Panasonic 45-200mm f/4.0-5.6 Lumix G Vario MEGA OIS Zoom Micro Four Thirds Lens for Panasonic and Olympus Micro Four Thirds Cameras

Lumix G VARIO 45-200mm/4.0-5.6 zoom lens w/MEGA Optical Image Stabilization covers the 35mm equivalent from 90-400mm to help the user capture crisp, blur-free, shots when shooting sports events, wildlife and other distant subjects
Customer Review: Nice lens for the price
The lens is first and foremost, small. So if you bought the G1 for the quality of its image vs the size then you will be pleased with the extended capability this lens brings to the G1. If size was never an issue then this lens will disappoint somewhere along the line as there are better sharper (bulkier) lens out there. I am very happy with this purchase but it is by no means my primary lens, which unfortunately will remain the kit 110mm for the foreseeable future. Love the size and quality and I am sure if the G1 suited your requirements then this lens will too.
Customer Review: Panasonic 45-200 Lens for G1 Camera
This lens has problems auto-focusing at maximum zoom in low light, such as trees in open shade in midday. I've eliminated all operator variables that can adversely affect auto-focus, and am left with this lens' problems. By comparison, the thousands of photos I've taken with a Panasonic FZ-50 point-n-shoot camera, with 420 mm effective zoom, have about the same success rate as this camera-lens combination, so even though the G1 has a "very fast" auto-focus with this lens, that doesn't apply in lower light, and it may not focus at all.