Telephoto zoom lens that builds on the legacy of the popular EF300mm f/2.8 lens. Fast f/2.8 maximum aperture throughout the whole zoom range for great control over depth of field, bokeh, and low-light shooting with fast and reliable autofocus. Excellent image quality: highlights include one flourite lens, and 4 UD (Ultra-low Dispersion) glass elements, flourine coating, and Canon SSC (Super Spectra Coating) to minimize ghosting and flare. Built-in function/focus preset selector switch allows you to program a focus preset recall into the buttons at the front of the lens. Optical image stabilization — up to 5.5 stops* of shake correction. Up to 6.0 stops Coordinated IS when paired with EOS R series cameras featuring In-Body Image Stabilizer (IBIS)