The new Nano USM that made its debut on the EF-S18-135mm f/3.5-5.6 IS USM (reviewed here ), the kit lens of the EOS 80D, is a cutting-edge actuator that overturns the conventional wisdom on AF motors. Boasting a miniature size that is smaller than the fingertip and a high-speed response, it is packed with technologies that have garnered wide attention. In this article, let us learn more about the characteristics of Nano USM, which has a compact and simple structure, and see how it may revolutionise our shooting environment. (Reported by: Ryosuke Takahashi)
Special features of Nano USM
Feature 1: One of the three unique types of USM
As with other types of USM (Ultrasonic Motor), Nano USM is installed on the lens in the area indicated above by the red frame. The compactness of the motor adds a high degree of versatility to the lens design, while the high torque despite the small size has contributed to the high-speed and quiet AF drive.
Installed on Canon’s EF lenses for AF actuation, the USM (Ultrasonic Motor) obtains its source of energy from ultrasonic vibrations by utilising the properties of the ceramic piezoelectric element as well as the elastic metal body, which changes in shape when voltage is applied.
There are three types of USM in total. Ring USM and Micro USM transform travelling waves generated by vibrations into rotational movement, and drive the focus lens to perform focusing. In contrast, Nano USM does not transform ultrasonic vibrations into rotational movement, but instead conveys straight-line motion directly to the focus lens that is connected by the rack component.
Ring USM generates a large torque by driving the lens elements with a large-sized rotor and stator, and is thus suitable for moving heavy lens elements. Meanwhile, Micro USM is highly versatile due to its compactness. Compared to these two types of USM, Nano USM is powerful despite its small size. It is suited for driving light focus lenses with a small lens diameter, and performs excellently during movie shooting. EF lenses employ these three sources of power for different purposes to achieve the highest level of performance.
B: Flange-shaped spring
C: Elastic metal body
D: Ceramic voltage element
The structure of Ring USM is very simple. It consists of a stator, which is an elastic metal body, and a rotor, which is a rotating body. Ultrasonic vibrations are generated by the stator to enable continuous rotation of the rotor.
Ring USM: Widely employed on large-aperture and super telephoto lenses
Ring USM drives the focus lens directly by making use of travelling waves generated by the toothed stator (elastic metal body + ceramic piezoelectric elements) to rotate the rotor continuously. Leveraging the characteristic that a high torque can be obtained from slow rotation, Ring USM is widely employed on lenses with heavy focus lenses, such as large-aperture and super telephoto lenses.
Micro USM (left) and Micro USM II (right): Used on prime lenses and others
Similar to the principle of Ring USM, which makes use of ultrasonic vibrations, roll movement that is generated inside the unit is transformed into rotational movement for driving the lens elements through the gear unit. Compact in size, the unit is employed on small lenses such as prime lenses. Micro USM II is a downsized version of Micro USM.
Nano USM: The latest USM
Shaped like a computer chip, Nano USM forms a pair with the ceramic piezoelectric element and directly moves the focus lens that is supported by a guide bar in the back-and-forth direction. As there is no need to transform ultrasonic vibrations into rotary action, it does not require a mechanism as complex as that of Ring USM. As of June 2016, Nano USM is adopted on the EF-S18-135mm f/3.5-5.6 IS USM.
Feature 2: Its focusing mechanism is suited for high-precision and minute actuation
The most outstanding feature of Nano USM is that ultrasonic vibrations are utilised directly in straight-line motion without being transformed into rotational movement. This characteristic enhances the start and stop responsiveness, thus enabling smooth AF drive.
One mechanical characteristic of Nano USM is that the focus lens is supported by a guide bar. This is similar to the lead-screw type STM (Stepping Motor) that is employed on lenses such as the EF-S18-135mm f/3.5-5.6 IS STM. Adopting such a mechanism eliminates the need of a cam, and thus has the advantage of achieving a compact size. As the load of the guide-bar support mechanism is minimal during focus lens drive, this makes it suitable for high-precision and minute actuation.
A: Guide Bar
B: Stepping Motor
C: Focus Lens
D: Lead-type Screw
E: Rack Component
STM is a motor that functions using pulse signals, and thus excels in the transmission of minute movements. Operating sound during focusing is almost non-existent, making it an actuator that is well suited for movie shooting, which requires the focusing mechanism to operate at all times.
Nano USM offers quiet operation with almost no operating sound during AF drive, and this comes in handy for different types of shoots. Also, high-speed and high-response AF shooting is possible as the source of power is connected directly to the drive unit without the use of a gear. Capable of driving focus lenses efficiently, Nano USM is a motor that is suited for focus lens groups that move a longer distance, such as super zoom and super telephoto lenses. It is also one of the actuators that match well with the inner focusing and rear focusing systems with a light focus lens group.
> For more details on the inner focusing and rear focusing systems, please click the link below
Inner Focusing, Rear Focusing
The strengths of Nano USM – through actual images
Quiet focusing mechanism is idea for scenes where silence is paramount
EOS 80D/ EF-S18-135mm f/3.5-5.6 IS USM/ FL: 76mm (122mm equivalent)/ Aperture-priority AE (f/8, 1/400 sec., EV±0)/ ISO 400/ WB: Daylight
In wildlife photography where animals would react to the slightest noise, the quiet focusing mechanism of Nano USM comes in extremely handy especially when you're shooting up close. By turning off the beeper sound on the camera, you can achieve focus quietly to capture natural shots of the animals.
High-speed AF captures the fleeting expressions
EOS 80D/ EF-S18-135mm f/3.5-5.6 IS USM/ FL: 112mm (equivalent to 179mm in 35mm format)/ Portrait (f/5.6, 1/160 sec., EV±0)/ ISO 800/ WB: Auto
A shorter focusing time helps to enhance the flow of the shoot, thus allowing you to bring out the natural expressions of the subject more easily. Particularly, Nano USM comes in handy when taking portrait shots of a subject with movement. It is also capable of capturing the slightest changes in the facial expression of the subject.
Nano USM takes AF photography to a new level
Though a newly-developed technology, the potential of Nano USM is immeasurable. As with Micro USM, one of its advantages as an actuator lies in the compact size, which allows for the downsizing and lightweight design of lenses. Also, Nano USM works well with Dual Pixel CMOS AF, which makes use of image plane phase difference detection AF. The AF speed when using the Live View function is comparable to that during viewfinder shooting, and this has helped to extend the use of the Live View function to new genres. In street and portrait photography, for example, Live View shooting has now become a main shooting technique.
Besides its use on super zoom lenses, we can also expect the introduction of Nano USM on compact telephoto lenses in future. Also, Nano USM allows for easy AF start and stop control, and is therefore likely to boost the development of an automatic bracketing function for the focusing point. The birth of the new actuator will no doubt garner wide attention as a technology that takes AF photography to a new level.
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Born in Aichi in 1960, Takahashi started his freelance career in 1987 after working with an advertising photo studio and a publishing house. Photographing for major magazines, he has travelled to many parts of the world from his bases in Japan and China. Takahashi is a member of the Japan Professional Photographers Society (JPS).