The sony 500mm f4 g ssm lens is a high performance ultra telephoto lens with a 500mm fixed focal length and is ideal for capturing sports wildlife and other demanding imaging applications requiring a high level of magnification the bright f40 aperture allows use of faster shutter speeds to broaden shooting opportunities and is great in low light the g stands for sonys gold series of lenses and are sonys top shelf professional lenses offering excellent image and build quality the sony 50