Enables silent and high-speed focusing

USM (Ultrasonic Motor) was first put into practical application in the world by Canon. USM drives the lens by transforming ultrasonic vibrations into rotation energy. Not only does it consume little power, it has high efficiency, torque and response, enabling high-speed focusing with almost no operating sound emitted.

There are three types of USM . The round-shaped Ring USM is simple in structure, and is best suited for use in a circular lens tube. It is especially useful for driving lenses such as large-diameter or super telephoto ones due to its high torque, and it also allows for full-time manual focusing. Meanwhile, the Micro USM can be employed on many types of lenses because it is low in cost and not subject to restrictions on the lens diameter. In 2002, Canon contributed further to the downsizing of lenses with the development of the Micro USM II, which is about half the size and weight of the Micro USM . And in 2016, Canon introduced Nano USM, which not only realizes a high speed AF that rivals that achieved by Ring USM, but also is able to operate quietly and seamlessly. It’s not an exaggeration to describe Nano USM as the most ideal motor for normal-use lenses that are meant to handle both still photography and movie shooting.

Ring USM

Micro USM (Left), Micro USM II (Right)

Nano USM—The thin and tiny USM motor that achieves fast and smooth AF

Thin and compact, this USM, the latest to be developed by Canon, made its debut in 2016 on the EF-S18-135mm f/3.5-5.6mm IS USM. Computer chip-shaped (a factor that allows a more compact lens design) with power sources in the form of transducers, it connects directly to the AF actuating mechanism. It possesses a speediness and responsiveness that rivals that of the Ring USM, combined with a control that equals that of STM (lead screw-type). Its main benefit lies in enabling quiet, smooth AF operation in compactly-sized lenses such as standard zoom lenses. Also very suitable for movie-shooting, its high speed AF is able to handle scenes with subjects that are moving at a fast speed as well as those with unpredictable movements.

The Nano USM is shaped like a computer chip, and has 2 transducers in its centre.

A cross section of the EF-S18-135mm f/3.5-5.6 IS USM, released in 2016 and the first lens to carry the Nano USM. Moving along the top of the slider, the Nano USM directly drives the main AF power source. As this motor not only allows for fast and smooth AF but is also small in size, it makes it possible for the lens that utilize it to be around the same size as lenses with STM.

Enables MF immediately after AF

Many of Canon’s EF lenses are equipped with “full-time manual focusing”, which allows manual focus right after auto focus is complete, just by turning the focusing ring and without the need to switch to MF mode. All Ring USM and STM lenses support full-time manual focusing.

Super Spectra coatings ensure accurate colour balance and enhance contrast. They also reduce flare and ghosting – a common problem caused by light bouncing off a camera’s sensor

The short telephoto focal length of the lens slightly compresses perspective, reducing the size of prominent facial features for a flattering result.