This EF300mm f/4L IS USM is characterized by outstanding mobility thanks to the outstanding image stabilizing system. The optics include 2 UD glass elements to thoroughly eliminate secondary spectrum. - Focal length and maximum aperture: 300 mm 1:4 - Lens construction: 15 elements in 11 groups - Diagonal angle of view: 8°15' - Focus adjustment: Rear focusing system with USM - Closest focusing distance: 1.5m / 4.9ft - Filter size: 77mm Compact L-series telephoto lens with an Image Stabilizer which compensates for camera shake with equivalent effect of a shutter speed two stops faster. Two Image Stabilizer modes are provided: Stabilizer Mode 1 (the same mode featured on the EF 75-300mm f/4-5.6 IS USM) and the new Stabilizer Mode 2 which steadies the image during horizontal or vertical panning. The image stabilizer also functions when using the Extender EF1.4xII or Extender EF2xII to provide that elusive 600mm shooting capability.