The Canon RF 100-300mm f/2.8 L IS USM is a well-rounded lens for indoor sports, events, and theater, fashion, and other subjects benefitted by the unique mixture of long reach, high speed, adept image stabilization, and fast autofocus. The 100-300mm zoom design offers more versatility for tracking moving subjects, recording candid moments from a distance, and backing off from scenes a bit for a wider frame for more context. A wholly new optical design includes fluorite elements and ultra-low dispersion glass, plus one aspherical element, to achieve a higher degree of clarity and sharpness with virtually no distortion. The dual Nano USM system uses both a ring-type USM and an STM mechanism to realize quick and accurate focusing. The smooth and nearly silent focusing suits both photography and video applications and there is full-time manual focus control available. The focus range limiter can be set to the full focusing range, from 5.9' to infinity, or from a 19.7' to infinity range for quicker performance if working exclusively with distant subjects. Weather-sealed design enables working in harsh environments and prevents dust and moisture from reaching the interior of the lens. Also, there is a front fluorine coating that prevents water, oils, and other residue types from sticking to the lens, making it easier to clean. Internal focusing and zooming design maintains the overall length of the lens during operations and promotes quicker operations and more robust weather sealing. control, there is a Focus Preset button near the rear of the lens, which can be triggered with your right hand during use. This function allows pre-focusing on a spot, storing this focus distance, and being able to instantly return to the memorized position at the push of this button. Alternatively, a side switch enables utilizing these buttons as a secondary Lens Function (L-Fn) button instead. Programmable Control Ring can be used for lens-based adjustment of various exposure or camera settings and comes with a click-stop operation by default for tactile feedback.