Gyro sensors detect unwanted vibrations, triggering the corresponding movement of a correcting lens group perpendicular to the optical axis. This alters the light path, returning the image to its correct position on the sensor or film plane.

The EF70-300mm f/4-5.6 IS USM provides 2-mode IS for shooting immobile subjects. Mode 1 stabilises the image along both the horizontal and vertical axes. For shooting while panning to follow a moving subject, Mode 2 turns off correction in the panned direction and prevents the effect of dragging the subject back through the frame. IS switches off automatically when the camera is mounted on a tripod, thus preventing feedback loops between the IS sensor and stabiliser motor vibrations.

The micro USM motor found in the EF70-300mm f/4-5.6 IS USM employs ultra-sonic frequency vibrations to drive auto focus with unrivalled speed and near-silent operation. Good holding torque stops the lens with precision and accuracy, the instant it arrives at the correct focus point and without overshoot. A high speed CPU and optimised AF algorithm result in a significant increase of AF speed compared to that of its predecessor.

A zoom ring locking mechanism is provided that locks the zoom at the wide-angle setting. This ensures that the lens is carried or stored in its most compact position, preventing possible damage caused by the lens extending and hitting obstacles when being carried mounted on a camera with a strap.