The contax G2 is an extraordinary new kind of camera system, an electronic rangefinder. This revolutionary design enables the manufacturer to combine the light weight of a Leica rangefinder, with the speed and accuracy of electronic autofocus, with the superior optics of Zeiss lenses.
With a rangefinder camera, one does not look through the "taking" lens, but rather through a viewfinder that aproximates the view. Because there is a direct path from the taking lens to the film plane, there is no need for a mirror, and this provides the camera designer with two benefits.
First, the size, weight and noise of the mirror box can be dispensed with. More importantly, however, is the freedom it affords to the lens designer. A lens designer must use all sorts of tricks to make wide-angle lenses work with an slr camera, because the mirror must be able to clear the rear element of the lens as it flips up. Without the need for this extra clearance, the lens designer may let the rear element be as close to the film plane as he chooses. This has allowed Contax to use the super-sharp Zeiss Biogon and Hologon lenses as the G2's wide angles.
The electronic rangefinder refers to the focusing mechanism of the camera, one that uses triangulation to determine the distance of the subject from the camera. In the G2, this is both extremely fast and accurate.
Wide angles are the preferred lenses for use with any rangefinder camera for several reasons. First, there is no depth of field preview on a rangefinder, since everything apperas to be in focus. Second, the parallax effect (the viewfinder does not exactly correspond with the field of view in the taking lens) is more pronounced with longer lenses. Typically, I use the 21mm and 28mm lenses with the G2, although I also have a 45mm and 90mm.