The AF 100-300mm f/4.5-5.6 Apo is an easy to carry, easy to handle lightweight and compact 3X telephoto zoom. The AF 100-300 mm f/4.5-5.6 Apo provides superb operation for auto and manual focusing. During autofocusing, photographers can hold the camera in good balance and concentrate on framing, Auto Clutch Mechanism, which does not rotate the focusing ring during AF drive.