The 12-35mm marks a departure from previous Lumix G lenses in terms of construction. The rear segment of the barrel between the zoom ring and the mount is made of metal, as is the manual focus ring with its finely-milled ridged grip. This immediately gives an impression of build quality that Panasonic lenses have recently lacked. The 12-35mm is also Panasonic's first lens with any kind of environmental sealing, although it's unclear whether this extends beyond the slim rubber seal that encircles the lens mount.
This impression of a quality product is reinforced by the wonderfully-smooth zoom ring action, that rivals Canon and Nikon's top-end lenses for its silkiness of operation. It rotates about 80 degrees between the wide and tele positions, which allows you to fine-tune your compositions with some precision. The electronically-coupled manual focus ring on our-preproduction sample doesn't have quite the same smoothness of rotation, but it does offer extremely accurate manual focusing with a remarkably well-tuned tactile 'feel', which is all that really matters.
The 12-35mm uses the all-electronic Micro Four Thirds mount, meaning it will work on Olympus's PEN and OM-D cameras, as well as on Panasonic Lumix G bodies.
In this view you can just make out the slim rubber seal that surrounds the mount, and helps protect against dust and water getting into the body at this relatively vulnerable point.
The filter thread is 58mm, and does not rotate on autofocusing, which should please filter users.
Next to it is the bayonet mount for the petal-type lens hood (see below).
The zoom ring is 16mm wide, and rotates approximately 80 degrees clockwise from 12mm to 35mm, giving fine compositional control. Its action is beautifully smooth and precise - a cut above Panasonic's existing zooms for Micro Four Thirds.
Olympus users may wish to bear in mind, though, that (as usual) this is the opposite direction of rotation compared to their M.Zuiko Digital zooms.
The finely-ridged manual focus ring is 10mm wide, and unusually is made of metal. Like most Micro Four Thirds lenses manual focusing is 'by wire', and geared such that rapid rotation of the ring changes focus distance quickly, while slow rotation can be used for fine focusing.
Panasonic's implementation works especially well, but it does mean that there's no distance scale on the lens.
Thankfully the 12-35mm has a physical OIS switch (many recent Panasonic lenses have devolved this function to a menu setting on the camera).
For users of Olympus cameras, this allows relatively easy switching between optical and in-body IS systems.
The 12-35mm comes with a bayonet-mount petal-type lens hood, that reverses neatly for storage.