Seizing the opportunity to try out the Sony A1 camera with the Sony 100-400 GM lens, I visited Woburn Safari Park. This is a perfect lens for zoos and wildlife, although it is relatively heavy when carried around all day. It is, however, significantly lighter than the longer 200-600mm lens. With the 100-400mm lens, autofocus was absolutely superb. Bird-AF and Animal-AF worked surprisingly well.