These zoom lenses feature a built-in motor to position the lens elements while zooming. The zoom ring is used for zooming, focal length change, and focusing. Slightly turning the zoom ring to the right or left starts zooming at one of three speeds. Turning the ring further engages faster speeds. Pulling the ring back towards the camera enables motorised manual focusing. Interesting features offered with these lenses on Dynax Series-xi cameras included: Auto Standby Zoom, Auto Compact, Image Size Lock and zoom tracking with the Child and Sports Action 2 Creative Expansion Cards when used with certain Dynax Series-xi and Series-si cameras. Minolta Dynax xi and MZ zoom lenses. Minolta produced a special class of zoom lenses for the Dynax series-xi cameras. These zoom lenses incorporated motors to provide focal length change or zooming. By using a motor for zooming, the designers could add special features to the xi cameras and Creative Expansion Cards that enable the lens focal length to be automatically set for a particular affect as determined by the camera's programming. Special zooming features included:*Auto Standby Zoom (ASZ) available in the Dynax 3xi, 5xi, and 7xi camera bodies. *Image Size Lock available in the Dynax 5xi and 7xi cameras. *Automatic compact at camera switch OFF in all Dynax series xi and si cameras. *Program Zoom Control with Child Card and Sports Action 2 CE cards with Dynax 7xi, 9xi, and 700si.*Focal length viewfinder information with 9xi and 700si.Dynax series-si cameras will support the normal functions of these xi-zoom lenses but do not offer specialized, focal length setting functions. Many of the xi lenses are also available in MZ or "Manual Zoom" configurations. These lenses include:28-80mm f/4-5.628-105mm f/3.5-4.5100-300mm f/4.5-5.680-200mm f/4.5-5.6