EF-S ultra wide zoom lens with an impressive starting focal length (16mm in 35mm equivalence). Compact design made possible by a new 4 group zoom optical system. A stepping motor (STM) and newly-designed focus mechanism support the Canon EOS Movie Servo AF function to provide smooth and quiet continuous AF during video recording, as well as when shooting photos. A large diameter element and an aspherical lens element help correct aberration to achieve higher image quality One UD lens element helps reduce chromatic aberration throughout the zoom range for excellent image quality with high resolution and contrast. Optical Image Stabilizer for up to four stops of correction.