Effect similar to fluorite lens elements

The chromatic aberration correction effect is remarkable when a fluorite element is used. However, due to the high cost of fluorite compared to other materials, it cannot be employed widely on many lenses. To resolve this issue, Canon developed the UD (Ultra Low Dispersion) lens element, which is characterized by a low refractive index and low dispersive properties. It is widely employed in many lenses due to its ability to enhance the elimination of secondary spectrum.

Corrects angular and shift shakes

In general photography, angular shake, which occurs when the camera is tilted, may have a large impact on the resulting image. Meanwhile, in close-up photography such as macro shots, the image is subject to shift shake, which arises from displacement of the camera parallel to the plane in focus. The Hybrid IS is equipped with an angular velocity sensor (vibration-detecting gyro sensor) that detects the angle of the camera shake with respect to the optical axis, as well as an acceleration sensor that detects shake in the direction perpendicular to the optical axis. In addition to angular shake, shift shake is also corrected to further enhance the image stabilisation effect. In this respect, Hybrid IS effectively corrects camera shake and and unintentional image blur during handheld shooting, allowing sharper close up shots of flowers, insects and other common macrophotography subjects.

Angular shake

Shift shake

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

MicroUSM (Left) MicroUSM 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 center.

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 high-speed and precise AF

The inner focusing and rear focusing systems adjust the focus by moving only some of the lens elements inside the lens. Inner focusing refers to the type where the focusing lens group is located in front of the aperture diaphragm, while this group is positioned behind the aperture diaphragm in the case of the rear focusing type. As a smaller number of lens elements need to be moved, AF speed can be increased, and the size and weight of the entire lens can also be reduced. Besides, the front of the lens does not extend out during focusing, thus making it easy to achieve an integral lens structure, which in turn contributes to the enhanced robustness of the design. Yet another advantage of this system is that it enhances the operability of polarising filters as the filter mount does not rotate during focusing.

EF24-70mm f/2.8L USM Rear System                                  EF400mm f/5.6L USM Rear System

EF70-200mm f/2.8L IS II USM Inner System

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.

Dust- and drip-proof for shooting under harsh conditions

Many of Canon’s L lenses come with a dust- and drip-proof structure, with rubber sealing applied to the interface area between the joint of the mount and the camera, as well as sealing at the movable parts such as the focusing ring and the lens extension tube. Rubber materials are also employed even at the smallest parts, such as the switch panel and the insertion slot of the drop-in filter compartments. The excellent dust- and drip-resistance enhances the usability of lenses under adverse weather, and helps to address the needs of professional photographers who are required to perform shoots under harsh shooting conditions. Fluorine-coated lenses allow dirt attached to the lens to be wiped off easily.

Expresses point light sources in beautiful round bokeh

The aperture is made up of several blades, the number of which determines the shape of the bokeh effect, such as in the case of illumination, light seeping through the leaves of a tree, and light reflection from the water surface. Light normally appears round when seen through our eyes, thus expressing light in a circular shape adds a more natural and soft touch to the resulting image. Almost all EF lenses employ a circular aperture diaphragm.