Leica shows just how small a lens can be, if you have a camera with a half-sized sensor and no big mirror-flipping gap between it and the lens itself. This is the new LUMIX G 20mm ƒ1.7 ASPH, and it aptly belongs to the class of lenses called “pancake”.
That 20mm focal length translates to a 40mm equivalent, a little longer than the standard rangefinder length of 35mm. But its the speed that we’re interested in, that this lens is fast. ƒ1.7 means enough light will be gathered for low-light hand-held shooting, and that, when opened right up, it will throw pretty much everything out of focus except, say, your subject’s eyes. The ASPH part means that the lens uses aspherical elements, which are, as the name suggests, not a section of a sphere. This keeps lenses simpler and sharper.