This telephoto IS (Image Stabilizer) zoom lens is the world's first interchangeable lens for SLR cameras that incorporates an Image Stabilizer. It provides a camera-shake blur correction effect equal to an increase of two steps of shutter speed, greatly expanding the range of handheld photography even with slow speed film and under low light or other difficult conditions. Shutter speed of 1/30sec. is equivalent to 1/125sec. with IS. There are six lens groups in this lens, of which the second is the IS group, moving to prevent image blurring, caused by camera shake. Level of camera shake is detected by vibration detecting gyro sensors. The optical performance features high resolution and high contrast definition that is the true hallmark of EF lenses. With wide focusing ring and zoom ring, its operability is outstanding. A micro USM (Ultrasonic Motor) in the drive system ensures silent AF.