The EF 300mm f/4L IS USM Lens from Canon is a telephoto prime lens with two-mode optical image stabilization which compensates for camera shake up the equivalent of two shutter speed stops. Stabilizer Mode 1 corrects vibrations in all directions and is mainly effective for shooting still subjects and Stabilizer Mode 2 steadies the image when panning vertically or horizontally.
An ultrasonic autofocus motor (USM) enables fast, smooth and silent autofocus and fulltime manual override allows for precise manual focus even in autofocus mode. Two ultra-low dispersion (UD) glass elements reduce aberrations and provide clear images and accurate color. The minimum focus distance for this lens is 4.9'.
The lens features a built-in lens hood and a removable, rotatable tripod collar for stable and secure tripod mounting, the lens is compatible with Canon 1.4x and 2.0x extenders.
Additional info .