed for a SLR optical viewfinder.

Instead, MFT uses either a built-in (Panasonic) or optional (Olympus/Panasonic) compact electronic viewfinder (EVF) and/or LCD back panel displaying a Live view from the main image sensor.

The MFT system design flange focal length distance allows for, through use of an adapter, the possibility to mount virtually any manufacturer's existing and legacy still camera interchangeable lens (as well as some video and cine lenses) to an MFT body, albeit using manual focus and manual aperture control.