Panasonic 10-25mm F1.7 ASPH is an Auto Focus (AF) Wideangle Zoom lens with FourThirds max sensor coverage. When mounted on a FourThirds sensor camera, it will give you an FF equivalent focal range of 20 - 50mm. Providing a max aperture of f1.7 at 10mm, this lens is remarkably fast on wide end. Even better, having an aperture of f1.7 on tele end, this lens is exceptionally fast through out its range.
Panasonic 10-25mm F1.7 ASPH is weather sealed which makes it an ideal lens for outdoor use, especially when coupled with a weather sealed camera body.