Currently there are 9 native Standard Zoom lenses for Sigma SD1 Merrill and all of these lenses are autofocus (AF) type.
Sigma SD1 Merrill doesn't have a sensor based image stabilization system but 6 of these Standard Zoom lenses features optical image stabilization.
Since Sigma SD1 Merrill has environmental sealings (Weather Sealing), you may like to couple your camera with one of these 1 Standard Zoom lenses with Weather Sealings.